1.\" $OpenBSD: patch.1,v 1.32 2018/06/22 15:37:15 zhuk Exp $ 2.\" Copyright 1986, Larry Wall 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following condition 6.\" is met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this condition and the following disclaimer. 9.\" 10.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 11.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 12.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 13.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 14.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 15.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 16.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 17.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 18.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 19.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 20.\" SUCH DAMAGE. 21.\" 22.Dd $Mdocdate: June 22 2018 $ 23.Dt PATCH 1 24.Os 25.Sh NAME 26.Nm patch 27.Nd apply a diff file to an original 28.Sh SYNOPSIS 29.Nm patch 30.Bk -words 31.Op Fl bCcEeflNnRstuv 32.Op Fl B Ar backup-prefix 33.Op Fl D Ar symbol 34.Op Fl d Ar directory 35.Op Fl F Ar max-fuzz 36.Op Fl i Ar patchfile 37.Op Fl o Ar out-file 38.Op Fl p Ar strip-count 39.Op Fl r Ar rej-name 40.Op Fl V Cm t | nil | never 41.Op Fl x Ar number 42.Op Fl z Ar backup-ext 43.Op Fl Fl posix 44.Op Ar origfile Op Ar patchfile 45.Ek 46.Nm patch 47.Pf \*(Lt Ar patchfile 48.Sh DESCRIPTION 49.Nm 50will take a patch file containing any of the four forms of difference 51listing produced by the 52.Xr diff 1 53program and apply those differences to an original file, 54producing a patched version. 55If 56.Ar patchfile 57is omitted, or is a hyphen, the patch will be read from the standard input. 58.Pp 59.Nm 60will attempt to determine the type of the diff listing, unless overruled by a 61.Fl c , 62.Fl e , 63.Fl n , 64or 65.Fl u 66option. 67.Pp 68If the 69.Ar patchfile 70contains more than one patch, 71.Nm 72will try to apply each of them as if they came from separate patch files. 73This means, among other things, that it is assumed that the name of the file 74to patch must be determined for each diff listing, and that the garbage before 75each diff listing will be examined for interesting things such as file names 76and revision level (see the section on 77.Sx Filename Determination 78below). 79.Pp 80The options are as follows: 81.Bl -tag -width Ds 82.It Xo 83.Fl B Ar backup-prefix , 84.Fl Fl prefix Ar backup-prefix 85.Xc 86Causes the next argument to be interpreted as a prefix to the backup file 87name. 88If this argument is specified, any argument to 89.Fl z 90will be ignored. 91.It Fl b , Fl Fl backup 92Save a backup copy of the file before it is modified. 93By default the original file is saved with a backup extension of 94.Qq .orig 95unless the file already has a numbered backup, in which case a numbered 96backup is made. 97This is equivalent to specifying 98.Qo Fl V Cm existing Qc . 99This option is currently the default, unless 100.Fl -posix 101is specified. 102.It Fl C , Fl Fl check , Fl Fl dry-run 103Checks that the patch would apply cleanly, but does not modify anything. 104.It Fl c , Fl Fl context 105Forces 106.Nm 107to interpret the patch file as a context diff. 108.It Xo 109.Fl D Ar symbol , 110.Fl Fl ifdef Ar symbol 111.Xc 112Causes 113.Nm 114to use the 115.Qq #ifdef...#endif 116construct to mark changes. 117The argument following will be used as the differentiating symbol. 118Note that, unlike the C compiler, there must be a space between the 119.Fl D 120and the argument. 121.It Xo 122.Fl d Ar directory , 123.Fl Fl directory Ar directory 124.Xc 125Causes 126.Nm 127to interpret the next argument as a directory, 128and change working directory to it before doing anything else. 129.It Fl E , Fl Fl remove-empty-files 130Causes 131.Nm 132to remove output files that are empty after the patches have been applied. 133This option is useful when applying patches that create or remove files. 134.It Fl e , Fl Fl ed 135Forces 136.Nm 137to interpret the patch file as an 138.Xr ed 1 139script. 140.It Xo 141.Fl F Ar max-fuzz , 142.Fl Fl fuzz Ar max-fuzz 143.Xc 144Sets the maximum fuzz factor. 145This option only applies to context diffs, and causes 146.Nm 147to ignore up to that many lines in looking for places to install a hunk. 148Note that a larger fuzz factor increases the odds of a faulty patch. 