1.\" $OpenBSD: patch.1,v 1.22 2008/06/06 20:44:00 jmc 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 April 10, 2013 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 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 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 over-ruled by a 61.Fl c , 62.Fl e , 63.Fl n , 64or 65.Fl u 66option. 67Context diffs (old-style, new-style, and unified) and 68normal diffs are applied directly by the 69.Nm 70program itself, whereas ed diffs are simply fed to the 71.Xr ed 1 72editor via a pipe. 73.Pp 74If the 75.Ar patchfile 76contains more than one patch, 77.Nm 78will try to apply each of them as if they came from separate patch files. 79This means, among other things, that it is assumed that the name of the file 80to patch must be determined for each diff listing, and that the garbage before 81each diff listing will be examined for interesting things such as file names 82and revision level (see the section on 83.Sx Filename Determination 84below). 85.Pp 86The options are as follows: 87.Bl -tag -width Ds 88.It Xo 89.Fl B Ar backup-prefix , 90.Fl Fl prefix Ar backup-prefix 91.Xc 92Causes the next argument to be interpreted as a prefix to the backup file 93name. 94If this argument is specified, any argument to 95.Fl z 96will be ignored. 97.It Fl b , Fl Fl backup 98Save a backup copy of the file before it is modified. 99By default the original file is saved with a backup extension of 100.Qq .orig 101unless the file already has a numbered backup, in which case a numbered 102backup is made. 103This is equivalent to specifying 104.Qo Fl V Cm existing Qc . 105This option is currently the default, unless 106.Fl -posix 107is specified. 108.It Fl C , Fl Fl check 109Checks that the patch would apply cleanly, but does not modify anything. 110.It Fl c , Fl Fl context 111Forces 112.Nm 113to interpret the patch file as a context diff. 114.It Xo 115.Fl D Ar symbol , 116.Fl Fl ifdef Ar symbol 117.Xc 118Causes 119.Nm 120to use the 121.Qq #ifdef...#endif 122construct to mark changes. 123The argument following will be used as the differentiating symbol. 124Note that, unlike the C compiler, there must be a space between the 125.Fl D 126and the argument. 127.It Xo 128.Fl d Ar directory , 129.Fl Fl directory Ar directory 130.Xc 131Causes 132.Nm 133to interpret the next argument as a directory, 134and change the working directory to it before doing anything else. 135.It Fl E , Fl Fl remove-empty-files 136Causes 137.Nm 138to remove output files that are empty after the patches have been applied. 139This option is useful when applying patches that create or remove files. 140.It Fl e , Fl Fl ed 141Forces 142.Nm 143to interpret the patch file as an 144.Xr ed 1 145script. 146.It Xo 147.Fl F Ar max-fuzz , 148.Fl Fl fuzz Ar max-fuzz 149.Xc 150Sets the maximum fuzz factor. 151This option only applies to context diffs, and causes 152.Nm 153to ignore up to that many lines in looking for places to install a hunk. 154Note that a larger fuzz factor increases the odds of a faulty patch. 155The default fuzz factor is 2, and it may not be set to more than 156the number of lines of context in the context diff, ordinarily 3. 157.It Fl f , Fl Fl force 158Forces 159.Nm 160to assume that the user knows exactly what he or she is doing, and to not 161ask any questions. 162It assumes the following: 163skip patches for which a file to patch can't be found; 164patch files even though they have the wrong version for the 165.Qq Prereq: 166line in the patch; 167and assume that patches are not reversed even if they look like they are. 168This option does not suppress commentary; use 169.Fl s 170for that. 171.It Xo 172.Fl i Ar patchfile , 173.Fl Fl input Ar patchfile 174.Xc 175Causes the next argument to be interpreted as the input file name 176(i.e. a patchfile). 177This option may be specified multiple times. 178.It Fl l , Fl Fl ignore-whitespace 179Causes the pattern matching to be done loosely, in case the tabs and 180spaces have been munged in your input file. 181Any sequence of whitespace in the pattern line will match any sequence 182in the input file. 183Normal characters must still match exactly. 