1 2********************* 3GNU Parallel Tutorial 4********************* 5 6 7This tutorial shows off much of GNU \ **parallel**\ 's functionality. The 8tutorial is meant to learn the options in and syntax of GNU 9\ **parallel**\ . The tutorial is \ **not**\ to show realistic examples from the 10real world. 11 12Reader's guide 13============== 14 15 16If you prefer reading a book buy \ **GNU Parallel 2018**\ at 17https://www.lulu.com/shop/ole-tange/gnu-parallel-2018/paperback/product-23558902.html 18or download it at: https://doi.org/10.5281/zenodo.1146014 19 20Otherwise start by watching the intro videos for a quick introduction: 21https://www.youtube.com/playlist?list=PL284C9FF2488BC6D1 22 23Then browse through the \ **EXAMPLE**\ s after the list of \ **OPTIONS**\ in 24\ **man parallel**\ (Use \ **LESS=+/EXAMPLE: man parallel**\ ). That will give 25you an idea of what GNU \ **parallel**\ is capable of. 26 27If you want to dive even deeper: spend a couple of hours walking 28through the tutorial (\ **man parallel_tutorial**\ ). Your command line 29will love you for it. 30 31Finally you may want to look at the rest of the manual (\ **man 32parallel**\ ) if you have special needs not already covered. 33 34If you want to know the design decisions behind GNU \ **parallel**\ , try: 35\ **man parallel_design**\ . This is also a good intro if you intend to 36change GNU \ **parallel**\ . 37 38 39 40************* 41Prerequisites 42************* 43 44 45To run this tutorial you must have the following: 46 47 48- parallel >= version 20160822 49 50 Install the newest version using your package manager (recommended for 51 security reasons), the way described in README, or with this command: 52 53 54 .. code-block:: perl 55 56 $ (wget -O - pi.dk/3 || lynx -source pi.dk/3 || curl pi.dk/3/ || \ 57 fetch -o - http://pi.dk/3 ) > install.sh 58 $ sha1sum install.sh 59 12345678 3374ec53 bacb199b 245af2dd a86df6c9 60 $ md5sum install.sh 61 029a9ac0 6e8b5bc6 052eac57 b2c3c9ca 62 $ sha512sum install.sh 63 40f53af6 9e20dae5 713ba06c f517006d 9897747b ed8a4694 b1acba1b 1464beb4 64 60055629 3f2356f3 3e9c4e3c 76e3f3af a9db4b32 bd33322b 975696fc e6b23cfb 65 $ bash install.sh 66 67 68 This will also install the newest version of the tutorial which you 69 can see by running this: 70 71 72 .. code-block:: perl 73 74 man parallel_tutorial 75 76 77 Most of the tutorial will work on older versions, too. 78 79 80 81- abc-file: 82 83 The file can be generated by this command: 84 85 86 .. code-block:: perl 87 88 parallel -k echo ::: A B C > abc-file 89 90 91 92 93- def-file: 94 95 The file can be generated by this command: 96 97 98 .. code-block:: perl 99 100 parallel -k echo ::: D E F > def-file 101 102 103 104 105- abc0-file: 106 107 The file can be generated by this command: 108 109 110 .. code-block:: perl 111 112 perl -e 'printf "A\0B\0C\0"' > abc0-file 113 114 115 116 117- abc_-file: 118 119 The file can be generated by this command: 120 121 122 .. code-block:: perl 123 124 perl -e 'printf "A_B_C_"' > abc_-file 125 126 127 128 129- tsv-file.tsv 130 131 The file can be generated by this command: 132 133 134 .. code-block:: perl 135 136 perl -e 'printf "f1\tf2\nA\tB\nC\tD\n"' > tsv-file.tsv 137 138 139 140 141- num8 142 143 The file can be generated by this command: 144 145 146 .. code-block:: perl 147 148 perl -e 'for(1..8){print "$_\n"}' > num8 149 150 151 152 153- num128 154 155 The file can be generated by this command: 156 157 158 .. code-block:: perl 159 160 perl -e 'for(1..128){print "$_\n"}' > num128 161 162 163 164 165- num30000 166 167 The file can be generated by this command: 168 169 170 .. code-block:: perl 171 172 perl -e 'for(1..30000){print "$_\n"}' > num30000 173 174 175 176 177- num1000000 178 179 The file can be generated by this command: 180 181 182 .. code-block:: perl 183 184 perl -e 'for(1..1000000){print "$_\n"}' > num1000000 185 186 187 188 189- num_%header 190 191 The file can be generated by this command: 192 193 194 .. code-block:: perl 195 196 (echo %head1; echo %head2; \ 197 perl -e 'for(1..10){print "$_\n"}') > num_%header 198 199 200 201 202- fixedlen 203 204 The file can be generated by this command: 205 206 207 .. code-block:: perl 208 209 perl -e 'print "HHHHAAABBBCCC"' > fixedlen 210 211 212 213 214- For remote running: ssh login on 2 servers with no password in $SERVER1 and $SERVER2 must work. 215 216 217 .. code-block:: perl 218 219 SERVER1=server.example.com 220 SERVER2=server2.example.net 221 222 223 So you must be able to do this without entering a password: 224 225 226 .. code-block:: perl 227 228 ssh $SERVER1 echo works 229 ssh $SERVER2 echo works 230 231 232 It can be setup by running 'ssh-keygen -t dsa; ssh-copy-id $SERVER1' 233 and using an empty passphrase, or you can use \ **ssh-agent**\ . 234 235 236 237 238************* 239Input sources 240************* 241 242 243GNU \ **parallel**\ reads input from input sources. These can be files, the 244command line, and stdin (standard input or a pipe). 245 246A single input source 247===================== 248 249 250Input can be read from the command line: 251 252 253.. code-block:: perl 254 255 parallel echo ::: A B C 256 257 258Output (the order may be different because the jobs are run in 259parallel): 260 261 262.. code-block:: perl 263 264 A 265 B 266 C 267 268 269The input source can be a file: 270 271 272.. code-block:: perl 273 274 parallel -a abc-file echo 275 276 277Output: Same as above. 278 279STDIN (standard input) can be the input source: 280 281 282.. code-block:: perl 283 284 cat abc-file | parallel echo 285 286 287Output: Same as above. 288 289 290Multiple input sources 291====================== 292 293 294GNU \ **parallel**\ can take multiple input sources given on the command 295line. GNU \ **parallel**\ then generates all combinations of the input 296sources: 297 298 299.. code-block:: perl 300 301 parallel echo ::: A B C ::: D E F 302 303 304Output (the order may be different): 305 306 307.. code-block:: perl 308 309 A D 310 A E 311 A F 312 B D 313 B E 314 B F 315 C D 316 C E 317 C F 318 319 320The input sources can be files: 321 322 323.. code-block:: perl 324 325 parallel -a abc-file -a def-file echo 326 327 328Output: Same as above. 329 330STDIN (standard input) can be one of the input sources using \ **-**\ : 331 332 333.. code-block:: perl 334 335 cat abc-file | parallel -a - -a def-file echo 336 337 338Output: Same as above. 339 340Instead of \ **-a**\ files can be given after \ **::::**\ : 341 342 343.. code-block:: perl 344 345 cat abc-file | parallel echo :::: - def-file 346 347 348Output: Same as above. 349 350::: and :::: can be mixed: 351 352 353.. code-block:: perl 354 355 parallel echo ::: A B C :::: def-file 356 357 358Output: Same as above. 359 360Linking arguments from input sources 361------------------------------------ 362 363 364With \ **--link**\ you can link the input sources and get one argument 365from each input source: 366 367 368.. code-block:: perl 369 370 parallel --link echo ::: A B C ::: D E F 371 372 373Output (the order may be different): 374 375 376.. code-block:: perl 377 378 A D 379 B E 380 C F 381 382 383If one of the input sources is too short, its values will wrap: 384 385 386.. code-block:: perl 387 388 parallel --link echo ::: A B C D E ::: F G 389 390 391Output (the order may be different): 392 393 394.. code-block:: perl 395 396 A F 397 B G 398 C F 399 D G 400 E F 401 402 403For more flexible linking you can use \ **:::+**\ and \ **::::+**\ . They work 404like \ **:::**\ and \ **::::**\ except they link the previous input source to 405this input source. 406 407This will link ABC to GHI: 408 409 410.. code-block:: perl 411 412 parallel echo :::: abc-file :::+ G H I :::: def-file 413 414 415Output (the order may be different): 416 417 418.. code-block:: perl 419 420 A G D 421 A G E 422 A G F 423 B H D 424 B H E 425 B H F 426 C I D 427 C I E 428 C I F 429 430 431This will link GHI to DEF: 432 433 434.. code-block:: perl 435 436 parallel echo :::: abc-file ::: G H I ::::+ def-file 437 438 439Output (the order may be different): 440 441 442.. code-block:: perl 443 444 A G D 445 A H E 446 A I F 447 B G D 448 B H E 449 B I F 450 C G D 451 C H E 452 C I F 453 454 455If one of the input sources is too short when using \ **:::+**\ or 456\ **::::+**\ , the rest will be ignored: 457 458 459.. code-block:: perl 460 461 parallel echo ::: A B C D E :::+ F G 462 463 464Output (the order may be different): 465 466 467.. code-block:: perl 468 469 A F 470 B G 471 472 473 474 475Changing the argument separator. 476================================ 477 478 479GNU \ **parallel**\ can use other separators than \ **:::**\ or \ **::::**\ . This is 480typically useful if \ **:::**\ or \ **::::**\ is used in the command to run: 481 482 483.. code-block:: perl 484 485 parallel --arg-sep ,, echo ,, A B C :::: def-file 486 487 488Output (the order may be different): 489 490 491.. code-block:: perl 492 493 A D 494 A E 495 A F 496 B D 497 B E 498 B F 499 C D 500 C E 501 C F 502 503 504Changing the argument file separator: 505 506 507.. code-block:: perl 508 509 parallel --arg-file-sep // echo ::: A B C // def-file 510 511 512Output: Same as above. 513 514 515Changing the argument delimiter 516=============================== 517 518 519GNU \ **parallel**\ will normally treat a full line as a single argument: It 520uses \ **\n**\ as argument delimiter. This can be changed with \ **-d**\ : 521 522 523.. code-block:: perl 524 525 parallel -d _ echo :::: abc_-file 526 527 528Output (the order may be different): 529 530 531.. code-block:: perl 532 533 A 534 B 535 C 536 537 538NUL can be given as \ **\0**\ : 539 540 541.. code-block:: perl 542 543 parallel -d '\0' echo :::: abc0-file 544 545 546Output: Same as above. 547 548A shorthand for \ **-d '\0'**\ is \ **-0**\ (this will often be used to read files 549from \ **find ... -print0**\ ): 550 551 552.. code-block:: perl 553 554 parallel -0 echo :::: abc0-file 555 556 557Output: Same as above. 558 559 560End-of-file value for input source 561================================== 562 563 564GNU \ **parallel**\ can stop reading when it encounters a certain value: 565 566 567.. code-block:: perl 568 569 parallel -E stop echo ::: A B stop C D 570 571 572Output: 573 574 575.. code-block:: perl 576 577 A 578 B 579 580 581 582Skipping empty lines 583==================== 584 585 586Using \ **--no-run-if-empty**\ GNU \ **parallel**\ will skip empty lines. 587 588 589.. code-block:: perl 590 591 (echo 1; echo; echo 2) | parallel --no-run-if-empty echo 592 593 594Output: 595 596 597.. code-block:: perl 598 599 1 600 2 601 602 603 604 605************************* 606Building the command line 607************************* 608 609 610No command means arguments are commands 611======================================= 612 613 614If no command is given after parallel the arguments themselves are 615treated as commands: 616 617 618.. code-block:: perl 619 620 parallel ::: ls 'echo foo' pwd 621 622 623Output (the order may be different): 624 625 626.. code-block:: perl 627 628 [list of files in current dir] 629 foo 630 [/path/to/current/working/dir] 631 632 633The command can be a script, a binary or a Bash function if the function is 634exported using \ **export -f**\ : 635 636 637.. code-block:: perl 638 639 # Only works in Bash 640 my_func() { 641 echo in my_func $1 642 } 643 export -f my_func 644 parallel my_func ::: 1 2 3 645 646 647Output (the order may be different): 648 649 650.. code-block:: perl 651 652 in my_func 1 653 in my_func 2 654 in my_func 3 655 656 657 658Replacement strings 659=================== 660 661 662The 7 predefined replacement strings 663------------------------------------ 664 665 666GNU \ **parallel**\ has several replacement strings. If no replacement 667strings are used the default is to append \ **{}**\ : 668 669 670.. code-block:: perl 671 672 parallel echo ::: A/B.C 673 674 675Output: 676 677 678.. code-block:: perl 679 680 A/B.C 681 682 683The default replacement string is \ **{}**\ : 684 685 686.. code-block:: perl 687 688 parallel echo {} ::: A/B.C 689 690 691Output: 692 693 694.. code-block:: perl 695 696 A/B.C 697 698 699The replacement string \ **{.}**\ removes the extension: 700 701 702.. code-block:: perl 703 704 parallel echo {.} ::: A/B.C 705 706 707Output: 708 709 710.. code-block:: perl 711 712 A/B 713 714 715The replacement string \ **{/}**\ removes the path: 716 717 718.. code-block:: perl 719 720 parallel echo {/} ::: A/B.C 721 722 723Output: 724 725 726.. code-block:: perl 727 728 B.C 729 730 731The replacement string \ **{//}**\ keeps only the path: 732 733 734.. code-block:: perl 735 736 parallel echo {//} ::: A/B.C 737 738 739Output: 740 741 742.. code-block:: perl 743 744 A 745 746 747The replacement string \ **{/.}**\ removes the path and the extension: 748 749 750.. code-block:: perl 751 752 parallel echo {/.