1.\"- 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.\" $OpenBSD: patch.1,v 1.27 2014/04/15 06:26:54 jmc Exp $ 23.\" $FreeBSD$ 24.Dd November 3, 2019 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.Bk -words 33.Op Fl bCcEeflNnRstuv 34.Op Fl B Ar backup-prefix 35.Op Fl D Ar symbol 36.Op Fl d Ar directory 37.Op Fl F Ar max-fuzz 38.Op Fl i Ar patchfile 39.Op Fl o Ar out-file 40.Op Fl p Ar strip-count 41.Op Fl r Ar rej-name 42.Op Fl V Cm t | nil | never | none 43.Op Fl x Ar number 44.Op Fl z Ar backup-ext 45.Op Fl Fl posix 46.Op Ar origfile Op Ar patchfile 47.Ek 48.Nm 49.Pf \*(Lt Ar patchfile 50.Sh DESCRIPTION 51.Nm 52will take a patch file containing any of the four forms of difference 53listing produced by the 54.Xr diff 1 55program and apply those differences to an original file, 56producing a patched version. 57If 58.Ar patchfile 59is omitted, or is a hyphen, the patch will be read from the standard input. 60.Pp 61.Nm 62will attempt to determine the type of the diff listing, unless overruled by a 63.Fl c , 64.Fl e , 65.Fl n , 66or 67.Fl u 68option. 69Context diffs (old-style, new-style, and unified) and 70normal diffs are applied directly by the 71.Nm 72program itself, whereas ed diffs are simply fed to the 73.Xr ed 1 74editor via a pipe. 75.Pp 76If the 77.Ar patchfile 78contains more than one patch, 79.Nm 80will try to apply each of them as if they came from separate patch files. 81This means, among other things, that it is assumed that the name of the file 82to patch must be determined for each diff listing, and that the garbage before 83each diff listing will be examined for interesting things such as file names 84and revision level (see the section on 85.Sx Filename Determination 86below). 87.Pp 88The options are as follows: 89.Bl -tag -width Ds 90.It Xo 91.Fl B Ar backup-prefix , 92.Fl Fl prefix Ar backup-prefix 93.Xc 94Causes the next argument to be interpreted as a prefix to the backup file 95name. 96If this argument is specified, any argument to 97.Fl z 98will be ignored. 99.It Fl b , Fl Fl backup 100Save a backup copy of the file before it is modified. 101By default the original file is saved with a backup extension of 102.Qq .orig 103unless the file already has a numbered backup, in which case a numbered 104backup is made. 105This is equivalent to specifying 106.Qo Fl V Cm existing Qc . 107This option is currently the default, unless 108.Fl -posix 109is specified. 110.It Fl C , Fl Fl check , Fl Fl dry-run 111Checks that the patch would apply cleanly, but does not modify anything. 112.It Fl c , Fl Fl context 113Forces 114.Nm 115to interpret the patch file as a context diff. 116.It Xo 117.Fl D Ar symbol , 118.Fl Fl ifdef Ar symbol 119.Xc 120Causes 121.Nm 122to use the 123.Qq #ifdef...#endif 124construct to mark changes. 125The argument following will be used as the differentiating symbol. 126Note that, unlike the C compiler, there must be a space between the 127.Fl D 128and the argument. 129.It Xo 130.Fl d Ar directory , 131.Fl Fl directory Ar directory 132.Xc 133Causes 134.Nm 135to interpret the next argument as a directory, 136and change the working directory to it before doing anything else. 137.It Fl E , Fl Fl remove-empty-files 138Causes 139.Nm 140to remove output files that are empty after the patches have been applied. 141This option is useful when applying patches that create or remove files. 142.It Fl e , Fl Fl ed 143Forces 144.Nm 145to interpret the patch file as an 146.Xr ed 1 147script. 148.It Xo 149.Fl F Ar max-fuzz , 150.Fl Fl fuzz Ar max-fuzz 151.Xc 152Sets the maximum fuzz factor. 153This option only applies to context diffs, and causes 154.Nm 155to ignore up to that many lines in looking for places to install a hunk. 156Note that a larger fuzz factor increases the odds of a faulty patch. 157The default fuzz factor is 2, and it may not be set to more than 158the number of lines of context in the context diff, ordinarily 3. 159.It Fl f , Fl Fl force 160Forces 161.Nm 162to assume that the user knows exactly what he or she is doing, and to not 163ask any questions. 