1.\" $OpenBSD: patch.1,v 1.22 2008/06/06 20:44:00 jmc Exp $ 2.\" $DragonFly: src/usr.bin/patch/patch.1,v 1.10 2008/08/18 19:15:55 joerg Exp $ 3.\" $NetBSD: patch.1,v 1.21 2017/07/03 21:34:20 wiz Exp $ 4.\" Copyright 1986, Larry Wall 5.\" 6.\" Redistribution and use in source and binary forms, with or without 7.\" modification, are permitted provided that the following condition 8.\" is met: 9.\" 1. Redistributions of source code must retain the above copyright 10.\" notice, this condition and the following disclaimer. 11.\" 12.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 13.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 14.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 15.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 16.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 17.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 18.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 19.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 20.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 21.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 22.\" SUCH DAMAGE. 23.\" 24.Dd November 7, 2015 25.Dt PATCH 1 26.Os 27.Sh NAME 28.Nm patch 29.Nd apply a diff file to an original 30.Sh SYNOPSIS 31.Nm 32.Op Fl bCcEeflNnRstuv 33.Op Fl B Ar backup-prefix 34.Op Fl D Ar symbol 35.Op Fl d Ar directory 36.Op Fl F Ar max-fuzz 37.Op Fl i Ar patchfile 38.Op Fl o Ar out-file 39.Op Fl p Ar strip-count 40.Op Fl r Ar rej-name 41.Op Fl V Cm t | nil | never | none 42.Op Fl x Ar number 43.Op Fl z Ar backup-ext 44.Op Fl Fl posix 45.Op Ar origfile Op Ar patchfile 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 Fl B Ar backup-prefix , Fl Fl prefix Ar backup-prefix 89Causes the next argument to be interpreted as a prefix to the backup file 90name. 91If this argument is specified, any argument to 92.Fl z 93will be ignored. 94.It Fl b , Fl Fl backup 95Save a backup copy of the file before it is modified. 96By default the original file is saved with a backup extension of 97.Qq .orig 98unless the file already has a numbered backup, in which case a numbered 99backup is made. 100This is equivalent to specifying 101.Qo Fl V Cm existing Qc . 102This option is currently the default, unless 103.Fl -posix 104is specified. 105.It Fl C , Fl Fl check 106Checks that the patch would apply cleanly, but does not modify anything. 107.It Fl c , Fl Fl context 108Forces 109.Nm 110to interpret the patch file as a context diff. 111.It Fl D Ar symbol , Fl Fl ifdef Ar symbol 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 Fl d Ar directory , Fl Fl directory Ar directory 122Causes 123.Nm 124to interpret the next argument as a directory, 125and change the working directory to it before doing anything else. 126.It Fl E , Fl Fl remove-empty-files 127Causes 128.Nm 129to remove output files that are empty after the patches have been applied. 130This option is useful when applying patches that create or remove files. 131.It Fl e , Fl Fl ed 132Forces 133.Nm 134to interpret the patch file as an 135.Xr ed 1 136script. 137.It Fl F Ar max-fuzz , Fl Fl fuzz Ar max-fuzz 138Sets the maximum fuzz factor. 139This option only applies to context diffs, and causes 140.Nm 141to ignore up to that many lines in looking for places to install a hunk. 142Note that a larger fuzz factor increases the odds of a faulty patch. 143The default fuzz factor is 2, and it may not be set to more than 144the number of lines of context in the context diff, ordinarily 3. 145.It Fl f , Fl Fl force 146Forces 147.Nm 148to assume that the user knows exactly what he or she is doing, and to not 149ask any questions. 150It assumes the following: 151skip patches for which a file to patch can't be found; 152patch files even though they have the wrong version for the 153.Qq Prereq: 154line in the patch; 155and assume that patches are not reversed even if they look like they are. 156This option does not suppress commentary; use 157.Fl s 158for that. 159.It Fl i Ar patchfile , Fl Fl input Ar patchfile 160Causes the next argument to be interpreted as the input file name 161(i.e., a patchfile). 