} ::: A/B.C 753 754 755Output: 756 757 758.. code-block:: perl 759 760 B 761 762 763The replacement string \ **{#}**\ gives the job number: 764 765 766.. code-block:: perl 767 768 parallel echo {#} ::: A B C 769 770 771Output (the order may be different): 772 773 774.. code-block:: perl 775 776 1 777 2 778 3 779 780 781The replacement string \ **{%}**\ gives the job slot number (between 1 and 782number of jobs to run in parallel): 783 784 785.. code-block:: perl 786 787 parallel -j 2 echo {%} ::: A B C 788 789 790Output (the order may be different and 1 and 2 may be swapped): 791 792 793.. code-block:: perl 794 795 1 796 2 797 1 798 799 800 801Changing the replacement strings 802-------------------------------- 803 804 805The replacement string \ **{}**\ can be changed with \ **-I**\ : 806 807 808.. code-block:: perl 809 810 parallel -I ,, echo ,, ::: A/B.C 811 812 813Output: 814 815 816.. code-block:: perl 817 818 A/B.C 819 820 821The replacement string \ **{.}**\ can be changed with \ **--extensionreplace**\ : 822 823 824.. code-block:: perl 825 826 parallel --extensionreplace ,, echo ,, ::: A/B.C 827 828 829Output: 830 831 832.. code-block:: perl 833 834 A/B 835 836 837The replacement string \ **{/}**\ can be replaced with \ **--basenamereplace**\ : 838 839 840.. code-block:: perl 841 842 parallel --basenamereplace ,, echo ,, ::: A/B.C 843 844 845Output: 846 847 848.. code-block:: perl 849 850 B.C 851 852 853The replacement string \ **{//}**\ can be changed with \ **--dirnamereplace**\ : 854 855 856.. code-block:: perl 857 858 parallel --dirnamereplace ,, echo ,, ::: A/B.C 859 860 861Output: 862 863 864.. code-block:: perl 865 866 A 867 868 869The replacement string \ **{/.}**\ can be changed with \ **--basenameextensionreplace**\ : 870 871 872.. code-block:: perl 873 874 parallel --basenameextensionreplace ,, echo ,, ::: A/B.C 875 876 877Output: 878 879 880.. code-block:: perl 881 882 B 883 884 885The replacement string \ **{#}**\ can be changed with \ **--seqreplace**\ : 886 887 888.. code-block:: perl 889 890 parallel --seqreplace ,, echo ,, ::: A B C 891 892 893Output (the order may be different): 894 895 896.. code-block:: perl 897 898 1 899 2 900 3 901 902 903The replacement string \ **{%}**\ can be changed with \ **--slotreplace**\ : 904 905 906.. code-block:: perl 907 908 parallel -j2 --slotreplace ,, echo ,, ::: A B C 909 910 911Output (the order may be different and 1 and 2 may be swapped): 912 913 914.. code-block:: perl 915 916 1 917 2 918 1 919 920 921 922Perl expression replacement string 923---------------------------------- 924 925 926When predefined replacement strings are not flexible enough a perl 927expression can be used instead. One example is to remove two 928extensions: foo.tar.gz becomes foo 929 930 931.. code-block:: perl 932 933 parallel echo '{= s:\.[^.]+$::;s:\.[^.]+$::; =}' ::: foo.tar.gz 934 935 936Output: 937 938 939.. code-block:: perl 940 941 foo 942 943 944In \ **{= =}**\ you can access all of GNU \ **parallel**\ 's internal functions 945and variables. A few are worth mentioning. 946 947\ **total_jobs()**\ returns the total number of jobs: 948 949 950.. code-block:: perl 951 952 parallel echo Job {#} of {= '$_=total_jobs()' =} ::: {1..5} 953 954 955Output: 956 957 958.. code-block:: perl 959 960 Job 1 of 5 961 Job 2 of 5 962 Job 3 of 5 963 Job 4 of 5 964 Job 5 of 5 965 966 967\ **Q(...)**\ shell quotes the string: 968 969 970.. code-block:: perl 971 972 parallel echo {} shell quoted is {= '$_=Q($_)' =} ::: '*/!#$' 973 974 975Output: 976 977 978.. code-block:: perl 979 980 */!#$ shell quoted is \*/\!\#\$ 981 982 983\ **skip()**\ skips the job: 984 985 986.. code-block:: perl 987 988 parallel echo {= 'if($_==3) { skip() }' =} ::: {1..5} 989 990 991Output: 992 993 994.. code-block:: perl 995 996 1 997 2 998 4 999 5 1000 1001 1002\ **@arg**\ contains the input source variables: 1003 1004 1005.. code-block:: perl 1006 1007 parallel echo {= 'if($arg[1]==$arg[2]) { skip() }' =} \ 1008 ::: {1..3} ::: {1..3} 1009 1010 1011Output: 1012 1013 1014.. code-block:: perl 1015 1016 1 2 1017 1 3 1018 2 1 1019 2 3 1020 3 1 1021 3 2 1022 1023 1024If the strings \ **{=**\ and \ **=}**\ cause problems they can be replaced with \ **--parens**\ : 1025 1026 1027.. code-block:: perl 1028 1029 parallel --parens ,,,, echo ',, s:\.[^.]+$::;s:\.[^.]+$::; ,,' \ 1030 ::: foo.tar.gz 1031 1032 1033Output: 1034 1035 1036.. code-block:: perl 1037 1038 foo 1039 1040 1041To define a shorthand replacement string use \ **--rpl**\ : 1042 1043 1044.. code-block:: perl 1045 1046 parallel --rpl '.. s:\.[^.]+$::;s:\.[^.]+$::;' echo '..' \ 1047 ::: foo.tar.gz 1048 1049 1050Output: Same as above. 1051 1052If the shorthand starts with \ **{**\ it can be used as a positional 1053replacement string, too: 1054 1055 1056.. code-block:: perl 1057 1058 parallel --rpl '{..} s:\.[^.]+$::;s:\.[^.]+$::;' echo '{..}' 1059 ::: foo.tar.gz 1060 1061 1062Output: Same as above. 1063 1064If the shorthand contains matching parenthesis the replacement string 1065becomes a dynamic replacement string and the string in the parenthesis 1066can be accessed as $$1. If there are multiple matching parenthesis, 1067the matched strings can be accessed using $$2, $$3 and so on. 1068 1069You can think of this as giving arguments to the replacement 1070string. Here we give the argument \ **.tar.gz**\ to the replacement string 1071\ **{%\ \*string\*\ }**\ which removes \ *string*\ : 1072 1073 1074.. code-block:: perl 1075 1076 parallel --rpl '{%(.+?)} s/$$1$//;' echo {%.tar.gz}.zip ::: foo.tar.gz 1077 1078 1079Output: 1080 1081 1082.. code-block:: perl 1083 1084 foo.zip 1085 1086 1087Here we give the two arguments \ **tar.gz**\ and \ **zip**\ to the replacement 1088string \ **{/\ \*string1\*\ /\ \*string2\*\ }**\ which replaces \ *string1*\ with 1089\ *string2*\ : 1090 1091 1092.. code-block:: perl 1093 1094 parallel --rpl '{/(.+?)/(.*?)} s/$$1/$$2/;' echo {/tar.gz/zip} \ 1095 ::: foo.tar.gz 1096 1097 1098Output: 1099 1100 1101.. code-block:: perl 1102 1103 foo.zip 1104 1105 1106GNU \ **parallel**\ 's 7 replacement strings are implemented as this: 1107 1108 1109.. code-block:: perl 1110 1111 --rpl '{} ' 1112 --rpl '{#} $_=$job->seq()' 1113 --rpl '{%} $_=$job->slot()' 1114 --rpl '{/} s:.*/::' 1115 --rpl '{//} $Global::use{"File::Basename"} ||= 1116 eval "use File::Basename; 1;"; $_ = dirname($_);' 1117 --rpl '{/.} s:.*/::; s:\.[^/.]+$::;' 1118 --rpl '{.} s:\.[^/.]+$::' 1119 1120 1121 1122Positional replacement strings 1123------------------------------ 1124 1125 1126With multiple input sources the argument from the individual input 1127sources can be accessed with \ **{**\ number\ **}**\ : 1128 1129 1130.. code-block:: perl 1131 1132 parallel echo {1} and {2} ::: A B ::: C D 1133 1134 1135Output (the order may be different): 1136 1137 1138.. code-block:: perl 1139 1140 A and C 1141 A and D 1142 B and C 1143 B and D 1144 1145 1146The positional replacement strings can also be modified using \ **/**\ , \ **//**\ , \ **/.**\ , and \ **.**\ : 1147 1148 1149.. code-block:: perl 1150 1151 parallel echo /={1/} //={1//} /.={1/.} .={1.} ::: A/B.C D/E.F 1152 1153 1154Output (the order may be different): 1155 1156 1157.. code-block:: perl 1158 1159 /=B.C //=A /.=B .=A/B 1160 /=E.F //=D /.=E .=D/E 1161 1162 1163If a position is negative, it will refer to the input source counted 1164from behind: 1165 1166 1167.. code-block:: perl 1168 1169 parallel echo 1={1} 2={2} 3={3} -1={-1} -2={-2} -3={-3} \ 1170 ::: A B ::: C D ::: E F 1171 1172 1173Output (the order may be different): 1174 1175 1176.. code-block:: perl 1177 1178 1=A 2=C 3=E -1=E -2=C -3=A 1179 1=A 2=C 3=F -1=F -2=C -3=A 1180 1=A 2=D 3=E -1=E -2=D -3=A 1181 1=A 2=D 3=F -1=F -2=D -3=A 1182 1=B 2=C 3=E -1=E -2=C -3=B 1183 1=B 2=C 3=F -1=F -2=C -3=B 1184 1=B 2=D 3=E -1=E -2=D -3=B 1185 1=B 2=D 3=F -1=F -2=D -3=B 1186 1187 1188 1189Positional perl expression replacement string 1190--------------------------------------------- 1191 1192 1193To use a perl expression as a positional replacement string simply 1194prepend the perl expression with number and space: 1195 1196 1197.. code-block:: perl 1198 1199 parallel echo '{=2 s:\.[^.]+$::;s:\.[^.]+$::; =} {1}' \ 1200 ::: bar ::: foo.tar.gz 1201 1202 1203Output: 1204 1205 1206.. code-block:: perl 1207 1208 foo bar 1209 1210 1211If a shorthand defined using \ **--rpl**\ starts with \ **{**\ it can be used as 1212a positional replacement string, too: 1213 1214 1215.. code-block:: perl 1216 1217 parallel --rpl '{..} s:\.[^.]+$::;s:\.[^.]+$::;' echo '{2..} {1}' \ 1218 ::: bar ::: foo.tar.gz 1219 1220 1221Output: Same as above. 1222 1223 1224Input from columns 1225------------------ 1226 1227 1228The columns in a file can be bound to positional replacement strings 1229using \ **--colsep**\ . Here the columns are separated by TAB (\t): 1230 1231 1232.. code-block:: perl 1233 1234 parallel --colsep '\t' echo 1={1} 2={2} :::: tsv-file.tsv 1235 1236 1237Output (the order may be different): 1238 1239 1240.. code-block:: perl 1241 1242 1=f1 2=f2 1243 1=A 2=B 1244 1=C 2=D 1245 1246 1247 1248Header defined replacement strings 1249---------------------------------- 1250 1251 1252With \ **--header**\ GNU \ **parallel**\ will use the first value of the input 1253source as the name of the replacement string. Only the non-modified 1254version \ **{}**\ is supported: 1255 1256 1257.. code-block:: perl 1258 1259 parallel --header : echo f1={f1} f2={f2} ::: f1 A B ::: f2 C D 1260 1261 1262Output (the order may be different): 1263 1264 1265.. code-block:: perl 1266 1267 f1=A f2=C 1268 f1=A f2=D 1269 f1=B f2=C 1270 f1=B f2=D 1271 1272 1273It is useful with \ **--colsep**\ for processing files with TAB separated values: 1274 1275 1276.. code-block:: perl 1277 1278 parallel --header : --colsep '\t' echo f1={f1} f2={f2} \ 1279 :::: tsv-file.tsv 1280 1281 1282Output (the order may be different): 1283 1284 1285.. code-block:: perl 1286 1287 f1=A f2=B 1288 f1=C f2=D 1289 1290 1291 1292More pre-defined replacement strings with --plus 1293------------------------------------------------ 1294 1295 1296\ **--plus**\ adds the replacement strings \ **{+/} {+.} {+..} {+...} {..} {...} 1297{/..} {/...} {##}**\ . The idea being that \ **{+foo}**\ matches the opposite of \ **{foo}**\ 1298and \ **{}**\ = \ **{+/}**\ /\ **{/}**\ = \ **{.}**\ .\ **{+.}**\ = \ **{+/}**\ /\ **{/.}**\ .\ **{+.}**\ = \ **{..}**\ .\ **{+..}**\ = 1299\ **{+/}**\ /\ **{/..}**\ .\ **{+..}**\ = \ **{...}**\ .\ **{+...}**\ = \ **{+/}**\ /\ **{/...}**\ .\ **{+...}**\ . 1300 1301 1302.. code-block:: perl 1303 1304 parallel --plus echo {} ::: dir/sub/file.ex1.ex2.ex3 1305 parallel --plus echo {+/}/{/} ::: dir/sub/file.ex1.ex2.ex3 1306 parallel --plus echo {.}.{+.} ::: dir/sub/file.ex1.ex2.ex3 1307 parallel --plus echo {+/}/{/.}.{+.} ::: dir/sub/file.ex1.ex2.ex3 1308 parallel --plus echo {..}.{+..} ::: dir/sub/file.ex1.ex2.ex3 1309 parallel --plus echo {+/}/{/..}.{+..} ::: dir/sub/file.ex1.ex2.ex3 1310 parallel --plus echo {...}.{+...} ::: dir/sub/file.ex1.ex2.ex3 1311 parallel --plus echo {+/}/{/...}.{+...} ::: dir/sub/file.ex1.ex2.ex3 1312 1313 1314Output: 1315 1316 1317.. code-block:: perl 1318 1319 dir/sub/file.ex1.ex2.ex3 1320 1321 1322\ **{##}**\ is simply the number of jobs: 1323 1324 1325.. code-block:: perl 1326 1327 parallel --plus echo Job {#} of {##} ::: {1..5} 1328 1329 1330Output: 1331 1332 1333.. code-block:: perl 1334 1335 Job 1 of 5 1336 Job 2 of 5 1337 Job 3 of 5 1338 Job 4 of 5 1339 Job 5 of 5 1340 1341 1342 1343Dynamic replacement strings with --plus 1344--------------------------------------- 1345 1346 1347\ **--plus**\ also defines these dynamic replacement strings: 1348 1349 1350- \ **{:-\ \*string\*\ }**\ 1351 1352 Default value is \ *string*\ if the argument is empty. 1353 1354 1355 1356- \ **{:\ \*number\*\ }**\ 1357 1358 Substring from \ *number*\ till end of string. 1359 1360 1361 1362- \ **{:\ \*number1\*\ :\ \*number2\*\ }**\ 1363 1364 Substring from \ *number1*\ to \ *number2*\ . 1365 1366 1367 1368- \ **{#\ \*string\*\ }**\ 1369 1370 If the argument starts with \ *string*\ , remove it. 1371 1372 1373 1374- \ **{%\ \*string\*\ }**\ 1375 1376 If the argument ends with \ *string*\ , remove it. 1377 1378 1379 1380- \ **{/\ \*string1\*\ /\ \*string2\*\ }**\ 1381 1382 Replace \ *string1*\ with \ *string2*\ . 1383 1384 1385 1386- \ **{^\ \*string\*\ }**\ 1387 1388 If the argument starts with \ *string*\ , upper case it. \ *string*\ must 1389 be a single letter. 1390 1391 1392 1393- \ **{^^\ \*string\*\ }**\ 1394 1395 If the argument contains \ *string*\ , upper case it. \ *string*\ must be a 1396 single letter. 1397 1398 1399 1400- \ **{,\ \*string\*\ }**\ 1401 1402 If the argument starts with \ *string*\ , lower case it. \ *string*\ must 1403 be a single letter. 1404 1405 1406 1407- \ **{,,\ \*string\*\ }**\ 1408 1409 If the argument contains \ *string*\ , lower case it. \ *string*\ must be a 1410 single letter. 