149The default fuzz factor is 2, and it may not be set to more than 150the number of lines of context in the context diff, ordinarily 3. 151.It Fl f , Fl Fl force 152Forces 153.Nm 154to assume that the user knows exactly what he or she is doing, and to not 155ask any questions. 156It assumes the following: 157skip patches for which a file to patch can't be found; 158patch files even though they have the wrong version for the 159.Qq Prereq: 160line in the patch; 161and assume that patches are not reversed even if they look like they are. 162This option does not suppress commentary; use 163.Fl s 164for that. 165.It Xo 166.Fl i Ar patchfile , 167.Fl Fl input Ar patchfile 168.Xc 169Causes the next argument to be interpreted as the input file name 170(i.e. a patchfile). 171This option may be specified multiple times. 172.It Fl l , Fl Fl ignore-whitespace 173Causes the pattern matching to be done loosely, in case the tabs and 174spaces have been munged in your input file. 175Any sequence of whitespace in the pattern line will match any sequence 176in the input file. 177Normal characters must still match exactly. 178Each line of the context must still match a line in the input file. 179.It Fl N , Fl Fl forward 180Causes 181.Nm 182to ignore patches that it thinks are reversed or already applied. 183See also 184.Fl R . 185.It Fl n , Fl Fl normal 186Forces 187.Nm 188to interpret the patch file as a normal diff. 189.It Xo 190.Fl o Ar out-file , 191.Fl Fl output Ar out-file 192.Xc 193Causes the next argument to be interpreted as the output file name. 194.It Xo 195.Fl p Ar strip-count , 196.Fl Fl strip Ar strip-count 197.Xc 198Sets the pathname strip count, 199which controls how pathnames found in the patch file are treated, 200in case you keep your files in a different directory than the person who sent 201out the patch. 202The strip count specifies how many slashes are to be stripped from 203the front of the pathname. 204(Any intervening directory names also go away.) 205For example, supposing the file name in the patch file was 206.Pa /u/howard/src/blurfl/blurfl.c : 207.Pp 208Setting 209.Fl p Ns Ar 0 210gives the entire pathname unmodified. 211.Pp 212.Fl p Ns Ar 1 213gives 214.Pp 215.D1 Pa u/howard/src/blurfl/blurfl.c 216.Pp 217without the leading slash. 218.Pp 219.Fl p Ns Ar 4 220gives 221.Pp 222.D1 Pa blurfl/blurfl.c 223.Pp 224Not specifying 225.Fl p 226at all just gives you 227.Pa blurfl.c , 228unless all of the directories in the leading path 229.Pq Pa u/howard/src/blurfl 230exist and that path is relative, 231in which case you get the entire pathname unmodified. 232Whatever you end up with is looked for either in the current directory, 233or the directory specified by the 234.Fl d 235option. 236.It Fl R , Fl Fl reverse 237Tells 238.Nm 239that this patch was created with the old and new files swapped. 240(Yes, I'm afraid that does happen occasionally, human nature being what it 241is.) 242.Nm 243will attempt to swap each hunk around before applying it. 244Rejects will come out in the swapped format. 245The 246.Fl R 247option will not work with ed diff scripts because there is too little 248information to reconstruct the reverse operation. 249.Pp 250If the first hunk of a patch fails, 251.Nm 252will reverse the hunk to see if it can be applied that way. 253If it can, you will be asked if you want to have the 254.Fl R 255option set. 256If it can't, the patch will continue to be applied normally. 257(Note: this method cannot detect a reversed patch if it is a normal diff 258and if the first command is an append (i.e. it should have been a delete) 259since appends always succeed, due to the fact that a null context will match 260anywhere. 261Luckily, most patches add or change lines rather than delete them, so most 262reversed normal diffs will begin with a delete, which will fail, triggering 263the heuristic.) 264.It Xo 265.Fl r Ar rej-name , 266.Fl Fl reject-file Ar rej-name 267.Xc 268Causes the next argument to be interpreted as the reject file name. 269.It Xo 270.Fl s , Fl Fl quiet , 271.Fl Fl silent 272.Xc 273Makes 274.Nm 275do its work silently, unless an error occurs. 