184Each line of the context must still match a line in the input file. 185.It Fl N , Fl Fl forward 186Causes 187.Nm 188to ignore patches that it thinks are reversed or already applied. 189See also 190.Fl R . 191.It Fl n , Fl Fl normal 192Forces 193.Nm 194to interpret the patch file as a normal diff. 195.It Xo 196.Fl o Ar out-file , 197.Fl Fl output Ar out-file 198.Xc 199Causes the next argument to be interpreted as the output file name. 200.It Xo 201.Fl p Ar strip-count , 202.Fl Fl strip Ar strip-count 203.Xc 204Sets the pathname strip count, 205which controls how pathnames found in the patch file are treated, 206in case you keep your files in a different directory than the person who sent 207out the patch. 208The strip count specifies how many slashes are to be stripped from 209the front of the pathname. 210(Any intervening directory names also go away.) 211For example, supposing the file name in the patch file was 212.Pa /u/howard/src/blurfl/blurfl.c : 213.Pp 214Setting 215.Fl p Ns Ar 0 216gives the entire pathname unmodified. 217.Pp 218.Fl p Ns Ar 1 219gives 220.Pp 221.D1 Pa u/howard/src/blurfl/blurfl.c 222.Pp 223without the leading slash. 224.Pp 225.Fl p Ns Ar 4 226gives 227.Pp 228.D1 Pa blurfl/blurfl.c 229.Pp 230Not specifying 231.Fl p 232at all just gives you 233.Pa blurfl.c , 234unless all of the directories in the leading path 235.Pq Pa u/howard/src/blurfl 236exist and that path is relative, 237in which case you get the entire pathname unmodified. 238Whatever you end up with is looked for either in the current directory, 239or the directory specified by the 240.Fl d 241option. 242.It Fl R , Fl Fl reverse 243Tells 244.Nm 245that this patch was created with the old and new files swapped. 246(Yes, I'm afraid that does happen occasionally, human nature being what it 247is.) 248.Nm 249will attempt to swap each hunk around before applying it. 250Rejects will come out in the swapped format. 251The 252.Fl R 253option will not work with ed diff scripts because there is too little 254information to reconstruct the reverse operation. 255.Pp 256If the first hunk of a patch fails, 257.Nm 258will reverse the hunk to see if it can be applied that way. 259If it can, you will be asked if you want to have the 260.Fl R 261option set. 262If it can't, the patch will continue to be applied normally. 263(Note: this method cannot detect a reversed patch if it is a normal diff 264and if the first command is an append (i.e. it should have been a delete) 265since appends always succeed, due to the fact that a null context will match 266anywhere. 267Luckily, most patches add or change lines rather than delete them, so most 268reversed normal diffs will begin with a delete, which will fail, triggering 269the heuristic.) 270.It Xo 271.Fl r Ar rej-name , 272.Fl Fl reject-file Ar rej-name 273.Xc 274Causes the next argument to be interpreted as the reject file name. 275.It Xo 276.Fl s , Fl Fl quiet , 277.Fl Fl silent 278.Xc 279Makes 280.Nm 281do its work silently, unless an error occurs. 282.It Fl t , Fl Fl batch 283Similar to 284.Fl f , 285in that it suppresses questions, but makes some different assumptions: 286skip patches for which a file to patch can't be found (the same as 287.Fl f ) ; 288skip patches for which the file has the wrong version for the 289.Qq Prereq: 290line in the patch; 291and assume that patches are reversed if they look like they are. 292.It Fl u , Fl Fl unified 293Forces 294.Nm 295to interpret the patch file as a unified context diff (a unidiff). 296.It Xo 297.Fl V Cm t | nil | never , 298.Fl Fl version-control Cm t | nil | never 299.Xc 300Causes the next argument to be interpreted as a method for creating 301backup file names. 302The type of backups made can also be given in the 303.Ev PATCH_VERSION_CONTROL 304or 305.Ev VERSION_CONTROL 306environment variables, which are overridden by this option. 307The 308.Fl B 309option overrides this option, causing the prefix to always be used for 310making backup file names. 