162This option may be specified multiple times. 163.It Fl l , Fl Fl ignore-whitespace 164Causes the pattern matching to be done loosely, in case the tabs and 165spaces have been munged in your input file. 166Any sequence of whitespace in the pattern line will match any sequence 167in the input file. 168Normal characters must still match exactly. 169Each line of the context must still match a line in the input file. 170.It Fl N , Fl Fl forward 171Causes 172.Nm 173to ignore patches that it thinks are reversed or already applied. 174See also 175.Fl R . 176.It Fl n , Fl Fl normal 177Forces 178.Nm 179to interpret the patch file as a normal diff. 180.It Fl o Ar out-file , Fl Fl output Ar out-file 181Causes the next argument to be interpreted as the output file name. 182.It Fl p Ar strip-count , Fl Fl strip Ar strip-count 183Sets the pathname strip count, 184which controls how pathnames found in the patch file are treated, 185in case you keep your files in a different directory than the person who sent 186out the patch. 187The strip count specifies how many slashes are to be stripped from 188the front of the pathname. 189(Any intervening directory names also go away.) 190For example, supposing the file name in the patch file was 191.Pa /u/howard/src/blurfl/blurfl.c : 192.Pp 193Setting 194.Fl p Ns Ar 0 195gives the entire pathname unmodified. 196.Pp 197.Fl p Ns Ar 1 198gives 199.Pp 200.D1 Pa u/howard/src/blurfl/blurfl.c 201.Pp 202without the leading slash. 203.Pp 204.Fl p Ns Ar 4 205gives 206.Pp 207.D1 Pa blurfl/blurfl.c 208.Pp 209Not specifying 210.Fl p 211at all just gives you 212.Pa blurfl.c , 213unless all of the directories in the leading path 214.Pq Pa u/howard/src/blurfl 215exist and that path is relative, 216in which case you get the entire pathname unmodified. 217Whatever you end up with is looked for either in the current directory, 218or the directory specified by the 219.Fl d 220option. 221.It Fl R , Fl Fl reverse 222Tells 223.Nm 224that this patch was created with the old and new files swapped. 225(Yes, I'm afraid that does happen occasionally, human nature being what it 226is.) 227.Nm 228will attempt to swap each hunk around before applying it. 229Rejects will come out in the swapped format. 230The 231.Fl R 232option will not work with ed diff scripts because there is too little 233information to reconstruct the reverse operation. 234.Pp 235If the first hunk of a patch fails, 236.Nm 237will reverse the hunk to see if it can be applied that way. 238If it can, you will be asked if you want to have the 239.Fl R 240option set. 241If it can't, the patch will continue to be applied normally. 242(Note: this method cannot detect a reversed patch if it is a normal diff 243and if the first command is an append (i.e., it should have been a delete) 244since appends always succeed, due to the fact that a null context will match 245anywhere. 246Luckily, most patches add or change lines rather than delete them, so most 247reversed normal diffs will begin with a delete, which will fail, triggering 248the heuristic.) 249.It Fl r Ar rej-name , Fl Fl reject-file Ar rej-name 250Causes the next argument to be interpreted as the reject file name. 251.It Fl s , Fl Fl quiet , Fl Fl silent 252Makes 253.Nm 254do its work silently, unless an error occurs. 255.It Fl t , Fl Fl batch 256Similar to 257.Fl f , 258in that it suppresses questions, but makes some different assumptions: 259skip patches for which a file to patch can't be found (the same as 260.Fl f ) ; 261skip patches for which the file has the wrong version for the 262.Qq Prereq: 263line in the patch; 264and assume that patches are reversed if they look like they are. 265.It Fl u , Fl Fl unified 266Forces 267.Nm 268to interpret the patch file as a unified context diff (a unidiff). 269.It Fl V Cm t | nil | never | none , Fl Fl version-control Cm t | nil | never | none 270Causes the next argument to be interpreted as a method for creating 271backup file names. 272The type of backups made can also be given in the 273.Ev PATCH_VERSION_CONTROL 274or 275.Ev VERSION_CONTROL 276environment variables, which are overridden by this option. 