276.It Fl t , Fl Fl batch 277Similar to 278.Fl f , 279in that it suppresses questions, but makes some different assumptions: 280skip patches for which a file to patch can't be found (the same as 281.Fl f ) ; 282skip patches for which the file has the wrong version for the 283.Qq Prereq: 284line in the patch; 285and assume that patches are reversed if they look like they are. 286.It Fl u , Fl Fl unified 287Forces 288.Nm 289to interpret the patch file as a unified context diff (a unidiff). 290.It Xo 291.Fl V Cm t | nil | never , 292.Fl Fl version-control Cm t | nil | never 293.Xc 294Causes the next argument to be interpreted as a method for creating 295backup file names. 296The type of backups made can also be given in the 297.Ev PATCH_VERSION_CONTROL 298or 299.Ev VERSION_CONTROL 300environment variables, which are overridden by this option. 301The 302.Fl B 303option overrides this option, causing the prefix to always be used for 304making backup file names. 305The values of the 306.Ev PATCH_VERSION_CONTROL 307and 308.Ev VERSION_CONTROL 309environment variables and the argument to the 310.Fl V 311option are like the GNU Emacs 312.Dq version-control 313variable; they also recognize synonyms that are more descriptive. 314The valid values are (unique abbreviations are accepted): 315.Bl -tag -width Ds -offset indent 316.It Cm t , numbered 317Always make numbered backups. 318.It Cm nil , existing 319Make numbered backups of files that already have them, 320simple backups of the others. 321.It Cm never , simple 322Always make simple backups. 323.El 324.It Fl v , Fl Fl version 325Causes 326.Nm 327to print out its revision header and patch level. 328.It Xo 329.Fl x Ar number , 330.Fl Fl debug Ar number 331.Xc 332Sets internal debugging flags, and is of interest only to 333.Nm 334patchers. 335.It Xo 336.Fl z Ar backup-ext , 337.Fl Fl suffix Ar backup-ext 338.Xc 339Causes the next argument to be interpreted as the backup extension, to be 340used in place of 341.Qq .orig . 342.It Fl Fl posix 343Enables strict 344.St -p1003.1-2008 345conformance, specifically: 346.Bl -enum 347.It 348Backup files are not created unless the 349.Fl b 350option is specified. 351.It 352If unspecified, the file name used is the first of the old, new and 353index files that exists. 354.El 355.El 356.Ss Patch Application 357.Nm 358will try to skip any leading garbage, apply the diff, 359and then skip any trailing garbage. 360Thus you could feed an article or message containing a 361diff listing to 362.Nm patch , 363and it should work. 364If the entire diff is indented by a consistent amount, 365this will be taken into account. 366.Pp 367With context diffs, and to a lesser extent with normal diffs, 368.Nm 369can detect when the line numbers mentioned in the patch are incorrect, 370and will attempt to find the correct place to apply each hunk of the patch. 371As a first guess, it takes the line number mentioned for the hunk, plus or 372minus any offset used in applying the previous hunk. 373If that is not the correct place, 374.Nm 375will scan both forwards and backwards for a set of lines matching the context 376given in the hunk. 377First 378.Nm 379looks for a place where all lines of the context match. 380If no such place is found, and it's a context diff, and the maximum fuzz factor 381is set to 1 or more, then another scan takes place ignoring the first and last 382line of context. 383If that fails, and the maximum fuzz factor is set to 2 or more, 384the first two and last two lines of context are ignored, 385and another scan is made. 386.Pq The default maximum fuzz factor is 2. 387.Pp 388If 389.Nm 390cannot find a place to install that hunk of the patch, it will put the hunk 391out to a reject file, which normally is the name of the output file plus 392.Qq .rej . 393(Note that the rejected hunk will come out in context diff form whether the 394input patch was a context diff or a normal diff. 395If the input was a normal diff, many of the contexts will simply be null.) 396The line numbers on the hunks in the reject file may be different than 397in the patch file: they reflect the approximate location patch thinks the 398failed hunks belong in the new file rather than the old one. 399.Pp 400As each hunk is completed, you will be told whether the hunk succeeded or 401failed, and which line (in the new file) 402.Nm 403thought the hunk should go on. 404If this is different from the line number specified in the diff, 405you will be told the offset. 