311The values of the 312.Ev PATCH_VERSION_CONTROL 313and 314.Ev VERSION_CONTROL 315environment variables and the argument to the 316.Fl V 317option are like the GNU Emacs 318.Dq version-control 319variable; they also recognize synonyms that are more descriptive. 320The valid values are (unique abbreviations are accepted): 321.Bl -tag -width Ds -offset indent 322.It Cm t , numbered 323Always make numbered backups. 324.It Cm nil , existing 325Make numbered backups of files that already have them, 326simple backups of the others. 327.It Cm never , simple 328Always make simple backups. 329.El 330.It Fl v , Fl Fl version 331Causes 332.Nm 333to print out its revision header and patch level. 334.It Xo 335.Fl x Ar number , 336.Fl Fl debug Ar number 337.Xc 338Sets internal debugging flags, and is of interest only to 339.Nm 340patchers. 341.It Xo 342.Fl z Ar backup-ext , 343.Fl Fl suffix Ar backup-ext 344.Xc 345Causes the next argument to be interpreted as the backup extension, to be 346used in place of 347.Qq .orig . 348.It Fl Fl posix 349Enables strict 350.St -p1003.1-2004 351conformance, specifically: 352.Bl -enum 353.It 354Backup files are not created unless the 355.Fl b 356option is specified. 357.It 358If unspecified, the file name used is the first of the old, new and 359index files that exists. 360.El 361.El 362.Ss Patch Application 363.Nm 364will try to skip any leading garbage, apply the diff, 365and then skip any trailing garbage. 366Thus you could feed an article or message containing a 367diff listing to 368.Nm , 369and it should work. 370If the entire diff is indented by a consistent amount, 371this will be taken into account. 372.Pp 373With context diffs, and to a lesser extent with normal diffs, 374.Nm 375can detect when the line numbers mentioned in the patch are incorrect, 376and will attempt to find the correct place to apply each hunk of the patch. 377As a first guess, it takes the line number mentioned for the hunk, plus or 378minus any offset used in applying the previous hunk. 379If that is not the correct place, 380.Nm 381will scan both forwards and backwards for a set of lines matching the context 382given in the hunk. 383First 384.Nm 385looks for a place where all lines of the context match. 386If no such place is found, and it's a context diff, and the maximum fuzz factor 387is set to 1 or more, then another scan takes place ignoring the first and last 388line of context. 389If that fails, and the maximum fuzz factor is set to 2 or more, 390the first two and last two lines of context are ignored, 391and another scan is made. 392.Pq The default maximum fuzz factor is 2. 393.Pp 394If 395.Nm 396cannot find a place to install that hunk of the patch, it will put the hunk 397out to a reject file, which normally is the name of the output file plus 398.Qq .rej . 399(Note that the rejected hunk will come out in context diff form whether the 400input patch was a context diff or a normal diff. 401If the input was a normal diff, many of the contexts will simply be null.) 402The line numbers on the hunks in the reject file may be different than 403in the patch file: they reflect the approximate location patch thinks the 404failed hunks belong in the new file rather than the old one. 405.Pp 406As each hunk is completed, you will be told whether the hunk succeeded or 407failed, and which line (in the new file) 408.Nm 409thought the hunk should go on. 410If this is different from the line number specified in the diff, 411you will be told the offset. 412A single large offset MAY be an indication that a hunk was installed in the 413wrong place. 414You will also be told if a fuzz factor was used to make the match, in which 415case you should also be slightly suspicious. 416.Ss Filename Determination 417If no original file is specified on the command line, 418.Nm 419will try to figure out from the leading garbage what the name of the file 420to edit is. 421When checking a prospective file name, pathname components are stripped 422as specified by the 423.Fl p 424option and the file's existence and writability are checked relative 425to the current working directory (or the directory specified by the 426.Fl d 427option). 