277The 278.Fl B 279option overrides this option, causing the prefix to always be used for 280making backup file names. 281The values of the 282.Ev PATCH_VERSION_CONTROL 283and 284.Ev VERSION_CONTROL 285environment variables and the argument to the 286.Fl V 287option are like the GNU Emacs 288.Dq version-control 289variable; they also recognize synonyms that are more descriptive. 290The valid values are (unique abbreviations are accepted): 291.Bl -tag -width Ds -offset indent 292.It Cm t , numbered 293Always make numbered backups. 294.It Cm nil , existing 295Make numbered backups of files that already have them, 296simple backups of the others. 297.It Cm never , simple 298Always make simple backups. 299.It Cm none 300No backups are created. 301.El 302.It Fl v , Fl Fl version 303Causes 304.Nm 305to print out its revision header and patch level. 306.It Fl x Ar number , Fl Fl debug Ar number 307Sets internal debugging flags, and is of interest only to 308.Nm 309patchers. 310.It Fl z Ar backup-ext , Fl Fl suffix Ar backup-ext 311Causes the next argument to be interpreted as the backup extension, to be 312used in place of 313.Qq .orig . 314.It Fl Fl posix 315Enables strict 316.St -p1003.1-2004 317conformance, specifically: 318.Bl -enum 319.It 320Backup files are not created unless the 321.Fl b 322option is specified. 323.It 324If unspecified, the file name used is the first of the old, new and 325index files that exists. 326.El 327.El 328.Ss Patch Application 329.Nm 330will try to skip any leading garbage, apply the diff, 331and then skip any trailing garbage. 332Thus you could feed an article or message containing a 333diff listing to 334.Nm , 335and it should work. 336If the entire diff is indented by a consistent amount, 337this will be taken into account. 338.Pp 339With context diffs, and to a lesser extent with normal diffs, 340.Nm 341can detect when the line numbers mentioned in the patch are incorrect, 342and will attempt to find the correct place to apply each hunk of the patch. 343As a first guess, it takes the line number mentioned for the hunk, plus or 344minus any offset used in applying the previous hunk. 345If that is not the correct place, 346.Nm 347will scan both forwards and backwards for a set of lines matching the context 348given in the hunk. 349First 350.Nm 351looks for a place where all lines of the context match. 352If no such place is found, and it's a context diff, and the maximum fuzz factor 353is set to 1 or more, then another scan takes place ignoring the first and last 354line of context. 355If that fails, and the maximum fuzz factor is set to 2 or more, 356the first two and last two lines of context are ignored, 357and another scan is made. 358.Pq The default maximum fuzz factor is 2. 359.Pp 360If 361.Nm 362cannot find a place to install that hunk of the patch, it will put the hunk 363out to a reject file, which normally is the name of the output file plus 364.Qq .rej . 365(Note that the rejected hunk will come out in context diff form whether the 366input patch was a context diff or a normal diff. 367If the input was a normal diff, many of the contexts will simply be null.) 368The line numbers on the hunks in the reject file may be different than 369in the patch file: they reflect the approximate location patch thinks the 370failed hunks belong in the new file rather than the old one. 371.Pp 372As each hunk is completed, you will be told whether the hunk succeeded or 373failed, and which line (in the new file) 374.Nm 375thought the hunk should go on. 376If this is different from the line number specified in the diff, 377you will be told the offset. 378A single large offset MAY be an indication that a hunk was installed in the 379wrong place. 380You will also be told if a fuzz factor was used to make the match, in which 381case you should also be slightly suspicious. 382.Ss Filename Determination 383If no original file is specified on the command line, 384.Nm 385will try to figure out from the leading garbage what the name of the file 386to edit is. 387When checking a prospective file name, pathname components are stripped 388as specified by the 389.Fl p 390option and the file's existence and writability are checked relative 391to the current working directory (or the directory specified by the 392.Fl d 393option). 