164It assumes the following: 165skip patches for which a file to patch cannot be found; 166patch files even though they have the wrong version for the 167.Qq Prereq : 168line in the patch; 169and assume that patches are not reversed even if they look like they are. 170This option does not suppress commentary; use 171.Fl s 172for that. 173.It Xo 174.Fl i Ar patchfile , 175.Fl Fl input Ar patchfile 176.Xc 177Causes the next argument to be interpreted as the input file name 178(i.e., a patchfile). 179This option may be specified multiple times. 180.It Fl l , Fl Fl ignore-whitespace 181Causes the pattern matching to be done loosely, in case the tabs and 182spaces have been munged in your input file. 183Any sequence of whitespace in the pattern line will match any sequence 184in the input file. 185Normal characters must still match exactly. 186Each line of the context must still match a line in the input file. 187.It Fl N , Fl Fl forward 188Causes 189.Nm 190to ignore patches that it thinks are reversed or already applied. 191See also 192.Fl R . 193.It Fl n , Fl Fl normal 194Forces 195.Nm 196to interpret the patch file as a normal diff. 197.It Xo 198.Fl o Ar out-file , 199.Fl Fl output Ar out-file 200.Xc 201Causes the next argument to be interpreted as the output file name. 202.It Xo 203.Fl p Ar strip-count , 204.Fl Fl strip Ar strip-count 205.Xc 206Sets the pathname strip count, 207which controls how pathnames found in the patch file are treated, 208in case you keep your files in a different directory than the person who sent 209out the patch. 210The strip count specifies how many slashes are to be stripped from 211the front of the pathname. 212(Any intervening directory names also go away.) 213For example, supposing the file name in the patch file was 214.Pa /u/howard/src/blurfl/blurfl.c : 215.Pp 216Setting 217.Fl p Ns Ar 0 218gives the entire pathname unmodified. 219.Pp 220.Fl p Ns Ar 1 221gives 222.Pp 223.D1 Pa u/howard/src/blurfl/blurfl.c 224.Pp 225without the leading slash. 226.Pp 227.Fl p Ns Ar 4 228gives 229.Pp 230.D1 Pa blurfl/blurfl.c 231.Pp 232Not specifying 233.Fl p 234at all just gives you 235.Pa blurfl.c , 236unless all of the directories in the leading path 237.Pq Pa u/howard/src/blurfl 238exist and that path is relative, 239in which case you get the entire pathname unmodified. 240Whatever you end up with is looked for either in the current directory, 241or the directory specified by the 242.Fl d 243option. 244.It Fl R , Fl Fl reverse 245Tells 246.Nm 247that this patch was created with the old and new files swapped. 248(Yes, I am afraid that does happen occasionally, human nature being what it 249is.) 250.Nm 251will attempt to swap each hunk around before applying it. 252Rejects will come out in the swapped format. 253The 254.Fl R 255option will not work with ed diff scripts because there is too little 256information to reconstruct the reverse operation. 257.Pp 258If the first hunk of a patch fails, 259.Nm 260will reverse the hunk to see if it can be applied that way. 261If it can, you will be asked if you want to have the 262.Fl R 263option set. 264If it cannot, the patch will continue to be applied normally. 265(Note: this method cannot detect a reversed patch if it is a normal diff 266and if the first command is an append (i.e., it should have been a delete) 267since appends always succeed, due to the fact that a null context will match 268anywhere. 269Luckily, most patches add or change lines rather than delete them, so most 270reversed normal diffs will begin with a delete, which will fail, triggering 271the heuristic.) 272.It Xo 273.Fl r Ar rej-name , 274.Fl Fl reject-file Ar rej-name 275.Xc 276Causes the next argument to be interpreted as the reject file name. 277.It Xo 278.Fl s , Fl Fl quiet , 279.Fl Fl silent 280.Xc 281Makes 282.Nm 283do its work silently, unless an error occurs. 284.It Fl t , Fl Fl batch 285Similar to 286.Fl f , 287in that it suppresses questions, but makes some different assumptions: 288skip patches for which a file to patch cannot be found (the same as 289.Fl f ) ; 290skip patches for which the file has the wrong version for the 291.Qq Prereq : 292line in the patch; 293and assume that patches are reversed if they look like they are. 294.It Fl u , Fl Fl unified 295Forces 296.Nm 297to interpret the patch file as a unified context diff (a unidiff). 