1411 1412 1413 1414They are inspired from \ **Bash**\ : 1415 1416 1417.. code-block:: perl 1418 1419 unset myvar 1420 echo ${myvar:-myval} 1421 parallel --plus echo {:-myval} ::: "$myvar" 1422 1423 myvar=abcAaAdef 1424 echo ${myvar:2} 1425 parallel --plus echo {:2} ::: "$myvar" 1426 1427 echo ${myvar:2:3} 1428 parallel --plus echo {:2:3} ::: "$myvar" 1429 1430 echo ${myvar#bc} 1431 parallel --plus echo {#bc} ::: "$myvar" 1432 echo ${myvar#abc} 1433 parallel --plus echo {#abc} ::: "$myvar" 1434 1435 echo ${myvar%de} 1436 parallel --plus echo {%de} ::: "$myvar" 1437 echo ${myvar%def} 1438 parallel --plus echo {%def} ::: "$myvar" 1439 1440 echo ${myvar/def/ghi} 1441 parallel --plus echo {/def/ghi} ::: "$myvar" 1442 1443 echo ${myvar^a} 1444 parallel --plus echo {^a} ::: "$myvar" 1445 echo ${myvar^^a} 1446 parallel --plus echo {^^a} ::: "$myvar" 1447 1448 myvar=AbcAaAdef 1449 echo ${myvar,A} 1450 parallel --plus echo '{,A}' ::: "$myvar" 1451 echo ${myvar,,A} 1452 parallel --plus echo '{,,A}' ::: "$myvar" 1453 1454 1455Output: 1456 1457 1458.. code-block:: perl 1459 1460 myval 1461 myval 1462 cAaAdef 1463 cAaAdef 1464 cAa 1465 cAa 1466 abcAaAdef 1467 abcAaAdef 1468 AaAdef 1469 AaAdef 1470 abcAaAdef 1471 abcAaAdef 1472 abcAaA 1473 abcAaA 1474 abcAaAghi 1475 abcAaAghi 1476 AbcAaAdef 1477 AbcAaAdef 1478 AbcAAAdef 1479 AbcAAAdef 1480 abcAaAdef 1481 abcAaAdef 1482 abcaaadef 1483 abcaaadef 1484 1485 1486 1487 1488More than one argument 1489====================== 1490 1491 1492With \ **--xargs**\ GNU \ **parallel**\ will fit as many arguments as possible on a 1493single line: 1494 1495 1496.. code-block:: perl 1497 1498 cat num30000 | parallel --xargs echo | wc -l 1499 1500 1501Output (if you run this under Bash on GNU/Linux): 1502 1503 1504.. code-block:: perl 1505 1506 2 1507 1508 1509The 30000 arguments fitted on 2 lines. 1510 1511The maximal length of a single line can be set with \ **-s**\ . With a maximal 1512line length of 10000 chars 17 commands will be run: 1513 1514 1515.. code-block:: perl 1516 1517 cat num30000 | parallel --xargs -s 10000 echo | wc -l 1518 1519 1520Output: 1521 1522 1523.. code-block:: perl 1524 1525 17 1526 1527 1528For better parallelism GNU \ **parallel**\ can distribute the arguments 1529between all the parallel jobs when end of file is met. 1530 1531Below GNU \ **parallel**\ reads the last argument when generating the second 1532job. When GNU \ **parallel**\ reads the last argument, it spreads all the 1533arguments for the second job over 4 jobs instead, as 4 parallel jobs 1534are requested. 1535 1536The first job will be the same as the \ **--xargs**\ example above, but the 1537second job will be split into 4 evenly sized jobs, resulting in a 1538total of 5 jobs: 1539 1540 1541.. code-block:: perl 1542 1543 cat num30000 | parallel --jobs 4 -m echo | wc -l 1544 1545 1546Output (if you run this under Bash on GNU/Linux): 1547 1548 1549.. code-block:: perl 1550 1551 5 1552 1553 1554This is even more visible when running 4 jobs with 10 arguments. The 155510 arguments are being spread over 4 jobs: 1556 1557 1558.. code-block:: perl 1559 1560 parallel --jobs 4 -m echo ::: 1 2 3 4 5 6 7 8 9 10 1561 1562 1563Output: 1564 1565 1566.. code-block:: perl 1567 1568 1 2 3 1569 4 5 6 1570 7 8 9 1571 10 1572 1573 1574A replacement string can be part of a word. \ **-m**\ will not repeat the context: 1575 1576 1577.. code-block:: perl 1578 1579 parallel --jobs 4 -m echo pre-{}-post ::: A B C D E F G 1580 1581 1582Output (the order may be different): 1583 1584 1585.. code-block:: perl 1586 1587 pre-A B-post 1588 pre-C D-post 1589 pre-E F-post 1590 pre-G-post 1591 1592 1593To repeat the context use \ **-X**\ which otherwise works like \ **-m**\ : 1594 1595 1596.. code-block:: perl 1597 1598 parallel --jobs 4 -X echo pre-{}-post ::: A B C D E F G 1599 1600 1601Output (the order may be different): 1602 1603 1604.. code-block:: perl 1605 1606 pre-A-post pre-B-post 1607 pre-C-post pre-D-post 1608 pre-E-post pre-F-post 1609 pre-G-post 1610 1611 1612To limit the number of arguments use \ **-N**\ : 1613 1614 1615.. code-block:: perl 1616 1617 parallel -N3 echo ::: A B C D E F G H 1618 1619 1620Output (the order may be different): 1621 1622 1623.. code-block:: perl 1624 1625 A B C 1626 D E F 1627 G H 1628 1629 1630\ **-N**\ also sets the positional replacement strings: 1631 1632 1633.. code-block:: perl 1634 1635 parallel -N3 echo 1={1} 2={2} 3={3} ::: A B C D E F G H 1636 1637 1638Output (the order may be different): 1639 1640 1641.. code-block:: perl 1642 1643 1=A 2=B 3=C 1644 1=D 2=E 3=F 1645 1=G 2=H 3= 1646 1647 1648\ **-N0**\ reads 1 argument but inserts none: 1649 1650 1651.. code-block:: perl 1652 1653 parallel -N0 echo foo ::: 1 2 3 1654 1655 1656Output: 1657 1658 1659.. code-block:: perl 1660 1661 foo 1662 foo 1663 foo 1664 1665 1666 1667Quoting 1668======= 1669 1670 1671Command lines that contain special characters may need to be protected from the shell. 1672 1673The \ **perl**\ program \ **print "@ARGV\n"**\ basically works like \ **echo**\ . 1674 1675 1676.. code-block:: perl 1677 1678 perl -e 'print "@ARGV\n"' A 1679 1680 1681Output: 1682 1683 1684.. code-block:: perl 1685 1686 A 1687 1688 1689To run that in parallel the command needs to be quoted: 1690 1691 1692.. code-block:: perl 1693 1694 parallel perl -e 'print "@ARGV\n"' ::: This wont work 1695 1696 1697Output: 1698 1699 1700.. code-block:: perl 1701 1702 [Nothing] 1703 1704 1705To quote the command use \ **-q**\ : 1706 1707 1708.. code-block:: perl 1709 1710 parallel -q perl -e 'print "@ARGV\n"' ::: This works 1711 1712 1713Output (the order may be different): 1714 1715 1716.. code-block:: perl 1717 1718 This 1719 works 1720 1721 1722Or you can quote the critical part using \ **\'**\ : 1723 1724 1725.. code-block:: perl 1726 1727 parallel perl -e \''print "@ARGV\n"'\' ::: This works, too 1728 1729 1730Output (the order may be different): 1731 1732 1733.. code-block:: perl 1734 1735 This 1736 works, 1737 too 1738 1739 1740GNU \ **parallel**\ can also \-quote full lines. Simply run this: 1741 1742 1743.. code-block:: perl 1744 1745 parallel --shellquote 1746 Warning: Input is read from the terminal. You either know what you 1747 Warning: are doing (in which case: YOU ARE AWESOME!) or you forgot 1748 Warning: ::: or :::: or to pipe data into parallel. If so 1749 Warning: consider going through the tutorial: man parallel_tutorial 1750 Warning: Press CTRL-D to exit. 1751 perl -e 'print "@ARGV\n"' 1752 [CTRL-D] 1753 1754 1755Output: 1756 1757 1758.. code-block:: perl 1759 1760 perl\ -e\ \'print\ \"@ARGV\\n\"\' 1761 1762 1763This can then be used as the command: 1764 1765 1766.. code-block:: perl 1767 1768 parallel perl\ -e\ \'print\ \"@ARGV\\n\"\' ::: This also works 1769 1770 1771Output (the order may be different): 1772 1773 1774.. code-block:: perl 1775 1776 This 1777 also 1778 works 1779 1780 1781 1782Trimming space 1783============== 1784 1785 1786Space can be trimmed on the arguments using \ **--trim**\ : 1787 1788 1789.. code-block:: perl 1790 1791 parallel --trim r echo pre-{}-post ::: ' A ' 1792 1793 1794Output: 1795 1796 1797.. code-block:: perl 1798 1799 pre- A-post 1800 1801 1802To trim on the left side: 1803 1804 1805.. code-block:: perl 1806 1807 parallel --trim l echo pre-{}-post ::: ' A ' 1808 1809 1810Output: 1811 1812 1813.. code-block:: perl 1814 1815 pre-A -post 1816 1817 1818To trim on the both sides: 1819 1820 1821.. code-block:: perl 1822 1823 parallel --trim lr echo pre-{}-post ::: ' A ' 1824 1825 1826Output: 1827 1828 1829.. code-block:: perl 1830 1831 pre-A-post 1832 1833 1834 1835Respecting the shell 1836==================== 1837 1838 1839This tutorial uses Bash as the shell. GNU \ **parallel**\ respects which 1840shell you are using, so in \ **zsh**\ you can do: 1841 1842 1843.. code-block:: perl 1844 1845 parallel echo \={} ::: zsh bash ls 1846 1847 1848Output: 1849 1850 1851.. code-block:: perl 1852 1853 /usr/bin/zsh 1854 /bin/bash 1855 /bin/ls 1856 1857 1858In \ **csh**\ you can do: 1859 1860 1861.. code-block:: perl 1862 1863 parallel 'set a="{}"; if( { test -d "$a" } ) echo "$a is a dir"' ::: * 1864 1865 1866Output: 1867 1868 1869.. code-block:: perl 1870 1871 [somedir] is a dir 1872 1873 1874This also becomes useful if you use GNU \ **parallel**\ in a shell script: 1875GNU \ **parallel**\ will use the same shell as the shell script. 1876 1877 1878 1879********************** 1880Controlling the output 1881********************** 1882 1883 1884The output can prefixed with the argument: 1885 1886 1887.. code-block:: perl 1888 1889 parallel --tag echo foo-{} ::: A B C 1890 1891 1892Output (the order may be different): 1893 1894 1895.. code-block:: perl 1896 1897 A foo-A 1898 B foo-B 1899 C foo-C 1900 1901 1902To prefix it with another string use \ **--tagstring**\ : 1903 1904 1905.. code-block:: perl 1906 1907 parallel --tagstring {}-bar echo foo-{} ::: A B C 1908 1909 1910Output (the order may be different): 1911 1912 1913.. code-block:: perl 1914 1915 A-bar foo-A 1916 B-bar foo-B 1917 C-bar foo-C 1918 1919 1920To see what commands will be run without running them use \ **--dryrun**\ : 1921 1922 1923.. code-block:: perl 1924 1925 parallel --dryrun echo {} ::: A B C 1926 1927 1928Output (the order may be different): 1929 1930 1931.. code-block:: perl 1932 1933 echo A 1934 echo B 1935 echo C 1936 1937 1938To print the command before running them use \ **--verbose**\ : 1939 1940 1941.. code-block:: perl 1942 1943 parallel --verbose echo {} ::: A B C 1944 1945 1946Output (the order may be different): 1947 1948 1949.. code-block:: perl 1950 1951 echo A 1952 echo B 1953 A 1954 echo C 1955 B 1956 C 1957 1958 1959GNU \ **parallel**\ will postpone the output until the command completes: 1960 1961 1962.. code-block:: perl 1963 1964 parallel -j2 'printf "%s-start\n%s" {} {}; 1965 sleep {};printf "%s\n" -middle;echo {}-end' ::: 4 2 1 1966 1967 1968Output: 1969 1970 1971.. code-block:: perl 1972 1973 2-start 1974 2-middle 1975 2-end 1976 1-start 1977 1-middle 1978 1-end 1979 4-start 1980 4-middle 1981 4-end 1982 1983 1984To get the output immediately use \ **--ungroup**\ : 1985 1986 1987.. code-block:: perl 1988 1989 parallel -j2 --ungroup 'printf "%s-start\n%s" {} {}; 1990 sleep {};printf "%s\n" -middle;echo {}-end' ::: 4 2 1 1991 1992 1993Output: 1994 1995 1996.. code-block:: perl 1997 1998 4-start 1999 42-start 2000 2-middle 2001 2-end 2002 1-start 2003 1-middle 2004 1-end 2005 -middle 2006 4-end 2007 2008 2009\ **--ungroup**\ is fast, but can cause half a line from one job to be mixed 2010with half a line of another job. That has happened in the second line, 2011where the line '4-middle' is mixed with '2-start'. 2012 2013To avoid this use \ **--linebuffer**\ : 2014 2015 2016.. code-block:: perl 2017 2018 parallel -j2 --linebuffer 'printf "%s-start\n%s" {} {}; 2019 sleep {};printf "%s\n" -middle;echo {}-end' ::: 4 2 1 2020 2021 2022Output: 2023 2024 2025.. code-block:: perl 2026 2027 4-start 2028 2-start 2029 2-middle 2030 2-end 2031 1-start 2032 1-middle 2033 1-end 2034 4-middle 2035 4-end 2036 2037 2038To force the output in the same order as the arguments use \ **--keep-order**\ /\ **-k**\ : 2039 2040 2041.. code-block:: perl 2042 2043 parallel -j2 -k 'printf "%s-start\n%s" {} {}; 2044 sleep {};printf "%s\n" -middle;echo {}-end' ::: 4 2 1 2045 2046 2047Output: 2048 2049 2050.. code-block:: perl 2051 2052 4-start 2053 4-middle 2054 4-end 2055 2-start 2056 2-middle 2057 2-end 2058 1-start 2059 1-middle 2060 1-end 2061 2062 2063Saving output into files 2064======================== 2065 2066 2067GNU \ **parallel**\ can save the output of each job into files: 2068 2069 2070.. code-block:: perl 2071 2072 parallel --files echo ::: A B C 2073 2074 2075Output will be similar to this: 2076 2077 2078.. code-block:: perl 2079 2080 /tmp/pAh6uWuQCg.par 2081 /tmp/opjhZCzAX4.par 2082 /tmp/W0AT_Rph2o.par 2083 2084 2085By default GNU \ **parallel**\ will cache the output in files in \ **/tmp**\ . This 2086can be changed by setting \ **$TMPDIR**\ or \ **--tmpdir**\ : 2087 2088 2089.. code-block:: perl 2090 2091 parallel --tmpdir /var/tmp --files echo ::: A B C 2092 2093 2094Output will be similar to this: 2095 2096 2097.. code-block:: perl 2098 2099 /var/tmp/N_vk7phQRc.par 2100 /var/tmp/7zA4Ccf3wZ.par 2101 /var/tmp/LIuKgF_2LP.par 2102 2103 2104Or: 2105 2106 2107.. code-block:: perl 2108 2109 TMPDIR=/var/tmp parallel --files echo ::: A B C 2110 2111 2112Output: Same as above. 