394.Pp 395If the diff is a context or unified diff, 396.Nm 397is able to determine the old and new file names from the diff header. 398For context diffs, the 399.Dq old 400file is specified in the line beginning with 401.Qq *** 402and the 403.Dq new 404file is specified in the line beginning with 405.Qq --- . 406For a unified diff, the 407.Dq old 408file is specified in the line beginning with 409.Qq --- 410and the 411.Dq new 412file is specified in the line beginning with 413.Qq +++ . 414If there is an 415.Qq Index: 416line in the leading garbage (regardless of the diff type), 417.Nm 418will use the file name from that line as the 419.Dq index 420file. 421.Pp 422.Nm 423will choose the file name by performing the following steps, with the first 424match used: 425.Bl -enum 426.It 427If 428.Nm 429is operating in strict 430.St -p1003.1-2004 431mode, the first of the 432.Dq old , 433.Dq new 434and 435.Dq index 436file names that exist is used. 437Otherwise, 438.Nm 439will examine either the 440.Dq old 441and 442.Dq new 443file names or, for a non-context diff, the 444.Dq index 445file name, and choose the file name with the fewest path components, 446the shortest basename, and the shortest total file name length (in that order). 447.It 448If no file exists, 449.Nm 450checks for the existence of the files in an RCS directory using the criteria 451specified above. 452If found, 453.Nm 454will attempt to get or check out the file. 455.It 456If no suitable file was found to patch, the patch file is a context or 457unified diff, and the old file was zero length, the new file name is 458created and used. 459.It 460If the file name still cannot be determined, 461.Nm 462will prompt the user for the file name to use. 463.El 464.Pp 465Additionally, if the leading garbage contains a 466.Qq Prereq:\ \& 467line, 468.Nm 469will take the first word from the prerequisites line (normally a version 470number) and check the input file to see if that word can be found. 471If not, 472.Nm 473will ask for confirmation before proceeding. 474.Pp 475The upshot of all this is that you should be able to say, while in a news 476interface, the following: 477.Pp 478.Dl | patch -d /usr/src/local/blurfl 479.Pp 480and patch a file in the blurfl directory directly from the article containing 481the patch. 482.Ss Backup Files 483By default, the patched version is put in place of the original, with 484the original file backed up to the same name with the extension 485.Qq .orig , 486or as specified by the 487.Fl B , 488.Fl V , 489or 490.Fl z 491options. 492The extension used for making backup files may also be specified in the 493.Ev SIMPLE_BACKUP_SUFFIX 494environment variable, which is overridden by the options above. 495.Pp 496If the backup file is a symbolic or hard link to the original file, 497.Nm 498creates a new backup file name by changing the first lowercase letter 499in the last component of the file's name into uppercase. 500If there are no more lowercase letters in the name, 501it removes the first character from the name. 502It repeats this process until it comes up with a 503backup file that does not already exist or is not linked to the original file. 504.Pp 505You may also specify where you want the output to go with the 506.Fl o 507option; if that file already exists, it is backed up first. 508.Ss Notes For Patch Senders 509There are several things you should bear in mind if you are going to 510be sending out patches: 511.Pp 512First, you can save people a lot of grief by keeping a 513.Pa patchlevel.h 514file which is patched to increment the patch level as the first diff in the 515patch file you send out. 516If you put a 517.Qq Prereq: 518line in with the patch, it won't let them apply 519patches out of order without some warning. 520.Pp 521Second, make sure you've specified the file names right, either in a 522context diff header, or with an 523.Qq Index: 524line. 525If you are patching something in a subdirectory, be sure to tell the patch 526user to specify a 527.Fl p 528option as needed. 