298.It Xo 299.Fl V Cm t | nil | never | none , 300.Fl Fl version-control Cm t | nil | never | none 301.Xc 302Causes the next argument to be interpreted as a method for creating 303backup file names. 304The type of backups made can also be given in the 305.Ev PATCH_VERSION_CONTROL 306or 307.Ev VERSION_CONTROL 308environment variables, which are overridden by this option. 309The 310.Fl B 311option overrides this option, causing the prefix to always be used for 312making backup file names. 313The values of the 314.Ev PATCH_VERSION_CONTROL 315and 316.Ev VERSION_CONTROL 317environment variables and the argument to the 318.Fl V 319option are like the GNU Emacs 320.Dq version-control 321variable; they also recognize synonyms that are more descriptive. 322The valid values are (unique abbreviations are accepted): 323.Bl -tag -width Ds -offset indent 324.It Cm t , numbered 325Always make numbered backups. 326.It Cm nil , existing 327Make numbered backups of files that already have them, 328simple backups of the others. 329.It Cm never , simple 330Always make simple backups. 331.It Cm none 332Do not make backups. 333.El 334.It Fl v , Fl Fl version 335Causes 336.Nm 337to print out its revision header and patch level. 338.It Xo 339.Fl x Ar number , 340.Fl Fl debug Ar number 341.Xc 342Sets internal debugging flags, and is of interest only to 343.Nm 344patchers. 345.It Xo 346.Fl z Ar backup-ext , 347.Fl Fl suffix Ar backup-ext 348.Xc 349Causes the next argument to be interpreted as the backup extension, to be 350used in place of 351.Qq .orig . 352.It Fl Fl posix 353Enables strict 354.St -p1003.1-2008 355conformance, specifically: 356.Bl -enum 357.It 358Backup files are not created unless the 359.Fl b 360option is specified. 361.It 362If unspecified, the file name used is the first of the old, new and 363index files that exists. 364.El 365.El 366.Ss Patch Application 367.Nm 368will try to skip any leading garbage, apply the diff, 369and then skip any trailing garbage. 370Thus you could feed an article or message containing a 371diff listing to 372.Nm , 373and it should work. 374If the entire diff is indented by a consistent amount, 375this will be taken into account. 376.Pp 377With context diffs, and to a lesser extent with normal diffs, 378.Nm 379can detect when the line numbers mentioned in the patch are incorrect, 380and will attempt to find the correct place to apply each hunk of the patch. 381As a first guess, it takes the line number mentioned for the hunk, plus or 382minus any offset used in applying the previous hunk. 383If that is not the correct place, 384.Nm 385will scan both forwards and backwards for a set of lines matching the context 386given in the hunk. 387First 388.Nm 389looks for a place where all lines of the context match. 390If no such place is found, and it is a context diff, and the maximum fuzz factor 391is set to 1 or more, then another scan takes place ignoring the first and last 392line of context. 393If that fails, and the maximum fuzz factor is set to 2 or more, 394the first two and last two lines of context are ignored, 395and another scan is made. 396.Pq The default maximum fuzz factor is 2 . 397.Pp 398If 399.Nm 400cannot find a place to install that hunk of the patch, it will put the hunk 401out to a reject file, which normally is the name of the output file plus 402.Qq .rej . 403(Note that the rejected hunk will come out in context diff form whether the 404input patch was a context diff or a normal diff. 405If the input was a normal diff, many of the contexts will simply be null.) 406The line numbers on the hunks in the reject file may be different than 407in the patch file: they reflect the approximate location patch thinks the 408failed hunks belong in the new file rather than the old one. 409.Pp 410As each hunk is completed, you will be told whether the hunk succeeded or 411failed, and which line (in the new file) 412.Nm 413thought the hunk should go on. 414If this is different from the line number specified in the diff, 415you will be told the offset. 416A single large offset MAY be an indication that a hunk was installed in the 417wrong place. 418You will also be told if a fuzz factor was used to make the match, in which 419case you should also be slightly suspicious. 