428.Pp 429If the diff is a context or unified diff, 430.Nm 431is able to determine the old and new file names from the diff header. 432For context diffs, the 433.Dq old 434file is specified in the line beginning with 435.Qq *** 436and the 437.Dq new 438file is specified in the line beginning with 439.Qq --- . 440For a unified diff, the 441.Dq old 442file is specified in the line beginning with 443.Qq --- 444and the 445.Dq new 446file is specified in the line beginning with 447.Qq +++ . 448If there is an 449.Qq Index: 450line in the leading garbage (regardless of the diff type), 451.Nm 452will use the file name from that line as the 453.Dq index 454file. 455.Pp 456.Nm 457will choose the file name by performing the following steps, with the first 458match used: 459.Bl -enum 460.It 461If 462.Nm 463is operating in strict 464.St -p1003.1-2004 465mode, the first of the 466.Dq old , 467.Dq new 468and 469.Dq index 470file names that exist is used. 471Otherwise, 472.Nm 473will examine either the 474.Dq old 475and 476.Dq new 477file names or, for a non-context diff, the 478.Dq index 479file name, and choose the file name with the fewest path components, 480the shortest basename, and the shortest total file name length (in that order). 481.It 482If no file exists, 483.Nm 484checks for the existence of the files in an SCCS or RCS directory 485(using the appropriate prefix or suffix) using the criteria specified 486above. 487If found, 488.Nm 489will attempt to get or check out the file. 490.It 491If no suitable file was found to patch, the patch file is a context or 492unified diff, and the old file was zero length, the new file name is 493created and used. 494.It 495If the file name still cannot be determined, 496.Nm 497will prompt the user for the file name to use. 498.El 499.Pp 500Additionally, if the leading garbage contains a 501.Qq Prereq:\ \& 502line, 503.Nm 504will take the first word from the prerequisites line (normally a version 505number) and check the input file to see if that word can be found. 506If not, 507.Nm 508will ask for confirmation before proceeding. 509.Pp 510The upshot of all this is that you should be able to say, while in a news 511interface, the following: 512.Pp 513.Dl | patch -d /usr/src/local/blurfl 514.Pp 515and patch a file in the blurfl directory directly from the article containing 516the patch. 517.Ss Backup Files 518By default, the patched version is put in place of the original, with 519the original file backed up to the same name with the extension 520.Qq .orig , 521or as specified by the 522.Fl B , 523.Fl V , 524or 525.Fl z 526options. 527The extension used for making backup files may also be specified in the 528.Ev SIMPLE_BACKUP_SUFFIX 529environment variable, which is overridden by the options above. 530.Pp 531If the backup file is a symbolic or hard link to the original file, 532.Nm 533creates a new backup file name by changing the first lowercase letter 534in the last component of the file's name into uppercase. 535If there are no more lowercase letters in the name, 536it removes the first character from the name. 537It repeats this process until it comes up with a 538backup file that does not already exist or is not linked to the original file. 539.Pp 540You may also specify where you want the output to go with the 541.Fl o 542option; if that file already exists, it is backed up first. 543.Ss Notes For Patch Senders 544There are several things you should bear in mind if you are going to 545be sending out patches: 546.Pp 547First, you can save people a lot of grief by keeping a 548.Pa patchlevel.h 549file which is patched to increment the patch level as the first diff in the 550patch file you send out. 551If you put a 552.Qq Prereq: 553line in with the patch, it won't let them apply 554patches out of order without some warning. 555.Pp 556Second, make sure you've specified the file names right, either in a 557context diff header, or with an 558.Qq Index: 559line. 560If you are patching something in a subdirectory, be sure to tell the patch 561user to specify a 562.Fl p 563option as needed. 