406A single large offset MAY be an indication that a hunk was installed in the 407wrong place. 408You will also be told if a fuzz factor was used to make the match, in which 409case you should also be slightly suspicious. 410.Ss Filename Determination 411If no original file is specified on the command line, 412.Nm 413will try to figure out from the leading garbage what the name of the file 414to edit is. 415When checking a prospective file name, pathname components are stripped 416as specified by the 417.Fl p 418option and the file's existence and writability are checked relative 419to the current working directory (or the directory specified by the 420.Fl d 421option). 422.Pp 423If the diff is a context or unified diff, 424.Nm 425is able to determine the old and new file names from the diff header. 426For context diffs, the 427.Dq old 428file is specified in the line beginning with 429.Qq *** 430and the 431.Dq new 432file is specified in the line beginning with 433.Qq --- . 434For a unified diff, the 435.Dq old 436file is specified in the line beginning with 437.Qq --- 438and the 439.Dq new 440file is specified in the line beginning with 441.Qq +++ . 442If there is an 443.Qq Index: 444line in the leading garbage (regardless of the diff type), 445.Nm 446will use the file name from that line as the 447.Dq index 448file. 449.Pp 450.Nm 451will choose the file name by performing the following steps, with the first 452match used: 453.Bl -enum 454.It 455If 456.Nm 457is operating in strict 458.St -p1003.1-2008 459mode, the first of the 460.Dq old , 461.Dq new 462and 463.Dq index 464file names that exist is used. 465Otherwise, 466.Nm 467will examine either the 468.Dq old 469and 470.Dq new 471file names or, for a non-context diff, the 472.Dq index 473file name, and choose the file name with the fewest path components, 474the shortest basename, and the shortest total file name length (in that order). 475.It 476If no suitable file was found to patch, the patch file is a context or 477unified diff, and the old file was zero length, the new file name is 478created and used. 479.It 480If the file name still cannot be determined, 481.Nm 482will prompt the user for the file name to use. 483.El 484.Pp 485Additionally, if the leading garbage contains a 486.Qq Prereq:\ \& 487line, 488.Nm 489will take the first word from the prerequisites line (normally a version 490number) and check the input file to see if that word can be found. 491If not, 492.Nm 493will ask for confirmation before proceeding. 494.Pp 495The upshot of all this is that you should be able to say, while in a news 496interface, the following: 497.Pp 498.Dl | patch -d /usr/src/local/blurfl 499.Pp 500and patch a file in the blurfl directory directly from the article containing 501the patch. 502.Ss Backup Files 503By default, the patched version is put in place of the original, with 504the original file backed up to the same name with the extension 505.Qq .orig , 506or as specified by the 507.Fl B , 508.Fl V , 509or 510.Fl z 511options. 512The extension used for making backup files may also be specified in the 513.Ev SIMPLE_BACKUP_SUFFIX 514environment variable, which is overridden by the options above. 515.Pp 516If the backup file is a symbolic or hard link to the original file, 517.Nm 518creates a new backup file name by changing the first lowercase letter 519in the last component of the file's name into uppercase. 520If there are no more lowercase letters in the name, 521it removes the first character from the name. 522It repeats this process until it comes up with a 523backup file that does not already exist or is not linked to the original file. 524.Pp 525You may also specify where you want the output to go with the 526.Fl o 527option; if that file already exists, it is backed up first. 528.Ss Notes For Patch Senders 529There are several things you should bear in mind if you are going to 530be sending out patches: 531.Pp 532First, you can save people a lot of grief by keeping a 533.Pa patchlevel.h 534file which is patched to increment the patch level as the first diff in the 535patch file you send out. 536If you put a 537.Qq Prereq: 538line in with the patch, it won't let them apply 539patches out of order without some warning. 