2113 2114The output files can be saved in a structured way using \ **--results**\ : 2115 2116 2117.. code-block:: perl 2118 2119 parallel --results outdir echo ::: A B C 2120 2121 2122Output: 2123 2124 2125.. code-block:: perl 2126 2127 A 2128 B 2129 C 2130 2131 2132These files were also generated containing the standard output 2133(stdout), standard error (stderr), and the sequence number (seq): 2134 2135 2136.. code-block:: perl 2137 2138 outdir/1/A/seq 2139 outdir/1/A/stderr 2140 outdir/1/A/stdout 2141 outdir/1/B/seq 2142 outdir/1/B/stderr 2143 outdir/1/B/stdout 2144 outdir/1/C/seq 2145 outdir/1/C/stderr 2146 outdir/1/C/stdout 2147 2148 2149\ **--header :**\ will take the first value as name and use that in the 2150directory structure. This is useful if you are using multiple input 2151sources: 2152 2153 2154.. code-block:: perl 2155 2156 parallel --header : --results outdir echo ::: f1 A B ::: f2 C D 2157 2158 2159Generated files: 2160 2161 2162.. code-block:: perl 2163 2164 outdir/f1/A/f2/C/seq 2165 outdir/f1/A/f2/C/stderr 2166 outdir/f1/A/f2/C/stdout 2167 outdir/f1/A/f2/D/seq 2168 outdir/f1/A/f2/D/stderr 2169 outdir/f1/A/f2/D/stdout 2170 outdir/f1/B/f2/C/seq 2171 outdir/f1/B/f2/C/stderr 2172 outdir/f1/B/f2/C/stdout 2173 outdir/f1/B/f2/D/seq 2174 outdir/f1/B/f2/D/stderr 2175 outdir/f1/B/f2/D/stdout 2176 2177 2178The directories are named after the variables and their values. 2179 2180 2181 2182************************* 2183Controlling the execution 2184************************* 2185 2186 2187Number of simultaneous jobs 2188=========================== 2189 2190 2191The number of concurrent jobs is given with \ **--jobs**\ /\ **-j**\ : 2192 2193 2194.. code-block:: perl 2195 2196 /usr/bin/time parallel -N0 -j64 sleep 1 :::: num128 2197 2198 2199With 64 jobs in parallel the 128 \ **sleep**\ s will take 2-8 seconds to run - 2200depending on how fast your machine is. 2201 2202By default \ **--jobs**\ is the same as the number of CPU cores. So this: 2203 2204 2205.. code-block:: perl 2206 2207 /usr/bin/time parallel -N0 sleep 1 :::: num128 2208 2209 2210should take twice the time of running 2 jobs per CPU core: 2211 2212 2213.. code-block:: perl 2214 2215 /usr/bin/time parallel -N0 --jobs 200% sleep 1 :::: num128 2216 2217 2218\ **--jobs 0**\ will run as many jobs in parallel as possible: 2219 2220 2221.. code-block:: perl 2222 2223 /usr/bin/time parallel -N0 --jobs 0 sleep 1 :::: num128 2224 2225 2226which should take 1-7 seconds depending on how fast your machine is. 2227 2228\ **--jobs**\ can read from a file which is re-read when a job finishes: 2229 2230 2231.. code-block:: perl 2232 2233 echo 50% > my_jobs 2234 /usr/bin/time parallel -N0 --jobs my_jobs sleep 1 :::: num128 & 2235 sleep 1 2236 echo 0 > my_jobs 2237 wait 2238 2239 2240The first second only 50% of the CPU cores will run a job. Then \ **0**\ is 2241put into \ **my_jobs**\ and then the rest of the jobs will be started in 2242parallel. 2243 2244Instead of basing the percentage on the number of CPU cores 2245GNU \ **parallel**\ can base it on the number of CPUs: 2246 2247 2248.. code-block:: perl 2249 2250 parallel --use-cpus-instead-of-cores -N0 sleep 1 :::: num8 2251 2252 2253 2254Shuffle job order 2255================= 2256 2257 2258If you have many jobs (e.g. by multiple combinations of input 2259sources), it can be handy to shuffle the jobs, so you get different 2260values run. Use \ **--shuf**\ for that: 2261 2262 2263.. code-block:: perl 2264 2265 parallel --shuf echo ::: 1 2 3 ::: a b c ::: A B C 2266 2267 2268Output: 2269 2270 2271.. code-block:: perl 2272 2273 All combinations but different order for each run. 2274 2275 2276 2277Interactivity 2278============= 2279 2280 2281GNU \ **parallel**\ can ask the user if a command should be run using \ **--interactive**\ : 2282 2283 2284.. code-block:: perl 2285 2286 parallel --interactive echo ::: 1 2 3 2287 2288 2289Output: 2290 2291 2292.. code-block:: perl 2293 2294 echo 1 ?...y 2295 echo 2 ?...n 2296 1 2297 echo 3 ?...y 2298 3 2299 2300 2301GNU \ **parallel**\ can be used to put arguments on the command line for an 2302interactive command such as \ **emacs**\ to edit one file at a time: 2303 2304 2305.. code-block:: perl 2306 2307 parallel --tty emacs ::: 1 2 3 2308 2309 2310Or give multiple argument in one go to open multiple files: 2311 2312 2313.. code-block:: perl 2314 2315 parallel -X --tty vi ::: 1 2 3 2316 2317 2318 2319A terminal for every job 2320======================== 2321 2322 2323Using \ **--tmux**\ GNU \ **parallel**\ can start a terminal for every job run: 2324 2325 2326.. code-block:: perl 2327 2328 seq 10 20 | parallel --tmux 'echo start {}; sleep {}; echo done {}' 2329 2330 2331This will tell you to run something similar to: 2332 2333 2334.. code-block:: perl 2335 2336 tmux -S /tmp/tmsrPrO0 attach 2337 2338 2339Using normal \ **tmux**\ keystrokes (CTRL-b n or CTRL-b p) you can cycle 2340between windows of the running jobs. When a job is finished it will 2341pause for 10 seconds before closing the window. 2342 2343 2344Timing 2345====== 2346 2347 2348Some jobs do heavy I/O when they start. To avoid a thundering herd GNU 2349\ **parallel**\ can delay starting new jobs. \ **--delay**\ \ *X*\ will make 2350sure there is at least \ *X*\ seconds between each start: 2351 2352 2353.. code-block:: perl 2354 2355 parallel --delay 2.5 echo Starting {}\;date ::: 1 2 3 2356 2357 2358Output: 2359 2360 2361.. code-block:: perl 2362 2363 Starting 1 2364 Thu Aug 15 16:24:33 CEST 2013 2365 Starting 2 2366 Thu Aug 15 16:24:35 CEST 2013 2367 Starting 3 2368 Thu Aug 15 16:24:38 CEST 2013 2369 2370 2371If jobs taking more than a certain amount of time are known to fail, 2372they can be stopped with \ **--timeout**\ . The accuracy of \ **--timeout**\ is 23732 seconds: 2374 2375 2376.. code-block:: perl 2377 2378 parallel --timeout 4.1 sleep {}\; echo {} ::: 2 4 6 8 2379 2380 2381Output: 2382 2383 2384.. code-block:: perl 2385 2386 2 2387 4 2388 2389 2390GNU \ **parallel**\ can compute the median runtime for jobs and kill those 2391that take more than 200% of the median runtime: 2392 2393 2394.. code-block:: perl 2395 2396 parallel --timeout 200% sleep {}\; echo {} ::: 2.1 2.2 3 7 2.3 2397 2398 2399Output: 2400 2401 2402.. code-block:: perl 2403 2404 2.1 2405 2.2 2406 3 2407 2.3 2408 2409 2410 2411Progress information 2412==================== 2413 2414 2415Based on the runtime of completed jobs GNU \ **parallel**\ can estimate the 2416total runtime: 2417 2418 2419.. code-block:: perl 2420 2421 parallel --eta sleep ::: 1 3 2 2 1 3 3 2 1 2422 2423 2424Output: 2425 2426 2427.. code-block:: perl 2428 2429 Computers / CPU cores / Max jobs to run 2430 1:local / 2 / 2 2431 2432 Computer:jobs running/jobs completed/%of started jobs/ 2433 Average seconds to complete 2434 ETA: 2s 0left 1.11avg local:0/9/100%/1.1s 2435 2436 2437GNU \ **parallel**\ can give progress information with \ **--progress**\ : 2438 2439 2440.. code-block:: perl 2441 2442 parallel --progress sleep ::: 1 3 2 2 1 3 3 2 1 2443 2444 2445Output: 2446 2447 2448.. code-block:: perl 2449 2450 Computers / CPU cores / Max jobs to run 2451 1:local / 2 / 2 2452 2453 Computer:jobs running/jobs completed/%of started jobs/ 2454 Average seconds to complete 2455 local:0/9/100%/1.1s 2456 2457 2458A progress bar can be shown with \ **--bar**\ : 2459 2460 2461.. code-block:: perl 2462 2463 parallel --bar sleep ::: 1 3 2 2 1 3 3 2 1 2464 2465 2466And a graphic bar can be shown with \ **--bar**\ and \ **zenity**\ : 2467 2468 2469.. code-block:: perl 2470 2471 seq 1000 | parallel -j10 --bar '(echo -n {};sleep 0.1)' \ 2472 2> >(perl -pe 'BEGIN{$/="\r";$|=1};s/\r/\n/g' | 2473 zenity --progress --auto-kill --auto-close) 2474 2475 2476A logfile of the jobs completed so far can be generated with \ **--joblog**\ : 2477 2478 2479.. code-block:: perl 2480 2481 parallel --joblog /tmp/log exit ::: 1 2 3 0 2482 cat /tmp/log 2483 2484 2485Output: 2486 2487 2488.. code-block:: perl 2489 2490 Seq Host Starttime Runtime Send Receive Exitval Signal Command 2491 1 : 1376577364.974 0.008 0 0 1 0 exit 1 2492 2 : 1376577364.982 0.013 0 0 2 0 exit 2 2493 3 : 1376577364.990 0.013 0 0 3 0 exit 3 2494 4 : 1376577365.003 0.003 0 0 0 0 exit 0 2495 2496 2497The log contains the job sequence, which host the job was run on, the 2498start time and run time, how much data was transferred, the exit 2499value, the signal that killed the job, and finally the command being 2500run. 2501 2502With a joblog GNU \ **parallel**\ can be stopped and later pickup where it 2503left off. It it important that the input of the completed jobs is 2504unchanged. 2505 2506 2507.. code-block:: perl 2508 2509 parallel --joblog /tmp/log exit ::: 1 2 3 0 2510 cat /tmp/log 2511 parallel --resume --joblog /tmp/log exit ::: 1 2 3 0 0 0 2512 cat /tmp/log 2513 2514 2515Output: 2516 2517 2518.. code-block:: perl 2519 2520 Seq Host Starttime Runtime Send Receive Exitval Signal Command 2521 1 : 1376580069.544 0.008 0 0 1 0 exit 1 2522 2 : 1376580069.552 0.009 0 0 2 0 exit 2 2523 3 : 1376580069.560 0.012 0 0 3 0 exit 3 2524 4 : 1376580069.571 0.005 0 0 0 0 exit 0 2525 2526 Seq Host Starttime Runtime Send Receive Exitval Signal Command 2527 1 : 1376580069.544 0.008 0 0 1 0 exit 1 2528 2 : 1376580069.552 0.009 0 0 2 0 exit 2 2529 3 : 1376580069.560 0.012 0 0 3 0 exit 3 2530 4 : 1376580069.571 0.005 0 0 0 0 exit 0 2531 5 : 1376580070.028 0.009 0 0 0 0 exit 0 2532 6 : 1376580070.038 0.007 0 0 0 0 exit 0 2533 2534 2535Note how the start time of the last 2 jobs is clearly different from the second run. 2536 2537With \ **--resume-failed**\ GNU \ **parallel**\ will re-run the jobs that failed: 2538 2539 2540.. code-block:: perl 2541 2542 parallel --resume-failed --joblog /tmp/log exit ::: 1 2 3 0 0 0 2543 cat /tmp/log 2544 2545 2546Output: 2547 2548 2549.. code-block:: perl 2550 2551 Seq Host Starttime Runtime Send Receive Exitval Signal Command 2552 1 : 1376580069.544 0.008 0 0 1 0 exit 1 2553 2 : 1376580069.552 0.009 0 0 2 0 exit 2 2554 3 : 1376580069.560 0.012 0 0 3 0 exit 3 2555 4 : 1376580069.571 0.005 0 0 0 0 exit 0 2556 5 : 1376580070.028 0.009 0 0 0 0 exit 0 2557 6 : 1376580070.038 0.007 0 0 0 0 exit 0 2558 1 : 1376580154.433 0.010 0 0 1 0 exit 1 2559 2 : 1376580154.444 0.022 0 0 2 0 exit 2 2560 3 : 1376580154.466 0.005 0 0 3 0 exit 3 2561 2562 2563Note how seq 1 2 3 have been repeated because they had exit value 2564different from 0. 2565 2566\ **--retry-failed**\ does almost the same as \ **--resume-failed**\ . Where 2567\ **--resume-failed**\ reads the commands from the command line (and 2568ignores the commands in the joblog), \ **--retry-failed**\ ignores the 2569command line and reruns the commands mentioned in the joblog. 2570 2571 2572.. code-block:: perl 2573 2574 parallel --retry-failed --joblog /tmp/log 2575 cat /tmp/log 2576 2577 2578Output: 2579 2580 2581.. code-block:: perl 2582 2583 Seq Host Starttime Runtime Send Receive Exitval Signal Command 2584 1 : 1376580069.544 0.008 0 0 1 0 exit 1 2585 2 : 1376580069.552 0.009 0 0 2 0 exit 2 2586 3 : 1376580069.560 0.012 0 0 3 0 exit 3 2587 4 : 1376580069.571 0.005 0 0 0 0 exit 0 2588 5 : 1376580070.028 0.009 0 0 0 0 exit 0 2589 6 : 1376580070.038 0.007 0 0 0 0 exit 0 2590 1 : 1376580154.433 0.010 0 0 1 0 exit 1 2591 2 : 1376580154.444 0.022 0 0 2 0 exit 2 2592 3 : 1376580154.466 0.005 0 0 3 0 exit 3 2593 1 : 1376580164.633 0.010 0 0 1 0 exit 1 2594 2 : 1376580164.644 0.022 0 0 2 0 exit 2 2595 3 : 1376580164.666 0.005 0 0 3 0 exit 3 2596 2597 2598 2599Termination 2600=========== 2601 2602 2603Unconditional termination 2604------------------------- 2605 2606 2607By default GNU \ **parallel**\ will wait for all jobs to finish before exiting. 2608 2609If you send GNU \ **parallel**\ the \ **TERM**\ signal, GNU \ **parallel**\ will 2610stop spawning new jobs and wait for the remaining jobs to finish. If 2611you send GNU \ **parallel**\ the \ **TERM**\ signal again, GNU \ **parallel**\ 2612will kill all running jobs and exit. 2613 2614 2615Termination dependent on job status 2616----------------------------------- 2617 2618 2619For certain jobs there is no need to continue if one of the jobs fails 2620and has an exit code different from 0. GNU \ **parallel**\ will stop spawning new jobs 2621with \ **--halt soon,fail=1**\ : 2622 2623 2624.. code-block:: perl 2625 2626 parallel -j2 --halt soon,fail=1 echo {}\; exit {} ::: 0 0 1 2 3 2627 2628 2629Output: 2630 2631 2632.. code-block:: perl 2633 2634 0 2635 0 2636 1 2637 parallel: This job failed: 2638 echo 1; exit 1 2639 parallel: Starting no more jobs. Waiting for 1 jobs to finish. 2640 2 2641 2642 2643With \ **--halt now,fail=1**\ the running jobs will be killed immediately: 2644 2645 2646.. code-block:: perl 2647 2648 parallel -j2 --halt now,fail=1 echo {}\; exit {} ::: 0 0 1 2 3 2649 2650 2651Output: 2652 2653 2654.. code-block:: perl 2655 2656 0 2657 0 2658 1 2659 parallel: This job failed: 2660 echo 1; exit 1 2661 2662 2663If \ **--halt**\ is given a percentage this percentage of the jobs must fail 2664before GNU \ **parallel**\ stops spawning more jobs: 2665 2666 2667.. code-block:: perl 2668 2669 parallel -j2 --halt soon,fail=20% echo {}\; exit {} \ 2670 ::: 0 1 2 3 4 5 6 7 8 9 2671 2672 2673Output: 2674 2675 2676.. code-block:: perl 2677 2678 0 2679 1 2680 parallel: This job failed: 2681 echo 1; exit 1 2682 2 2683 parallel: This job failed: 2684 echo 2; exit 2 2685 parallel: Starting no more jobs. Waiting for 1 jobs to finish. 