420.Ss Filename Determination 421If no original file is specified on the command line, 422.Nm 423will try to figure out from the leading garbage what the name of the file 424to edit is. 425When checking a prospective file name, pathname components are stripped 426as specified by the 427.Fl p 428option and the file's existence and writability are checked relative 429to the current working directory (or the directory specified by the 430.Fl d 431option). 432.Pp 433If the diff is a context or unified diff, 434.Nm 435is able to determine the old and new file names from the diff header. 436For context diffs, the 437.Dq old 438file is specified in the line beginning with 439.Qq *** 440and the 441.Dq new 442file is specified in the line beginning with 443.Qq --- . 444For a unified diff, the 445.Dq old 446file is specified in the line beginning with 447.Qq --- 448and the 449.Dq new 450file is specified in the line beginning with 451.Qq +++ . 452If there is an 453.Qq Index : 454line in the leading garbage (regardless of the diff type), 455.Nm 456will use the file name from that line as the 457.Dq index 458file. 459.Pp 460.Nm 461will choose the file name by performing the following steps, with the first 462match used: 463.Bl -enum 464.It 465If 466.Nm 467is operating in strict 468.St -p1003.1-2008 469mode, the first of the 470.Dq old , 471.Dq new 472and 473.Dq index 474file names that exist is used. 475Otherwise, 476.Nm 477will examine either the 478.Dq old 479and 480.Dq new 481file names or, for a non-context diff, the 482.Dq index 483file name, and choose the file name with the fewest path components, 484the shortest basename, and the shortest total file name length (in that order). 485.It 486If no suitable file was found to patch, the patch file is a context or 487unified diff, and the old file was zero length, the new file name is 488created and used. 489.It 490If the file name still cannot be determined, 491.Nm 492will prompt the user for the file name to use. 493.El 494.Pp 495Additionally, if the leading garbage contains a 496.Qq Prereq:\ \& 497line, 498.Nm 499will take the first word from the prerequisites line (normally a version 500number) and check the input file to see if that word can be found. 501If not, 502.Nm 503will ask for confirmation before proceeding. 504.Pp 505The upshot of all this is that you should be able to say, while in a news 506interface, the following: 507.Pp 508.Dl | patch -d /usr/src/local/blurfl 509.Pp 510and patch a file in the blurfl directory directly from the article containing 511the patch. 512.Ss Backup Files 513By default, the patched version is put in place of the original, with 514the original file backed up to the same name with the extension 515.Qq .orig , 516or as specified by the 517.Fl B , 518.Fl V , 519or 520.Fl z 521options. 522The extension used for making backup files may also be specified in the 523.Ev SIMPLE_BACKUP_SUFFIX 524environment variable, which is overridden by the options above. 525.Pp 526If the backup file is a symbolic or hard link to the original file, 527.Nm 528creates a new backup file name by changing the first lowercase letter 529in the last component of the file's name into uppercase. 530If there are no more lowercase letters in the name, 531it removes the first character from the name. 532It repeats this process until it comes up with a 533backup file that does not already exist or is not linked to the original file. 534.Pp 535You may also specify where you want the output to go with the 536.Fl o 537option; if that file already exists, it is backed up first. 538.Ss Notes For Patch Senders 539There are several things you should bear in mind if you are going to 540be sending out patches: 541.Pp 542First, you can save people a lot of grief by keeping a 543.Pa patchlevel.h 544file which is patched to increment the patch level as the first diff in the 545patch file you send out. 546If you put a 547.Qq Prereq : 548line in with the patch, it will not let them apply 549patches out of order without some warning. 550.Pp 551Second, make sure you have specified the file names right, either in a 552context diff header, or with an 553.Qq Index : 554line. 555If you are patching something in a subdirectory, be sure to tell the patch 556user to specify a 557.Fl p 558option as needed. 