529.Pp 530Third, you can create a file by sending out a diff that compares a 531null file to the file you want to create. 532This will only work if the file you want to create doesn't exist already in 533the target directory. 534.Pp 535Fourth, take care not to send out reversed patches, since it makes people wonder 536whether they already applied the patch. 537.Pp 538Fifth, while you may be able to get away with putting 582 diff listings into 539one file, it is probably wiser to group related patches into separate files in 540case something goes haywire. 541.Sh ENVIRONMENT 542.Bl -tag -width "PATCH_VERSION_CONTROL" -compact 543.It Ev POSIXLY_CORRECT 544When set, 545.Nm 546behaves as if the 547.Fl Fl posix 548option has been specified. 549.It Ev SIMPLE_BACKUP_SUFFIX 550Extension to use for backup file names instead of 551.Qq .orig . 552.It Ev TMPDIR 553Directory to put temporary files in; default is 554.Pa /tmp . 555.It Ev PATCH_VERSION_CONTROL 556Selects when numbered backup files are made. 557.It Ev VERSION_CONTROL 558Same as 559.Ev PATCH_VERSION_CONTROL . 560.El 561.Sh FILES 562.Bl -tag -width "$TMPDIR/patch*" -compact 563.It Pa $TMPDIR/patch* 564.Nm 565temporary files 566.It Pa /dev/tty 567used to read input when 568.Nm 569prompts the user 570.El 571.Sh DIAGNOSTICS 572Too many to list here, but generally indicative that 573.Nm 574couldn't parse your patch file. 575.Pp 576The message 577.Qq Hmm... 578indicates that there is unprocessed text in the patch file and that 579.Nm 580is attempting to intuit whether there is a patch in that text and, if so, 581what kind of patch it is. 582.Pp 583The 584.Nm 585utility exits with one of the following values: 586.Pp 587.Bl -tag -width Ds -compact -offset indent 588.It \&0 589Successful completion. 590.It \&1 591One or more lines were written to a reject file. 592.It >\&1 593An error occurred. 594.El 595.Pp 596When applying a set of patches in a loop it behooves you to check this 597exit status so you don't apply a later patch to a partially patched file. 598.Sh SEE ALSO 599.Xr diff 1 600.Sh STANDARDS 601The 602.Nm 603utility is compliant with the 604.St -p1003.1-2004 605specification 606(except as detailed above for the 607.Fl -posix 608option), 609though the presence of 610.Nm 611itself is optional. 612.Pp 613The flags 614.Op Fl CEfstuvBFVxz 615and 616.Op Fl -posix 617are extensions to that specification. 618.Sh AUTHORS 619.An Larry Wall 620with many other contributors. 621.Sh CAVEATS 622.Nm 623cannot tell if the line numbers are off in an ed script, and can only detect 624bad line numbers in a normal diff when it finds a 625.Qq change 626or a 627.Qq delete 628command. 629A context diff using fuzz factor 3 may have the same problem. 630Until a suitable interactive interface is added, you should probably do 631a context diff in these cases to see if the changes made sense. 632Of course, compiling without errors is a pretty good indication that the patch 633worked, but not always. 634.Pp 635.Nm 636usually produces the correct results, even when it has to do a lot of 637guessing. 638However, the results are guaranteed to be correct only when the patch is 639applied to exactly the same version of the file that the patch was 640generated from. 641.Sh BUGS 642Could be smarter about partial matches, excessively deviant offsets and 643swapped code, but that would take an extra pass. 644.Pp 645Check patch mode 646.Pq Fl C 647will fail if you try to check several patches in succession that build on 648each other. 649The entire 650.Nm 651code would have to be restructured to keep temporary files around so that it 652can handle this situation. 653.Pp 654If code has been duplicated (for instance with #ifdef OLDCODE ... #else ... 655#endif), 656.Nm 657is incapable of patching both versions, and, if it works at all, will likely 658patch the wrong one, and tell you that it succeeded to boot. 659.Pp 660If you apply a patch you've already applied, 661.Nm 662will think it is a reversed patch, and offer to un-apply the patch. 663This could be construed as a feature. 664