2686 3 2687 parallel: This job failed: 2688 echo 3; exit 3 2689 2690 2691If you are looking for success instead of failures, you can use 2692\ **success**\ . This will finish as soon as the first job succeeds: 2693 2694 2695.. code-block:: perl 2696 2697 parallel -j2 --halt now,success=1 echo {}\; exit {} ::: 1 2 3 0 4 5 6 2698 2699 2700Output: 2701 2702 2703.. code-block:: perl 2704 2705 1 2706 2 2707 3 2708 0 2709 parallel: This job succeeded: 2710 echo 0; exit 0 2711 2712 2713GNU \ **parallel**\ can retry the command with \ **--retries**\ . This is useful if a 2714command fails for unknown reasons now and then. 2715 2716 2717.. code-block:: perl 2718 2719 parallel -k --retries 3 \ 2720 'echo tried {} >>/tmp/runs; echo completed {}; exit {}' ::: 1 2 0 2721 cat /tmp/runs 2722 2723 2724Output: 2725 2726 2727.. code-block:: perl 2728 2729 completed 1 2730 completed 2 2731 completed 0 2732 2733 tried 1 2734 tried 2 2735 tried 1 2736 tried 2 2737 tried 1 2738 tried 2 2739 tried 0 2740 2741 2742Note how job 1 and 2 were tried 3 times, but 0 was not retried because it had exit code 0. 2743 2744 2745Termination signals (advanced) 2746------------------------------ 2747 2748 2749Using \ **--termseq**\ you can control which signals are sent when killing 2750children. Normally children will be killed by sending them \ **SIGTERM**\ , 2751waiting 200 ms, then another \ **SIGTERM**\ , waiting 100 ms, then another 2752\ **SIGTERM**\ , waiting 50 ms, then a \ **SIGKILL**\ , finally waiting 25 ms 2753before giving up. It looks like this: 2754 2755 2756.. code-block:: perl 2757 2758 show_signals() { 2759 perl -e 'for(keys %SIG) { 2760 $SIG{$_} = eval "sub { print \"Got $_\\n\"; }"; 2761 } 2762 while(1){sleep 1}' 2763 } 2764 export -f show_signals 2765 echo | parallel --termseq TERM,200,TERM,100,TERM,50,KILL,25 \ 2766 -u --timeout 1 show_signals 2767 2768 2769Output: 2770 2771 2772.. code-block:: perl 2773 2774 Got TERM 2775 Got TERM 2776 Got TERM 2777 2778 2779Or just: 2780 2781 2782.. code-block:: perl 2783 2784 echo | parallel -u --timeout 1 show_signals 2785 2786 2787Output: Same as above. 2788 2789You can change this to \ **SIGINT**\ , \ **SIGTERM**\ , \ **SIGKILL**\ : 2790 2791 2792.. code-block:: perl 2793 2794 echo | parallel --termseq INT,200,TERM,100,KILL,25 \ 2795 -u --timeout 1 show_signals 2796 2797 2798Output: 2799 2800 2801.. code-block:: perl 2802 2803 Got INT 2804 Got TERM 2805 2806 2807The \ **SIGKILL**\ does not show because it cannot be caught, and thus the 2808child dies. 2809 2810 2811 2812Limiting the resources 2813====================== 2814 2815 2816To avoid overloading systems GNU \ **parallel**\ can look at the system load 2817before starting another job: 2818 2819 2820.. code-block:: perl 2821 2822 parallel --load 100% echo load is less than {} job per cpu ::: 1 2823 2824 2825Output: 2826 2827 2828.. code-block:: perl 2829 2830 [when then load is less than the number of cpu cores] 2831 load is less than 1 job per cpu 2832 2833 2834GNU \ **parallel**\ can also check if the system is swapping. 2835 2836 2837.. code-block:: perl 2838 2839 parallel --noswap echo the system is not swapping ::: now 2840 2841 2842Output: 2843 2844 2845.. code-block:: perl 2846 2847 [when then system is not swapping] 2848 the system is not swapping now 2849 2850 2851Some jobs need a lot of memory, and should only be started when there 2852is enough memory free. Using \ **--memfree**\ GNU \ **parallel**\ can check if 2853there is enough memory free. Additionally, GNU \ **parallel**\ will kill 2854off the youngest job if the memory free falls below 50% of the 2855size. The killed job will put back on the queue and retried later. 2856 2857 2858.. code-block:: perl 2859 2860 parallel --memfree 1G echo will run if more than 1 GB is ::: free 2861 2862 2863GNU \ **parallel**\ can run the jobs with a nice value. This will work both 2864locally and remotely. 2865 2866 2867.. code-block:: perl 2868 2869 parallel --nice 17 echo this is being run with nice -n ::: 17 2870 2871 2872Output: 2873 2874 2875.. code-block:: perl 2876 2877 this is being run with nice -n 17 2878 2879 2880 2881 2882**************** 2883Remote execution 2884**************** 2885 2886 2887GNU \ **parallel**\ can run jobs on remote servers. It uses \ **ssh**\ to 2888communicate with the remote machines. 2889 2890Sshlogin 2891======== 2892 2893 2894The most basic sshlogin is \ **-S**\ \ *host*\ : 2895 2896 2897.. code-block:: perl 2898 2899 parallel -S $SERVER1 echo running on ::: $SERVER1 2900 2901 2902Output: 2903 2904 2905.. code-block:: perl 2906 2907 running on [$SERVER1] 2908 2909 2910To use a different username prepend the server with \ *username@*\ : 2911 2912 2913.. code-block:: perl 2914 2915 parallel -S username@$SERVER1 echo running on ::: username@$SERVER1 2916 2917 2918Output: 2919 2920 2921.. code-block:: perl 2922 2923 running on [username@$SERVER1] 2924 2925 2926The special sshlogin \ **:**\ is the local machine: 2927 2928 2929.. code-block:: perl 2930 2931 parallel -S : echo running on ::: the_local_machine 2932 2933 2934Output: 2935 2936 2937.. code-block:: perl 2938 2939 running on the_local_machine 2940 2941 2942If \ **ssh**\ is not in $PATH it can be prepended to $SERVER1: 2943 2944 2945.. code-block:: perl 2946 2947 parallel -S '/usr/bin/ssh '$SERVER1 echo custom ::: ssh 2948 2949 2950Output: 2951 2952 2953.. code-block:: perl 2954 2955 custom ssh 2956 2957 2958The \ **ssh**\ command can also be given using \ **--ssh**\ : 2959 2960 2961.. code-block:: perl 2962 2963 parallel --ssh /usr/bin/ssh -S $SERVER1 echo custom ::: ssh 2964 2965 2966or by setting \ **$PARALLEL_SSH**\ : 2967 2968 2969.. code-block:: perl 2970 2971 export PARALLEL_SSH=/usr/bin/ssh 2972 parallel -S $SERVER1 echo custom ::: ssh 2973 2974 2975Several servers can be given using multiple \ **-S**\ : 2976 2977 2978.. code-block:: perl 2979 2980 parallel -S $SERVER1 -S $SERVER2 echo ::: running on more hosts 2981 2982 2983Output (the order may be different): 2984 2985 2986.. code-block:: perl 2987 2988 running 2989 on 2990 more 2991 hosts 2992 2993 2994Or they can be separated by \ **,**\ : 2995 2996 2997.. code-block:: perl 2998 2999 parallel -S $SERVER1,$SERVER2 echo ::: running on more hosts 3000 3001 3002Output: Same as above. 3003 3004Or newline: 3005 3006 3007.. code-block:: perl 3008 3009 # This gives a \n between $SERVER1 and $SERVER2 3010 SERVERS="`echo $SERVER1; echo $SERVER2`" 3011 parallel -S "$SERVERS" echo ::: running on more hosts 3012 3013 3014They can also be read from a file (replace \ *user@*\ with the user on \ **$SERVER2**\ ): 3015 3016 3017.. code-block:: perl 3018 3019 echo $SERVER1 > nodefile 3020 # Force 4 cores, special ssh-command, username 3021 echo 4//usr/bin/ssh user@$SERVER2 >> nodefile 3022 parallel --sshloginfile nodefile echo ::: running on more hosts 3023 3024 3025Output: Same as above. 3026 3027Every time a job finished, the \ **--sshloginfile**\ will be re-read, so 3028it is possible to both add and remove hosts while running. 3029 3030The special \ **--sshloginfile ..**\ reads from \ **~/.parallel/sshloginfile**\ . 3031 3032To force GNU \ **parallel**\ to treat a server having a given number of CPU 3033cores prepend the number of core followed by \ **/**\ to the sshlogin: 3034 3035 3036.. code-block:: perl 3037 3038 parallel -S 4/$SERVER1 echo force {} cpus on server ::: 4 3039 3040 3041Output: 3042 3043 3044.. code-block:: perl 3045 3046 force 4 cpus on server 3047 3048 3049Servers can be put into groups by prepending \ *@groupname*\ to the 3050server and the group can then be selected by appending \ *@groupname*\ to 3051the argument if using \ **--hostgroup**\ : 3052 3053 3054.. code-block:: perl 3055 3056 parallel --hostgroup -S @grp1/$SERVER1 -S @grp2/$SERVER2 echo {} \ 3057 ::: run_on_grp1@grp1 run_on_grp2@grp2 3058 3059 3060Output: 3061 3062 3063.. code-block:: perl 3064 3065 run_on_grp1 3066 run_on_grp2 3067 3068 3069A host can be in multiple groups by separating the groups with \ **+**\ , and 3070you can force GNU \ **parallel**\ to limit the groups on which the command 3071can be run with \ **-S**\ \ *@groupname*\ : 3072 3073 3074.. code-block:: perl 3075 3076 parallel -S @grp1 -S @grp1+grp2/$SERVER1 -S @grp2/SERVER2 echo {} \ 3077 ::: run_on_grp1 also_grp1 3078 3079 3080Output: 3081 3082 3083.. code-block:: perl 3084 3085 run_on_grp1 3086 also_grp1 3087 3088 3089 3090Transferring files 3091================== 3092 3093 3094GNU \ **parallel**\ can transfer the files to be processed to the remote 3095host. It does that using rsync. 3096 3097 3098.. code-block:: perl 3099 3100 echo This is input_file > input_file 3101 parallel -S $SERVER1 --transferfile {} cat ::: input_file 3102 3103 3104Output: 3105 3106 3107.. code-block:: perl 3108 3109 This is input_file 3110 3111 3112If the files are processed into another file, the resulting file can be 3113transferred back: 3114 3115 3116.. code-block:: perl 3117 3118 echo This is input_file > input_file 3119 parallel -S $SERVER1 --transferfile {} --return {}.out \ 3120 cat {} ">"{}.out ::: input_file 3121 cat input_file.out 3122 3123 3124Output: Same as above. 3125 3126To remove the input and output file on the remote server use \ **--cleanup**\ : 3127 3128 3129.. code-block:: perl 3130 3131 echo This is input_file > input_file 3132 parallel -S $SERVER1 --transferfile {} --return {}.out --cleanup \ 3133 cat {} ">"{}.out ::: input_file 3134 cat input_file.out 3135 3136 3137Output: Same as above. 3138 3139There is a shorthand for \ **--transferfile {} --return --cleanup**\ called \ **--trc**\ : 3140 3141 3142.. code-block:: perl 3143 3144 echo This is input_file > input_file 3145 parallel -S $SERVER1 --trc {}.out cat {} ">"{}.out ::: input_file 3146 cat input_file.out 3147 3148 3149Output: Same as above. 3150 3151Some jobs need a common database for all jobs. GNU \ **parallel**\ can 3152transfer that using \ **--basefile**\ which will transfer the file before the 3153first job: 3154 3155 3156.. code-block:: perl 3157 3158 echo common data > common_file 3159 parallel --basefile common_file -S $SERVER1 \ 3160 cat common_file\; echo {} ::: foo 3161 3162 3163Output: 3164 3165 3166.. code-block:: perl 3167 3168 common data 3169 foo 3170 3171 3172To remove it from the remote host after the last job use \ **--cleanup**\ . 3173 3174 3175Working dir 3176=========== 3177 3178 3179The default working dir on the remote machines is the login dir. This 3180can be changed with \ **--workdir**\ \ *mydir*\ . 3181 3182Files transferred using \ **--transferfile**\ and \ **--return**\ will be relative 3183to \ *mydir*\ on remote computers, and the command will be executed in 3184the dir \ *mydir*\ . 3185 3186The special \ *mydir*\ value \ **...**\ will create working dirs under 3187\ **~/.parallel/tmp**\ on the remote computers. If \ **--cleanup**\ is given 3188these dirs will be removed. 3189 3190The special \ *mydir*\ value \ **.**\ uses the current working dir. If the 3191current working dir is beneath your home dir, the value \ **.**\ is 3192treated as the relative path to your home dir. This means that if your 3193home dir is different on remote computers (e.g. if your login is 3194different) the relative path will still be relative to your home dir. 3195 3196 3197.. code-block:: perl 3198 3199 parallel -S $SERVER1 pwd ::: "" 3200 parallel --workdir . -S $SERVER1 pwd ::: "" 3201 parallel --workdir ... -S $SERVER1 pwd ::: "" 3202 3203 3204Output: 3205 3206 3207.. code-block:: perl 3208 3209 [the login dir on $SERVER1] 3210 [current dir relative on $SERVER1] 3211 [a dir in ~/.parallel/tmp/...] 3212 3213 3214 3215Avoid overloading sshd 3216====================== 3217 3218 3219If many jobs are started on the same server, \ **sshd**\ can be 3220overloaded. GNU \ **parallel**\ can insert a delay between each job run on 3221the same server: 3222 3223 3224.. code-block:: perl 3225 3226 parallel -S $SERVER1 --sshdelay 0.2 echo ::: 1 2 3 3227 3228 3229Output (the order may be different): 3230 3231 3232.. code-block:: perl 3233 3234 1 3235 2 3236 3 3237 3238 3239\ **sshd**\ will be less overloaded if using \ **--controlmaster**\ , which will 3240multiplex ssh connections: 3241 3242 3243.. code-block:: perl 3244 3245 parallel --controlmaster -S $SERVER1 echo ::: 1 2 3 3246 3247 3248Output: Same as above. 3249 3250 3251Ignore hosts that are down 3252========================== 3253 3254 3255In clusters with many hosts a few of them are often down. GNU \ **parallel**\ 3256can ignore those hosts. In this case the host 173.194.32.46 is down: 3257 3258 3259.. code-block:: perl 3260 3261 parallel --filter-hosts -S 173.194.32.46,$SERVER1 echo ::: bar 3262 3263 3264Output: 3265 3266 3267.. code-block:: perl 3268 3269 bar 3270 3271 3272 3273Running the same commands on all hosts 3274====================================== 3275 3276 3277GNU \ **parallel**\ can run the same command on all the hosts: 3278 3279 3280.. code-block:: perl 3281 3282 parallel --onall -S $SERVER1,$SERVER2 echo ::: foo bar 3283 3284 3285Output (the order may be different): 3286 3287 3288.. code-block:: perl 3289 3290 foo 3291 bar 3292 foo 3293 bar 3294 3295 3296Often you will just want to run a single command on all hosts with out 3297arguments. \ **--nonall**\ is a no argument \ **--onall**\ : 3298 3299 3300.. code-block:: perl 3301 3302 parallel --nonall -S $SERVER1,$SERVER2 echo foo bar 3303 3304 3305Output: 3306 3307 3308.. code-block:: perl 3309 3310 foo bar 3311 foo bar 3312 3313 3314When \ **--tag**\ is used with \ **--nonall**\ and \ **--onall**\ the \ **--tagstring**\ is the host: 3315 3316 3317.. code-block:: perl 3318 3319 parallel --nonall --tag -S $SERVER1,$SERVER2 echo foo bar 3320 3321 3322Output (the order may be different): 3323 3324 3325.. code-block:: perl 3326 3327 $SERVER1 foo bar 3328 $SERVER2 foo bar 3329 3330 3331\ **--jobs**\ sets the number of servers to log in to in parallel. 