564.Pp 565Third, you can create a file by sending out a diff that compares a 566null file to the file you want to create. 567This will only work if the file you want to create doesn't exist already in 568the target directory. 569.Pp 570Fourth, take care not to send out reversed patches, since it makes people wonder 571whether they already applied the patch. 572.Pp 573Fifth, while you may be able to get away with putting 582 diff listings into 574one file, it is probably wiser to group related patches into separate files in 575case something goes haywire. 576.Sh ENVIRONMENT 577.Bl -tag -width "PATCH_VERSION_CONTROL" -compact 578.It Ev POSIXLY_CORRECT 579When set, 580.Nm 581behaves as if the 582.Fl Fl posix 583option has been specified. 584.It Ev SIMPLE_BACKUP_SUFFIX 585Extension to use for backup file names instead of 586.Qq .orig . 587.It Ev TMPDIR 588Directory to put temporary files in; default is 589.Pa /tmp . 590.It Ev PATCH_VERSION_CONTROL 591Selects when numbered backup files are made. 592.It Ev VERSION_CONTROL 593Same as 594.Ev PATCH_VERSION_CONTROL . 595.El 596.Sh FILES 597.Bl -tag -width "$TMPDIR/patch*" -compact 598.It Pa $TMPDIR/patch* 599.Nm 600temporary files 601.It Pa /dev/tty 602used to read input when 603.Nm 604prompts the user 605.El 606.Sh EXIT STATUS 607The 608.Nm 609utility exits with one of the following values: 610.Pp 611.Bl -tag -width Ds -compact -offset indent 612.It \&0 613Successful completion. 614.It \&1 615One or more lines were written to a reject file. 616.It \*[Gt]\&1 617An error occurred. 618.El 619.Pp 620When applying a set of patches in a loop it behooves you to check this 621exit status so you don't apply a later patch to a partially patched file. 622.Sh DIAGNOSTICS 623Too many to list here, but generally indicative that 624.Nm 625couldn't parse your patch file. 626.Pp 627The message 628.Qq Hmm... 629indicates that there is unprocessed text in the patch file and that 630.Nm 631is attempting to intuit whether there is a patch in that text and, if so, 632what kind of patch it is. 633.Sh SEE ALSO 634.Xr diff 1 635.Sh STANDARDS 636The 637.Nm 638utility is compliant with the 639.St -p1003.1-2004 640specification 641(except as detailed above for the 642.Fl -posix 643option), 644though the presence of 645.Nm 646itself is optional. 647.Pp 648The flags 649.Op Fl CEfstuvBFVxz 650and 651.Op Fl -posix 652are extensions to that specification. 653.Sh AUTHORS 654.An Larry Wall 655with many other contributors. 656.Sh CAVEATS 657.Nm 658cannot tell if the line numbers are off in an ed script, and can only detect 659bad line numbers in a normal diff when it finds a 660.Qq change 661or a 662.Qq delete 663command. 664A context diff using fuzz factor 3 may have the same problem. 665Until a suitable interactive interface is added, you should probably do 666a context diff in these cases to see if the changes made sense. 667Of course, compiling without errors is a pretty good indication that the patch 668worked, but not always. 669.Pp 670.Nm 671usually produces the correct results, even when it has to do a lot of 672guessing. 673However, the results are guaranteed to be correct only when the patch is 674applied to exactly the same version of the file that the patch was 675generated from. 676.Sh BUGS 677Could be smarter about partial matches, excessively deviant offsets and 678swapped code, but that would take an extra pass. 679.Pp 680Check patch mode 681.Pq Fl C 682will fail if you try to check several patches in succession that build on 683each other. 684The entire 685.Nm 686code would have to be restructured to keep temporary files around so that it 687can handle this situation. 688.Pp 689If code has been duplicated (for instance with #ifdef OLDCODE ... #else ... 690#endif), 691.Nm 692is incapable of patching both versions, and, if it works at all, will likely 693patch the wrong one, and tell you that it succeeded to boot. 694.Pp 695If you apply a patch you've already applied, 696.Nm 697will think it is a reversed patch, and offer to un-apply the patch. 698This could be construed as a feature. 699