559.Pp 560Third, you can create a file by sending out a diff that compares a 561null file to the file you want to create. 562If the file you want to create already exists in the target directory when the 563diff is applied, then 564.Nm 565will identify the patch as potentially reversed and offer to reverse the patch. 566.Pp 567Fourth, take care not to send out reversed patches, since it makes people wonder 568whether they already applied the patch. 569.Pp 570Fifth, while you may be able to get away with putting 582 diff listings into 571one file, it is probably wiser to group related patches into separate files in 572case something goes haywire. 573.Sh ENVIRONMENT 574.Bl -tag -width "PATCH_VERSION_CONTROL" -compact 575.It Ev POSIXLY_CORRECT 576When set, 577.Nm 578behaves as if the 579.Fl Fl posix 580option has been specified. 581.It Ev SIMPLE_BACKUP_SUFFIX 582Extension to use for backup file names instead of 583.Qq .orig . 584.It Ev TMPDIR 585Directory to put temporary files in; default is 586.Pa /tmp . 587.It Ev PATCH_VERSION_CONTROL 588Selects when numbered backup files are made. 589.It Ev VERSION_CONTROL 590Same as 591.Ev PATCH_VERSION_CONTROL . 592.El 593.Sh FILES 594.Bl -tag -width "$TMPDIR/patch*" -compact 595.It Pa $TMPDIR/patch* 596.Nm 597temporary files 598.It Pa /dev/tty 599used to read input when 600.Nm 601prompts the user 602.El 603.Sh EXIT STATUS 604The 605.Nm 606utility exits with one of the following values: 607.Pp 608.Bl -tag -width Ds -offset indent -compact 609.It 0 610Successful completion. 611.It 1 612One or more lines were written to a reject file. 613.It \*(Gt1 614An error occurred. 615.El 616.Pp 617When applying a set of patches in a loop it behooves you to check this 618exit status so you do not apply a later patch to a partially patched file. 619.Sh DIAGNOSTICS 620Too many to list here, but generally indicative that 621.Nm 622couldn't parse your patch file. 623.Pp 624The message 625.Qq Hmm... 626indicates that there is unprocessed text in the patch file and that 627.Nm 628is attempting to intuit whether there is a patch in that text and, if so, 629what kind of patch it is. 630.Sh SEE ALSO 631.Xr diff 1 632.Sh STANDARDS 633The 634.Nm 635utility is compliant with the 636.St -p1003.1-2008 637specification, 638except as detailed above for the 639.Fl -posix 640option. 641.Pp 642The flags 643.Op Fl BCEFfstVvxz 644and 645.Op Fl -posix 646are extensions to that specification. 647.Sh AUTHORS 648.An Larry Wall 649with many other contributors. 650.Sh CAVEATS 651.Nm 652cannot tell if the line numbers are off in an ed script, and can only detect 653bad line numbers in a normal diff when it finds a 654.Qq change 655or a 656.Qq delete 657command. 658A context diff using fuzz factor 3 may have the same problem. 659Until a suitable interactive interface is added, you should probably do 660a context diff in these cases to see if the changes made sense. 661Of course, compiling without errors is a pretty good indication that the patch 662worked, but not always. 663.Pp 664.Nm 665usually produces the correct results, even when it has to do a lot of 666guessing. 667However, the results are guaranteed to be correct only when the patch is 668applied to exactly the same version of the file that the patch was 669generated from. 670.Sh BUGS 671Could be smarter about partial matches, excessively deviant offsets and 672swapped code, but that would take an extra pass. 673.Pp 674Check patch mode 675.Pq Fl C 676will fail if you try to check several patches in succession that build on 677each other. 678The entire 679.Nm 680code would have to be restructured to keep temporary files around so that it 681can handle this situation. 682.Pp 683If code has been duplicated (for instance with #ifdef OLDCODE ... #else ... 684#endif), 685.Nm 686is incapable of patching both versions, and, if it works at all, will likely 687patch the wrong one, and tell you that it succeeded to boot. 688.Pp 689If you apply a patch you have already applied, 690.Nm 691will think it is a reversed patch, and offer to un-apply the patch. 692This could be construed as a feature. 693