3332 3333 3334Transferring environment variables and functions 3335================================================ 3336 3337 3338\ **env_parallel**\ is a shell function that transfers all aliases, 3339functions, variables, and arrays. You active it by running: 3340 3341 3342.. code-block:: perl 3343 3344 source `which env_parallel.bash` 3345 3346 3347Replace \ **bash**\ with the shell you use. 3348 3349Now you can use \ **env_parallel**\ instead of \ **parallel**\ and still have 3350your environment: 3351 3352 3353.. code-block:: perl 3354 3355 alias myecho=echo 3356 myvar="Joe's var is" 3357 env_parallel -S $SERVER1 'myecho $myvar' ::: green 3358 3359 3360Output: 3361 3362 3363.. code-block:: perl 3364 3365 Joe's var is green 3366 3367 3368The disadvantage is that if your environment is huge \ **env_parallel**\ 3369will fail. 3370 3371When \ **env_parallel**\ fails, you can still use \ **--env**\ to tell GNU 3372\ **parallel**\ to transfer an environment variable to the remote system. 3373 3374 3375.. code-block:: perl 3376 3377 MYVAR='foo bar' 3378 export MYVAR 3379 parallel --env MYVAR -S $SERVER1 echo '$MYVAR' ::: baz 3380 3381 3382Output: 3383 3384 3385.. code-block:: perl 3386 3387 foo bar baz 3388 3389 3390This works for functions, too, if your shell is Bash: 3391 3392 3393.. code-block:: perl 3394 3395 # This only works in Bash 3396 my_func() { 3397 echo in my_func $1 3398 } 3399 export -f my_func 3400 parallel --env my_func -S $SERVER1 my_func ::: baz 3401 3402 3403Output: 3404 3405 3406.. code-block:: perl 3407 3408 in my_func baz 3409 3410 3411GNU \ **parallel**\ can copy all user defined variables and functions to 3412the remote system. It just needs to record which ones to ignore in 3413\ **~/.parallel/ignored_vars**\ . Do that by running this once: 3414 3415 3416.. code-block:: perl 3417 3418 parallel --record-env 3419 cat ~/.parallel/ignored_vars 3420 3421 3422Output: 3423 3424 3425.. code-block:: perl 3426 3427 [list of variables to ignore - including $PATH and $HOME] 3428 3429 3430Now all other variables and functions defined will be copied when 3431using \ **--env _**\ . 3432 3433 3434.. code-block:: perl 3435 3436 # The function is only copied if using Bash 3437 my_func2() { 3438 echo in my_func2 $VAR $1 3439 } 3440 export -f my_func2 3441 VAR=foo 3442 export VAR 3443 3444 parallel --env _ -S $SERVER1 'echo $VAR; my_func2' ::: bar 3445 3446 3447Output: 3448 3449 3450.. code-block:: perl 3451 3452 foo 3453 in my_func2 foo bar 3454 3455 3456If you use \ **env_parallel**\ the variables, functions, and aliases do 3457not even need to be exported to be copied: 3458 3459 3460.. code-block:: perl 3461 3462 NOT='not exported var' 3463 alias myecho=echo 3464 not_ex() { 3465 myecho in not_exported_func $NOT $1 3466 } 3467 env_parallel --env _ -S $SERVER1 'echo $NOT; not_ex' ::: bar 3468 3469 3470Output: 3471 3472 3473.. code-block:: perl 3474 3475 not exported var 3476 in not_exported_func not exported var bar 3477 3478 3479 3480Showing what is actually run 3481============================ 3482 3483 3484\ **--verbose**\ will show the command that would be run on the local 3485machine. 3486 3487When using \ **--cat**\ , \ **--pipepart**\ , or when a job is run on a remote 3488machine, the command is wrapped with helper scripts. \ **-vv**\ shows all 3489of this. 3490 3491 3492.. code-block:: perl 3493 3494 parallel -vv --pipepart --block 1M wc :::: num30000 3495 3496 3497Output: 3498 3499 3500.. code-block:: perl 3501 3502 <num30000 perl -e 'while(@ARGV) { sysseek(STDIN,shift,0) || die; 3503 $left = shift; while($read = sysread(STDIN,$buf, ($left > 131072 3504 ? 131072 : $left))){ $left -= $read; syswrite(STDOUT,$buf); } }' 3505 0 0 0 168894 | (wc) 3506 30000 30000 168894 3507 3508 3509When the command gets more complex, the output is so hard to read, 3510that it is only useful for debugging: 3511 3512 3513.. code-block:: perl 3514 3515 my_func3() { 3516 echo in my_func $1 > $1.out 3517 } 3518 export -f my_func3 3519 parallel -vv --workdir ... --nice 17 --env _ --trc {}.out \ 3520 -S $SERVER1 my_func3 {} ::: abc-file 3521 3522 3523Output will be similar to: 3524 3525 3526.. code-block:: perl 3527 3528 ( ssh server -- mkdir -p ./.parallel/tmp/aspire-1928520-1;rsync 3529 --protocol 30 -rlDzR -essh ./abc-file 3530 server:./.parallel/tmp/aspire-1928520-1 );ssh server -- exec perl -e 3531 \''@GNU_Parallel=("use","IPC::Open3;","use","MIME::Base64"); 3532 eval"@GNU_Parallel";my$eval=decode_base64(join"",@ARGV);eval$eval;'\' 3533 c3lzdGVtKCJta2RpciIsIi1wIiwiLS0iLCIucGFyYWxsZWwvdG1wL2FzcGlyZS0xOTI4N 3534 TsgY2hkaXIgIi5wYXJhbGxlbC90bXAvYXNwaXJlLTE5Mjg1MjAtMSIgfHxwcmludChTVE 3535 BhcmFsbGVsOiBDYW5ub3QgY2hkaXIgdG8gLnBhcmFsbGVsL3RtcC9hc3BpcmUtMTkyODU 3536 iKSAmJiBleGl0IDI1NTskRU5WeyJPTERQV0QifT0iL2hvbWUvdGFuZ2UvcHJpdmF0L3Bh 3537 IjskRU5WeyJQQVJBTExFTF9QSUQifT0iMTkyODUyMCI7JEVOVnsiUEFSQUxMRUxfU0VRI 3538 0BiYXNoX2Z1bmN0aW9ucz1xdyhteV9mdW5jMyk7IGlmKCRFTlZ7IlNIRUxMIn09fi9jc2 3539 ByaW50IFNUREVSUiAiQ1NIL1RDU0ggRE8gTk9UIFNVUFBPUlQgbmV3bGluZXMgSU4gVkF 3540 TL0ZVTkNUSU9OUy4gVW5zZXQgQGJhc2hfZnVuY3Rpb25zXG4iOyBleGVjICJmYWxzZSI7 3541 YXNoZnVuYyA9ICJteV9mdW5jMygpIHsgIGVjaG8gaW4gbXlfZnVuYyBcJDEgPiBcJDEub 3542 Xhwb3J0IC1mIG15X2Z1bmMzID4vZGV2L251bGw7IjtAQVJHVj0ibXlfZnVuYzMgYWJjLW 3543 RzaGVsbD0iJEVOVntTSEVMTH0iOyR0bXBkaXI9Ii90bXAiOyRuaWNlPTE3O2RveyRFTlZ 3544 MRUxfVE1QfT0kdG1wZGlyLiIvcGFyIi5qb2luIiIsbWFweygwLi45LCJhIi4uInoiLCJB 3545 KVtyYW5kKDYyKV19KDEuLjUpO313aGlsZSgtZSRFTlZ7UEFSQUxMRUxfVE1QfSk7JFNJ 3546 fT1zdWJ7JGRvbmU9MTt9OyRwaWQ9Zm9yazt1bmxlc3MoJHBpZCl7c2V0cGdycDtldmFse 3547 W9yaXR5KDAsMCwkbmljZSl9O2V4ZWMkc2hlbGwsIi1jIiwoJGJhc2hmdW5jLiJAQVJHVi 3548 JleGVjOiQhXG4iO31kb3skcz0kczwxPzAuMDAxKyRzKjEuMDM6JHM7c2VsZWN0KHVuZGV 3549 mLHVuZGVmLCRzKTt9dW50aWwoJGRvbmV8fGdldHBwaWQ9PTEpO2tpbGwoU0lHSFVQLC0k 3550 dW5sZXNzJGRvbmU7d2FpdDtleGl0KCQ/JjEyNz8xMjgrKCQ/JjEyNyk6MSskPz4+OCk=; 3551 _EXIT_status=$?; mkdir -p ./.; rsync --protocol 30 --rsync-path=cd\ 3552 ./.parallel/tmp/aspire-1928520-1/./.\;\ rsync -rlDzR -essh 3553 server:./abc-file.out ./.;ssh server -- \(rm\ -f\ 3554 ./.parallel/tmp/aspire-1928520-1/abc-file\;\ sh\ -c\ \'rmdir\ 3555 ./.parallel/tmp/aspire-1928520-1/\ ./.parallel/tmp/\ ./.parallel/\ 3556 2\>/dev/null\'\;rm\ -rf\ ./.parallel/tmp/aspire-1928520-1\;\);ssh 3557 server -- \(rm\ -f\ ./.parallel/tmp/aspire-1928520-1/abc-file.out\;\ 3558 sh\ -c\ \'rmdir\ ./.parallel/tmp/aspire-1928520-1/\ ./.parallel/tmp/\ 3559 ./.parallel/\ 2\>/dev/null\'\;rm\ -rf\ 3560 ./.parallel/tmp/aspire-1928520-1\;\);ssh server -- rm -rf 3561 .parallel/tmp/aspire-1928520-1; exit $_EXIT_status; 3562 3563 3564 3565 3566******************************************* 3567Saving output to shell variables (advanced) 3568******************************************* 3569 3570 3571GNU \ **parset**\ will set shell variables to the output of GNU 3572\ **parallel**\ . GNU \ **parset**\ has one important limitation: It cannot be 3573part of a pipe. In particular this means it cannot read anything from 3574standard input (stdin) or pipe output to another program. 3575 3576To use GNU \ **parset**\ prepend command with destination variables: 3577 3578 3579.. code-block:: perl 3580 3581 parset myvar1,myvar2 echo ::: a b 3582 echo $myvar1 3583 echo $myvar2 3584 3585 3586Output: 3587 3588 3589.. code-block:: perl 3590 3591 a 3592 b 3593 3594 3595If you only give a single variable, it will be treated as an array: 3596 3597 3598.. code-block:: perl 3599 3600 parset myarray seq {} 5 ::: 1 2 3 3601 echo "${myarray[1]}" 3602 3603 3604Output: 3605 3606 3607.. code-block:: perl 3608 3609 2 3610 3 3611 4 3612 5 3613 3614 3615The commands to run can be an array: 3616 3617 3618.. code-block:: perl 3619 3620 cmd=("echo '<<joe \"double space\" cartoon>>'" "pwd") 3621 parset data ::: "${cmd[@]}" 3622 echo "${data[0]}" 3623 echo "${data[1]}" 3624 3625 3626Output: 3627 3628 3629.. code-block:: perl 3630 3631 <<joe "double space" cartoon>> 3632 [current dir] 3633 3634 3635 3636******************************** 3637Saving to an SQL base (advanced) 3638******************************** 3639 3640 3641GNU \ **parallel**\ can save into an SQL base. Point GNU \ **parallel**\ to a 3642table and it will put the joblog there together with the variables and 3643the output each in their own column. 3644 3645CSV as SQL base 3646=============== 3647 3648 3649The simplest is to use a CSV file as the storage table: 3650 3651 3652.. code-block:: perl 3653 3654 parallel --sqlandworker csv:///%2Ftmp/log.csv \ 3655 seq ::: 10 ::: 12 13 14 3656 cat /tmp/log.csv 3657 3658 3659Note how '/' in the path must be written as %2F. 3660 3661Output will be similar to: 3662 3663 3664.. code-block:: perl 3665 3666 Seq,Host,Starttime,JobRuntime,Send,Receive,Exitval,_Signal, 3667 Command,V1,V2,Stdout,Stderr 3668 1,:,1458254498.254,0.069,0,9,0,0,"seq 10 12",10,12,"10 3669 11 3670 12 3671 ", 3672 2,:,1458254498.278,0.080,0,12,0,0,"seq 10 13",10,13,"10 3673 11 3674 12 3675 13 3676 ", 3677 3,:,1458254498.301,0.083,0,15,0,0,"seq 10 14",10,14,"10 3678 11 3679 12 3680 13 3681 14 3682 ", 3683 3684 3685A proper CSV reader (like LibreOffice or R's read.csv) will read this 3686format correctly - even with fields containing newlines as above. 3687 3688If the output is big you may want to put it into files using \ **--results**\ : 3689 3690 3691.. code-block:: perl 3692 3693 parallel --results outdir --sqlandworker csv:///%2Ftmp/log2.csv \ 3694 seq ::: 10 ::: 12 13 14 3695 cat /tmp/log2.csv 3696 3697 3698Output will be similar to: 3699 3700 3701.. code-block:: perl 3702 3703 Seq,Host,Starttime,JobRuntime,Send,Receive,Exitval,_Signal, 3704 Command,V1,V2,Stdout,Stderr 3705 1,:,1458824738.287,0.029,0,9,0,0, 3706 "seq 10 12",10,12,outdir/1/10/2/12/stdout,outdir/1/10/2/12/stderr 3707 2,:,1458824738.298,0.025,0,12,0,0, 3708 "seq 10 13",10,13,outdir/1/10/2/13/stdout,outdir/1/10/2/13/stderr 3709 3,:,1458824738.309,0.026,0,15,0,0, 3710 "seq 10 14",10,14,outdir/1/10/2/14/stdout,outdir/1/10/2/14/stderr 3711 3712 3713 3714DBURL as table 3715============== 3716 3717 3718The CSV file is an example of a DBURL. 3719 3720GNU \ **parallel**\ uses a DBURL to address the table. A DBURL has this format: 3721 3722 3723.. code-block:: perl 3724 3725 vendor://[[user][:password]@][host][:port]/[database[/table] 3726 3727 3728Example: 3729 3730 3731.. code-block:: perl 3732 3733 mysql://scott:tiger@my.example.com/mydatabase/mytable 3734 postgresql://scott:tiger@pg.example.com/mydatabase/mytable 3735 sqlite3:///%2Ftmp%2Fmydatabase/mytable 3736 csv:///%2Ftmp/log.csv 3737 3738 3739To refer to \ **/tmp/mydatabase**\ with \ **sqlite**\ or \ **csv**\ you need to 3740encode the \ **/**\ as \ **%2F**\ . 3741 3742Run a job using \ **sqlite**\ on \ **mytable**\ in \ **/tmp/mydatabase**\ : 3743 3744 3745.. code-block:: perl 3746 3747 DBURL=sqlite3:///%2Ftmp%2Fmydatabase 3748 DBURLTABLE=$DBURL/mytable 3749 parallel --sqlandworker $DBURLTABLE echo ::: foo bar ::: baz quuz 3750 3751 3752To see the result: 3753 3754 3755.. code-block:: perl 3756 3757 sql $DBURL 'SELECT * FROM mytable ORDER BY Seq;' 3758 3759 3760Output will be similar to: 3761 3762 3763.. code-block:: perl 3764 3765 Seq|Host|Starttime|JobRuntime|Send|Receive|Exitval|_Signal| 3766 Command|V1|V2|Stdout|Stderr 3767 1|:|1451619638.903|0.806||8|0|0|echo foo baz|foo|baz|foo baz 3768 | 3769 2|:|1451619639.265|1.54||9|0|0|echo foo quuz|foo|quuz|foo quuz 3770 | 3771 3|:|1451619640.378|1.43||8|0|0|echo bar baz|bar|baz|bar baz 3772 | 3773 4|:|1451619641.473|0.958||9|0|0|echo bar quuz|bar|quuz|bar quuz 3774 | 3775 3776 3777The first columns are well known from \ **--joblog**\ . \ **V1**\ and \ **V2**\ are 3778data from the input sources. \ **Stdout**\ and \ **Stderr**\ are standard 3779output and standard error, respectively. 3780 3781 3782Using multiple workers 3783====================== 3784 3785 3786Using an SQL base as storage costs overhead in the order of 1 second 3787per job. 3788 3789One of the situations where it makes sense is if you have multiple 3790workers. 3791 3792You can then have a single master machine that submits jobs to the SQL 3793base (but does not do any of the work): 3794 3795 3796.. code-block:: perl 3797 3798 parallel --sqlmaster $DBURLTABLE echo ::: foo bar ::: baz quuz 3799 3800 3801On the worker machines you run exactly the same command except you 3802replace \ **--sqlmaster**\ with \ **--sqlworker**\ . 