540.Pp 541Second, make sure you've specified the file names right, either in a 542context diff header, or with an 543.Qq Index: 544line. 545If you are patching something in a subdirectory, be sure to tell the patch 546user to specify a 547.Fl p 548option as needed. 549.Pp 550Third, you can create a file by sending out a diff that compares a 551null file to the file you want to create. 552This will only work if the file you want to create doesn't exist already in 553the target directory. 554.Pp 555Fourth, take care not to send out reversed patches, since it makes people wonder 556whether they already applied the patch. 557.Pp 558Fifth, while you may be able to get away with putting 582 diff listings into 559one file, it is probably wiser to group related patches into separate files in 560case something goes haywire. 561.Sh ENVIRONMENT 562.Bl -tag -width "PATCH_VERSION_CONTROL" -compact 563.It Ev POSIXLY_CORRECT 564When set, 565.Nm 566behaves as if the 567.Fl Fl posix 568option has been specified. 569.It Ev SIMPLE_BACKUP_SUFFIX 570Extension to use for backup file names instead of 571.Qq .orig . 572.It Ev TMPDIR 573Directory to put temporary files in; default is 574.Pa /tmp . 575.It Ev PATCH_VERSION_CONTROL 576Selects when numbered backup files are made. 577.It Ev VERSION_CONTROL 578Same as 579.Ev PATCH_VERSION_CONTROL . 580.El 581.Sh FILES 582.Bl -tag -width "$TMPDIR/patch*" -compact 583.It Pa $TMPDIR/patch* 584.Nm 585temporary files 586.It Pa /dev/tty 587used to read input when 588.Nm 589prompts the user 590.El 591.Sh EXIT STATUS 592The 593.Nm 594utility exits with one of the following values: 595.Pp 596.Bl -tag -width Ds -offset indent -compact 597.It 0 598Successful completion. 599.It 1 600One or more lines were written to a reject file. 601.It \*(Gt1 602An error occurred. 603.El 604.Pp 605When applying a set of patches in a loop it behooves you to check this 606exit status so you don't apply a later patch to a partially patched file. 607.Sh DIAGNOSTICS 608Too many to list here, but generally indicative that 609.Nm 610couldn't parse your patch file. 611.Pp 612The message 613.Qq Hmm... 614indicates that there is unprocessed text in the patch file and that 615.Nm 616is attempting to intuit whether there is a patch in that text and, if so, 617what kind of patch it is. 618.Sh SEE ALSO 619.Xr diff 1 620.Sh STANDARDS 621The 622.Nm 623utility is compliant with the 624.St -p1003.1-2008 625specification, 626except as detailed above for the 627.Fl -posix 628option. 629.Pp 630The flags 631.Op Fl BCEFfstVvxz 632and 633.Op Fl -posix 634are extensions to that specification. 635.Sh AUTHORS 636.An Larry Wall 637with many other contributors. 638.Sh CAVEATS 639.Nm 640cannot tell if the line numbers are off in an ed script, and can only detect 641bad line numbers in a normal diff when it finds a 642.Qq change 643or a 644.Qq delete 645command. 646A context diff using fuzz factor 3 may have the same problem. 647Until a suitable interactive interface is added, you should probably do 648a context diff in these cases to see if the changes made sense. 649Of course, compiling without errors is a pretty good indication that the patch 650worked, but not always. 651.Pp 652.Nm 653usually produces the correct results, even when it has to do a lot of 654guessing. 655However, the results are guaranteed to be correct only when the patch is 656applied to exactly the same version of the file that the patch was 657generated from. 658.Sh BUGS 659Could be smarter about partial matches, excessively deviant offsets and 660swapped code, but that would take an extra pass. 661.Pp 662Check patch mode 663.Pq Fl C 664will fail if you try to check several patches in succession that build on 665each other. 666The entire 667.Nm 668code would have to be restructured to keep temporary files around so that it 669can handle this situation. 670.Pp 671If code has been duplicated (for instance with #ifdef OLDCODE ... #else ... 672#endif), 673.Nm 674is incapable of patching both versions and, if it works at all, will likely 675patch the wrong one, and tell you that it succeeded to boot. 676.Pp 677If you apply a patch you've already applied, 678.Nm 679will think it is a reversed patch, and offer to un-apply the patch. 680This could be construed as a feature. 681