3803 3804 3805.. code-block:: perl 3806 3807 parallel --sqlworker $DBURLTABLE echo ::: foo bar ::: baz quuz 3808 3809 3810To run a master and a worker on the same machine use \ **--sqlandworker**\ 3811as shown earlier. 3812 3813 3814 3815****** 3816--pipe 3817****** 3818 3819 3820The \ **--pipe**\ functionality puts GNU \ **parallel**\ in a different mode: 3821Instead of treating the data on stdin (standard input) as arguments 3822for a command to run, the data will be sent to stdin (standard input) 3823of the command. 3824 3825The typical situation is: 3826 3827 3828.. code-block:: perl 3829 3830 command_A | command_B | command_C 3831 3832 3833where command_B is slow, and you want to speed up command_B. 3834 3835Chunk size 3836========== 3837 3838 3839By default GNU \ **parallel**\ will start an instance of command_B, read a 3840chunk of 1 MB, and pass that to the instance. Then start another 3841instance, read another chunk, and pass that to the second instance. 3842 3843 3844.. code-block:: perl 3845 3846 cat num1000000 | parallel --pipe wc 3847 3848 3849Output (the order may be different): 3850 3851 3852.. code-block:: perl 3853 3854 165668 165668 1048571 3855 149797 149797 1048579 3856 149796 149796 1048572 3857 149797 149797 1048579 3858 149797 149797 1048579 3859 149796 149796 1048572 3860 85349 85349 597444 3861 3862 3863The size of the chunk is not exactly 1 MB because GNU \ **parallel**\ only 3864passes full lines - never half a line, thus the blocksize is only 38651 MB on average. You can change the block size to 2 MB with \ **--block**\ : 3866 3867 3868.. code-block:: perl 3869 3870 cat num1000000 | parallel --pipe --block 2M wc 3871 3872 3873Output (the order may be different): 3874 3875 3876.. code-block:: perl 3877 3878 315465 315465 2097150 3879 299593 299593 2097151 3880 299593 299593 2097151 3881 85349 85349 597444 3882 3883 3884GNU \ **parallel**\ treats each line as a record. If the order of records 3885is unimportant (e.g. you need all lines processed, but you do not care 3886which is processed first), then you can use \ **--roundrobin**\ . Without 3887\ **--roundrobin**\ GNU \ **parallel**\ will start a command per block; with 3888\ **--roundrobin**\ only the requested number of jobs will be started 3889(\ **--jobs**\ ). The records will then be distributed between the running 3890jobs: 3891 3892 3893.. code-block:: perl 3894 3895 cat num1000000 | parallel --pipe -j4 --roundrobin wc 3896 3897 3898Output will be similar to: 3899 3900 3901.. code-block:: perl 3902 3903 149797 149797 1048579 3904 299593 299593 2097151 3905 315465 315465 2097150 3906 235145 235145 1646016 3907 3908 3909One of the 4 instances got a single record, 2 instances got 2 full 3910records each, and one instance got 1 full and 1 partial record. 3911 3912 3913Records 3914======= 3915 3916 3917GNU \ **parallel**\ sees the input as records. The default record is a single 3918line. 3919 3920Using \ **-N140000**\ GNU \ **parallel**\ will read 140000 records at a time: 3921 3922 3923.. code-block:: perl 3924 3925 cat num1000000 | parallel --pipe -N140000 wc 3926 3927 3928Output (the order may be different): 3929 3930 3931.. code-block:: perl 3932 3933 140000 140000 868895 3934 140000 140000 980000 3935 140000 140000 980000 3936 140000 140000 980000 3937 140000 140000 980000 3938 140000 140000 980000 3939 140000 140000 980000 3940 20000 20000 140001 3941 3942 3943Note how that the last job could not get the full 140000 lines, but 3944only 20000 lines. 3945 3946If a record is 75 lines \ **-L**\ can be used: 3947 3948 3949.. code-block:: perl 3950 3951 cat num1000000 | parallel --pipe -L75 wc 3952 3953 3954Output (the order may be different): 3955 3956 3957.. code-block:: perl 3958 3959 165600 165600 1048095 3960 149850 149850 1048950 3961 149775 149775 1048425 3962 149775 149775 1048425 3963 149850 149850 1048950 3964 149775 149775 1048425 3965 85350 85350 597450 3966 25 25 176 3967 3968 3969Note how GNU \ **parallel**\ still reads a block of around 1 MB; but 3970instead of passing full lines to \ **wc**\ it passes full 75 lines at a 3971time. This of course does not hold for the last job (which in this 3972case got 25 lines). 3973 3974 3975Fixed length records 3976==================== 3977 3978 3979Fixed length records can be processed by setting \ **--recend ''**\ and 3980\ **--block \ \*recordsize\*\ **\ . A header of size \ *n*\ can be processed with 3981\ **--header .{\ \*n\*\ }**\ . 3982 3983Here is how to process a file with a 4-byte header and a 3-byte record 3984size: 3985 3986 3987.. code-block:: perl 3988 3989 cat fixedlen | parallel --pipe --header .{4} --block 3 --recend '' \ 3990 'echo start; cat; echo' 3991 3992 3993Output: 3994 3995 3996.. code-block:: perl 3997 3998 start 3999 HHHHAAA 4000 start 4001 HHHHCCC 4002 start 4003 HHHHBBB 4004 4005 4006It may be more efficient to increase \ **--block**\ to a multiplum of the 4007record size. 4008 4009 4010Record separators 4011================= 4012 4013 4014GNU \ **parallel**\ uses separators to determine where two records split. 4015 4016\ **--recstart**\ gives the string that starts a record; \ **--recend**\ gives the 4017string that ends a record. The default is \ **--recend '\n'**\ (newline). 4018 4019If both \ **--recend**\ and \ **--recstart**\ are given, then the record will only 4020split if the recend string is immediately followed by the recstart 4021string. 4022 4023Here the \ **--recend**\ is set to \ **', '**\ : 4024 4025 4026.. code-block:: perl 4027 4028 echo /foo, bar/, /baz, qux/, | \ 4029 parallel -kN1 --recend ', ' --pipe echo JOB{#}\;cat\;echo END 4030 4031 4032Output: 4033 4034 4035.. code-block:: perl 4036 4037 JOB1 4038 /foo, END 4039 JOB2 4040 bar/, END 4041 JOB3 4042 /baz, END 4043 JOB4 4044 qux/, 4045 END 4046 4047 4048Here the \ **--recstart**\ is set to \ **/**\ : 4049 4050 4051.. code-block:: perl 4052 4053 echo /foo, bar/, /baz, qux/, | \ 4054 parallel -kN1 --recstart / --pipe echo JOB{#}\;cat\;echo END 4055 4056 4057Output: 4058 4059 4060.. code-block:: perl 4061 4062 JOB1 4063 /foo, barEND 4064 JOB2 4065 /, END 4066 JOB3 4067 /baz, quxEND 4068 JOB4 4069 /, 4070 END 4071 4072 4073Here both \ **--recend**\ and \ **--recstart**\ are set: 4074 4075 4076.. code-block:: perl 4077 4078 echo /foo, bar/, /baz, qux/, | \ 4079 parallel -kN1 --recend ', ' --recstart / --pipe \ 4080 echo JOB{#}\;cat\;echo END 4081 4082 4083Output: 4084 4085 4086.. code-block:: perl 4087 4088 JOB1 4089 /foo, bar/, END 4090 JOB2 4091 /baz, qux/, 4092 END 4093 4094 4095Note the difference between setting one string and setting both strings. 4096 4097With \ **--regexp**\ the \ **--recend**\ and \ **--recstart**\ will be treated as 4098a regular expression: 4099 4100 4101.. code-block:: perl 4102 4103 echo foo,bar,_baz,__qux, | \ 4104 parallel -kN1 --regexp --recend ,_+ --pipe \ 4105 echo JOB{#}\;cat\;echo END 4106 4107 4108Output: 4109 4110 4111.. code-block:: perl 4112 4113 JOB1 4114 foo,bar,_END 4115 JOB2 4116 baz,__END 4117 JOB3 4118 qux, 4119 END 4120 4121 4122GNU \ **parallel**\ can remove the record separators with 4123\ **--remove-rec-sep**\ /\ **--rrs**\ : 4124 4125 4126.. code-block:: perl 4127 4128 echo foo,bar,_baz,__qux, | \ 4129 parallel -kN1 --rrs --regexp --recend ,_+ --pipe \ 4130 echo JOB{#}\;cat\;echo END 4131 4132 4133Output: 4134 4135 4136.. code-block:: perl 4137 4138 JOB1 4139 foo,barEND 4140 JOB2 4141 bazEND 4142 JOB3 4143 qux, 4144 END 4145 4146 4147 4148Header 4149====== 4150 4151 4152If the input data has a header, the header can be repeated for each 4153job by matching the header with \ **--header**\ . If headers start with 4154\ **%**\ you can do this: 4155 4156 4157.. code-block:: perl 4158 4159 cat num_%header | \ 4160 parallel --header '(%.*\n)*' --pipe -N3 echo JOB{#}\;cat 4161 4162 4163Output (the order may be different): 4164 4165 4166.. code-block:: perl 4167 4168 JOB1 4169 %head1 4170 %head2 4171 1 4172 2 4173 3 4174 JOB2 4175 %head1 4176 %head2 4177 4 4178 5 4179 6 4180 JOB3 4181 %head1 4182 %head2 4183 7 4184 8 4185 9 4186 JOB4 4187 %head1 4188 %head2 4189 10 4190 4191 4192If the header is 2 lines, \ **--header**\ 2 will work: 4193 4194 4195.. code-block:: perl 4196 4197 cat num_%header | parallel --header 2 --pipe -N3 echo JOB{#}\;cat 4198 4199 4200Output: Same as above. 4201 4202 4203--pipepart 4204========== 4205 4206 4207\ **--pipe**\ is not very efficient. It maxes out at around 500 4208MB/s. \ **--pipepart**\ can easily deliver 5 GB/s. But there are a few 4209limitations. The input has to be a normal file (not a pipe) given by 4210\ **-a**\ or \ **::::**\ and \ **-L**\ /\ **-l**\ /\ **-N**\ do not work. \ **--recend**\ and 4211\ **--recstart**\ , however, \ *do*\ work, and records can often be split on 4212that alone. 4213 4214 4215.. code-block:: perl 4216 4217 parallel --pipepart -a num1000000 --block 3m wc 4218 4219 4220Output (the order may be different): 4221 4222 4223.. code-block:: perl 4224 4225 444443 444444 3000002 4226 428572 428572 3000004 4227 126985 126984 888890 4228 4229 4230 4231 4232******* 4233Shebang 4234******* 4235 4236 4237Input data and parallel command in the same file 4238================================================ 4239 4240 4241GNU \ **parallel**\ is often called as this: 4242 4243 4244.. code-block:: perl 4245 4246 cat input_file | parallel command 4247 4248 4249With \ **--shebang**\ the \ *input_file*\ and \ **parallel**\ can be combined into the same script. 4250 4251UNIX shell scripts start with a shebang line like this: 4252 4253 4254.. code-block:: perl 4255 4256 #!/bin/bash 4257 4258 4259GNU \ **parallel**\ can do that, too. With \ **--shebang**\ the arguments can be 4260listed in the file. The \ **parallel**\ command is the first line of the 4261script: 4262 4263 4264.. code-block:: perl 4265 4266 #!/usr/bin/parallel --shebang -r echo 4267 4268 foo 4269 bar 4270 baz 4271 4272 4273Output (the order may be different): 4274 4275 4276.. code-block:: perl 4277 4278 foo 4279 bar 4280 baz 4281 4282 4283 4284Parallelizing existing scripts 4285============================== 4286 4287 4288GNU \ **parallel**\ is often called as this: 4289 4290 4291.. code-block:: perl 4292 4293 cat input_file | parallel command 4294 parallel command ::: foo bar 4295 4296 4297If \ **command**\ is a script, \ **parallel**\ can be combined into a single 4298file so this will run the script in parallel: 4299 4300 4301.. code-block:: perl 4302 4303 cat input_file | command 4304 command foo bar 4305 4306 4307This \ **perl**\ script \ **perl_echo**\ works like \ **echo**\ : 4308 4309 4310.. code-block:: perl 4311 4312 #!/usr/bin/perl 4313 4314 print "@ARGV\n" 4315 4316 4317It can be called as this: 4318 4319 4320.. code-block:: perl 4321 4322 parallel perl_echo ::: foo bar 4323 4324 4325By changing the \ **#!**\ -line it can be run in parallel: 4326 4327 4328.. code-block:: perl 4329 4330 #!/usr/bin/parallel --shebang-wrap /usr/bin/perl 4331 4332 print "@ARGV\n" 4333 4334 4335Thus this will work: 4336 4337 4338.. code-block:: perl 4339 4340 perl_echo foo bar 4341 4342 4343Output (the order may be different): 4344 4345 4346.. code-block:: perl 4347 4348 foo 4349 bar 4350 4351 4352This technique can be used for: 4353 4354 4355- Perl: 4356 4357 4358 .. code-block:: perl 4359 4360 #!/usr/bin/parallel --shebang-wrap /usr/bin/perl 4361 4362 print "Arguments @ARGV\n"; 4363 4364 4365 4366 4367- Python: 4368 4369 4370 .. code-block:: perl 4371 4372 #!/usr/bin/parallel --shebang-wrap /usr/bin/python 4373 4374 import sys 4375 print 'Arguments', str(sys.argv) 4376 4377 4378 4379 4380- Bash/sh/zsh/Korn shell: 4381 4382 4383 .. code-block:: perl 4384 4385 #!/usr/bin/parallel --shebang-wrap /bin/bash 4386 4387 echo Arguments "$@" 4388 4389 4390 4391 4392- csh: 4393 4394 4395 .. code-block:: perl 4396 4397 #!/usr/bin/parallel --shebang-wrap /bin/csh 4398 4399 echo Arguments "$argv" 4400 4401 4402 4403 4404- Tcl: 4405 4406 4407 .. code-block:: perl 4408 4409 #!/usr/bin/parallel --shebang-wrap /usr/bin/tclsh 4410 4411 puts "Arguments $argv" 4412 4413 4414 4415 4416- R: 4417 4418 4419 .. code-block:: perl 4420 4421 #!/usr/bin/parallel --shebang-wrap /usr/bin/Rscript --vanilla --slave 4422 4423 args <- commandArgs(trailingOnly = TRUE) 4424 print(paste("Arguments ",args)) 4425 4426 4427 4428 4429- GNUplot: 4430 4431 4432 .. code-block:: perl 4433 4434 #!/usr/bin/parallel --shebang-wrap ARG={} /usr/bin/gnuplot 4435 4436 print "Arguments ", system('echo $ARG') 4437 4438 4439 4440 4441- Ruby: 4442 4443 4444 .. code-block:: perl 4445 4446 #!/usr/bin/parallel --shebang-wrap /usr/bin/ruby 4447 4448 print "Arguments " 4449 puts ARGV 4450 4451 4452 4453 4454- Octave: 4455 4456 4457 .. code-block:: perl 4458 4459 #!/usr/bin/parallel --shebang-wrap /usr/bin/octave 4460 4461 printf ("Arguments"); 4462 arg_list = argv (); 4463 for i = 1:nargin 4464 printf (" %s", arg_list{i}); 4465 endfor 4466 printf ("\n"); 4467 4468 4469 4470 4471- Common LISP: 4472 4473 4474 .. code-block:: perl 4475 4476 #!/usr/bin/parallel --shebang-wrap /usr/bin/clisp 4477 4478 (format t "~&~S~&" 'Arguments) 4479 (format t "~&~S~&" *args*) 4480 4481 4482 4483 4484- PHP: 4485 4486 4487 .. code-block:: perl 4488 4489 #!/usr/bin/parallel --shebang-wrap /usr/bin/php 4490 <?php 4491 echo "Arguments"; 4492 foreach(array_slice($argv,1) as $v) 4493 { 4494 echo " $v"; 4495 } 4496 echo "\n"; 4497 ?> 4498 4499 4500 4501 4502- Node.js: 4503 4504 4505 .. code-block:: perl 4506 4507 #!/usr/bin/parallel --shebang-wrap /usr/bin/node 4508 4509 var myArgs = process.argv.slice(2); 4510 console.log('Arguments ', myArgs); 4511 4512 4513 4514 4515- LUA: 4516 4517 4518 .. code-block:: perl 4519 4520 #!/usr/bin/parallel --shebang-wrap /usr/bin/lua 4521 4522 io.write "Arguments" 4523 for a = 1, #arg do 4524 io.write(" ") 4525 io.write(arg[a]) 4526 end 4527 print("") 4528 4529 4530 4531 4532- C#: 4533 4534 4535 .. code-block:: perl 4536 4537 #!/usr/bin/parallel --shebang-wrap ARGV={} /usr/bin/csharp 4538 4539 var argv = Environment.GetEnvironmentVariable("ARGV"); 4540 print("Arguments "+argv); 4541 4542 4543 4544 4545 4546 4547********* 4548Semaphore 4549********* 4550 4551 4552GNU \ **parallel**\ can work as a counting semaphore. This is slower and less 4553efficient than its normal mode. 4554 4555A counting semaphore is like a row of toilets. People needing a toilet 4556can use any toilet, but if there are more people than toilets, they 4557will have to wait for one of the toilets to become available. 4558 4559An alias for \ **parallel --semaphore**\ is \ **sem**\ . 4560 4561\ **sem**\ will follow a person to the toilets, wait until a toilet is 4562available, leave the person in the toilet and exit. 4563 4564\ **sem --fg**\ will follow a person to the toilets, wait until a toilet is 4565available, stay with the person in the toilet and exit when the person 4566exits. 4567 4568\ **sem --wait**\ will wait for all persons to leave the toilets. 4569 4570\ **sem**\ does not have a queue discipline, so the next person is chosen 4571randomly. 4572 4573\ **-j**\ sets the number of toilets. 4574 4575Mutex 4576===== 4577 4578 4579The default is to have only one toilet (this is called a mutex). The 4580program is started in the background and \ **sem**\ exits immediately. Use 4581\ **--wait**\ to wait for all \ **sem**\ s to finish: 4582 4583 4584.. code-block:: perl 4585 4586 sem 'sleep 1; echo The first finished' && 4587 echo The first is now running in the background && 4588 sem 'sleep 1; echo The second finished' && 4589 echo The second is now running in the background 4590 sem --wait 4591 4592 4593Output: 4594 4595 4596.. code-block:: perl 4597 4598 The first is now running in the background 4599 The first finished 4600 The second is now running in the background 4601 The second finished 4602 4603 4604The command can be run in the foreground with \ **--fg**\ , which will only 4605exit when the command completes: 4606 4607 4608.. code-block:: perl 4609 4610 sem --fg 'sleep 1; echo The first finished' && 4611 echo The first finished running in the foreground && 4612 sem --fg 'sleep 1; echo The second finished' && 4613 echo The second finished running in the foreground 4614 sem --wait 4615 4616 4617The difference between this and just running the command, is that a 4618mutex is set, so if other \ **sem**\ s were running in the background only one 4619would run at a time. 4620 4621To control which semaphore is used, use 4622\ **--semaphorename**\ /\ **--id**\ . Run this in one terminal: 4623 4624 4625.. code-block:: perl 4626 4627 sem --id my_id -u 'echo First started; sleep 10; echo First done' 4628 4629 4630and simultaneously this in another terminal: 4631 4632 4633.. code-block:: perl 4634 4635 sem --id my_id -u 'echo Second started; sleep 10; echo Second done' 4636 4637 4638Note how the second will only be started when the first has finished. 4639 4640 4641Counting semaphore 4642================== 4643 4644 4645A mutex is like having a single toilet: When it is in use everyone 4646else will have to wait. A counting semaphore is like having multiple 4647toilets: Several people can use the toilets, but when they all are in 4648use, everyone else will have to wait. 4649 4650\ **sem**\ can emulate a counting semaphore. Use \ **--jobs**\ to set the 4651number of toilets like this: 4652 4653 4654.. code-block:: perl 4655 4656 sem --jobs 3 --id my_id -u 'echo Start 1; sleep 5; echo 1 done' && 4657 sem --jobs 3 --id my_id -u 'echo Start 2; sleep 6; echo 2 done' && 4658 sem --jobs 3 --id my_id -u 'echo Start 3; sleep 7; echo 3 done' && 4659 sem --jobs 3 --id my_id -u 'echo Start 4; sleep 8; echo 4 done' && 4660 sem --wait --id my_id 4661 4662 4663Output: 4664 4665 4666.. code-block:: perl 4667 4668 Start 1 4669 Start 2 4670 Start 3 4671 1 done 4672 Start 4 4673 2 done 4674 3 done 4675 4 done 4676 4677 4678 4679Timeout 4680======= 4681 4682 4683With \ **--semaphoretimeout**\ you can force running the command anyway after 4684a period (positive number) or give up (negative number): 4685 4686 4687.. code-block:: perl 4688 4689 sem --id foo -u 'echo Slow started; sleep 5; echo Slow ended' && 4690 sem --id foo --semaphoretimeout 1 'echo Forced running after 1 sec' && 4691 sem --id foo --semaphoretimeout -2 'echo Give up after 2 secs' 4692 sem --id foo --wait 4693 4694 4695Output: 4696 4697 4698.. code-block:: perl 4699 4700 Slow started 4701 parallel: Warning: Semaphore timed out. Stealing the semaphore. 4702 Forced running after 1 sec 4703 parallel: Warning: Semaphore timed out. Exiting. 4704 Slow ended 4705 4706 4707Note how the 'Give up' was not run. 4708 4709 4710 4711************* 4712Informational 4713************* 4714 4715 4716GNU \ **parallel**\ has some options to give short information about the 4717configuration. 4718 4719\ **--help**\ will print a summary of the most important options: 4720 4721 4722.. code-block:: perl 4723 4724 parallel --help 4725 4726 4727Output: 4728 4729 4730.. code-block:: perl 4731 4732 Usage: 4733 4734 parallel [options] [command [arguments]] < list_of_arguments 4735 parallel [options] [command [arguments]] (::: arguments|:::: argfile(s))... 4736 cat ... | parallel --pipe [options] [command [arguments]] 4737 4738 -j n Run n jobs in parallel 4739 -k Keep same order 4740 -X Multiple arguments with context replace 4741 --colsep regexp Split input on regexp for positional replacements 4742 {} {.} {/} {/.} {#} {%} {= perl code =} Replacement strings 4743 {3} {3.} {3/} {3/.} {=3 perl code =} Positional replacement strings 4744 With --plus: {} = {+/}/{/} = {.}.{+.} = {+/}/{/.}.{+.} = {..}.{+..} = 4745 {+/}/{/..}.{+..} = {...}.{+...} = {+/}/{/...}.{+...} 4746 4747 -S sshlogin Example: foo@server.example.com 4748 --slf .. Use ~/.parallel/sshloginfile as the list of sshlogins 4749 --trc {}.bar Shorthand for --transfer --return {}.bar --cleanup 4750 --onall Run the given command with argument on all sshlogins 4751 --nonall Run the given command with no arguments on all sshlogins 4752 4753 --pipe Split stdin (standard input) to multiple jobs. 4754 --recend str Record end separator for --pipe. 4755 --recstart str Record start separator for --pipe. 4756 4757 See 'man parallel' for details 4758 4759 Academic tradition requires you to cite works you base your article on. 4760 When using programs that use GNU Parallel to process data for publication 4761 please cite: 4762 4763 O. Tange (2011): GNU Parallel - The Command-Line Power Tool, 4764 ;login: The USENIX Magazine, February 2011:42-47. 4765 4766 This helps funding further development; AND IT WON'T COST YOU A CENT. 4767 If you pay 10000 EUR you should feel free to use GNU Parallel without citing. 4768 4769 4770When asking for help, always report the full output of this: 4771 4772 4773.. code-block:: perl 4774 4775 parallel --version 4776 4777 4778Output: 4779 4780 4781.. code-block:: perl 4782 4783 GNU parallel 20210122 4784 Copyright (C) 2007-2021 Ole Tange, http://ole.tange.dk and Free Software 4785 Foundation, Inc. 4786 License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html> 4787 This is free software: you are free to change and redistribute it. 4788 GNU parallel comes with no warranty. 4789 4790 Web site: https://www.gnu.org/software/parallel 4791 4792 When using programs that use GNU Parallel to process data for publication 4793 please cite as described in 'parallel --citation'. 4794 4795 4796In scripts \ **--minversion**\ can be used to ensure the user has at least 4797this version: 4798 4799 4800.. code-block:: perl 4801 4802 parallel --minversion 20130722 && \ 4803 echo Your version is at least 20130722. 4804 4805 4806Output: 4807 4808 4809.. code-block:: perl 4810 4811 20160322 4812 Your version is at least 20130722. 4813 4814 4815If you are using GNU \ **parallel**\ for research the BibTeX citation can be 4816generated using \ **--citation**\ : 4817 4818 4819.. code-block:: perl 4820 4821 parallel --citation 4822 4823 4824Output: 4825 4826 4827.. code-block:: perl 4828 4829 Academic tradition requires you to cite works you base your article on. 4830 When using programs that use GNU Parallel to process data for publication 4831 please cite: 4832 4833 @article{Tange2011a, 4834 title = {GNU Parallel - The Command-Line Power Tool}, 4835 author = {O. Tange}, 4836 address = {Frederiksberg, Denmark}, 4837 journal = {;login: The USENIX Magazine}, 4838 month = {Feb}, 4839 number = {1}, 4840 volume = {36}, 4841 url = {https://www.gnu.org/s/parallel}, 4842 year = {2011}, 4843 pages = {42-47}, 4844 doi = {10.5281/zenodo.16303} 4845 } 4846 4847 (Feel free to use \nocite{Tange2011a}) 4848 4849 This helps funding further development; AND IT WON'T COST YOU A CENT. 4850 If you pay 10000 EUR you should feel free to use GNU Parallel without citing. 4851 4852 If you send a copy of your published article to tange@gnu.org, it will be 4853 mentioned in the release notes of next version of GNU Parallel. 4854 4855 4856With \ **--max-line-length-allowed**\ GNU \ **parallel**\ will report the maximal 4857size of the command line: 4858 4859 4860.. code-block:: perl 4861 4862 parallel --max-line-length-allowed 4863 4864 4865Output (may vary on different systems): 4866 4867 4868.. code-block:: perl 4869 4870 131071 4871 4872 4873\ **--number-of-cpus**\ and \ **--number-of-cores**\ run system specific code to 4874determine the number of CPUs and CPU cores on the system. On 4875unsupported platforms they will return 1: 4876 4877 4878.. code-block:: perl 4879 4880 parallel --number-of-cpus 4881 parallel --number-of-cores 4882 4883 4884Output (may vary on different systems): 4885 4886 4887.. code-block:: perl 4888 4889 4 4890 64 4891 4892 4893 4894******** 4895Profiles 4896******** 4897 4898 4899The defaults for GNU \ **parallel**\ can be changed systemwide by putting the 4900command line options in \ **/etc/parallel/config**\ . They can be changed for 4901a user by putting them in \ **~/.parallel/config**\ . 4902 4903Profiles work the same way, but have to be referred to with \ **--profile**\ : 4904 4905 4906.. code-block:: perl 4907 4908 echo '--nice 17' > ~/.parallel/nicetimeout 4909 echo '--timeout 300%' >> ~/.parallel/nicetimeout 4910 parallel --profile nicetimeout echo ::: A B C 4911 4912 4913Output: 4914 4915 4916.. code-block:: perl 4917 4918 A 4919 B 4920 C 4921 4922 4923Profiles can be combined: 4924 4925 4926.. code-block:: perl 4927 4928 echo '-vv --dry-run' > ~/.parallel/dryverbose 4929 parallel --profile dryverbose --profile nicetimeout echo ::: A B C 4930 4931 4932Output: 4933 4934 4935.. code-block:: perl 4936 4937 echo A 4938 echo B 4939 echo C 4940 4941 4942 4943*************** 4944Spread the word 4945*************** 4946 4947 4948I hope you have learned something from this tutorial. 4949 4950If you like GNU \ **parallel**\ : 4951 4952 4953- \* 4954 4955 (Re-)walk through the tutorial if you have not done so in the past year 4956 (https://www.gnu.org/software/parallel/parallel_tutorial.html) 4957 4958 4959 4960- \* 4961 4962 Give a demo at your local user group/your team/your colleagues 4963 4964 4965 4966- \* 4967 4968 Post the intro videos and the tutorial on Reddit, Mastodon, Diaspora\*, 4969 forums, blogs, Identi.ca, Google+, Twitter, Facebook, Linkedin, and 4970 mailing lists 4971 4972 4973 4974- \* 4975 4976 Request or write a review for your favourite blog or magazine 4977 (especially if you do something cool with GNU \ **parallel**\ ) 4978 4979 4980 4981- \* 4982 4983 Invite me for your next conference 4984 4985 4986 4987If you use GNU \ **parallel**\ for research: 4988 4989 4990- \* 4991 4992 Please cite GNU \ **parallel**\ in you publications (use \ **--citation**\ ) 4993 4994 4995 4996If GNU \ **parallel**\ saves you money: 4997 4998 4999- \* 5000 5001 (Have your company) donate to FSF or become a member 5002 https://my.fsf.org/donate/ 5003 5004 5005 5006(C) 2013-2021 Ole Tange, GFDLv1.3+ (See 5007LICENSES/GFDL-1.3-or-later.txt) 5008 5009