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 1.22 2023/06/16 11:27:00 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 June 16, 2023 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 backup-if-mismatch 45.Op Fl Fl no-backup-if-mismatch 46.Op Fl Fl posix 47.Op Ar origfile Op Ar patchfile 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 over-ruled 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 Fl B Ar backup-prefix , Fl Fl prefix Ar backup-prefix 91Causes the next argument to be interpreted as a prefix to the backup file 92name. 93If this argument is specified, any argument to 94.Fl z 95will be ignored. 96.It Fl b , Fl Fl backup 97Save a backup copy of the file before it is modified. 98By default the original file is saved with a backup extension of 99.Qq .orig 100unless the file already has a numbered backup, in which case a numbered 101backup is made. 102This is equivalent to specifying 103.Qo Fl V Cm existing Qc . 104This option is currently the default, unless 105.Fl Fl posix 106is specified. 107.It Fl Fl backup-if-mismatch 108Create a backup file if the patch doesn't apply cleanly. 109This option only makes sense when 110.Fl Fl backup 111is disabled, i.e. when in 112.Fl Fl posix 113mode. 114.It Fl C , Fl Fl check 115Checks that the patch would apply cleanly, but does not modify anything. 116.It Fl c , Fl Fl context 117Forces 118.Nm 119to interpret the patch file as a context diff. 120.It Fl D Ar symbol , Fl Fl ifdef Ar symbol 121Causes 122.Nm 123to use the 124.Qq #ifdef...#endif 125construct to mark changes. 126The argument following will be used as the differentiating symbol. 127Note that, unlike the C compiler, there must be a space between the 128.Fl D 129and the argument. 130.It Fl d Ar directory , Fl Fl directory Ar directory 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 Fl F Ar max-fuzz , Fl Fl fuzz Ar max-fuzz 147Sets the maximum fuzz factor. 148This option only applies to context diffs, and causes 149.Nm 150to ignore up to that many lines in looking for places to install a hunk. 151Note that a larger fuzz factor increases the odds of a faulty patch. 152The default fuzz factor is 2, and it may not be set to more than 153the number of lines of context in the context diff, ordinarily 3. 154.It Fl f , Fl Fl force 155Forces 156.Nm 157to assume that the user knows exactly what he or she is doing, and to not 158ask any questions. 159It assumes the following: 160skip patches for which a file to patch can't be found; 161patch files even though they have the wrong version for the 162.Qq Prereq: 163line in the patch; 164and assume that patches are not reversed even if they look like they are. 165This option does not suppress commentary; use 166.Fl s 167for that. 168.It Fl i Ar patchfile , Fl Fl input Ar patchfile 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 Fl Fl no-backup-if-mismatch 190Turn off 191.Fl Fl backup-if-mismatch . 192This option exists mostly for compatibility with GNU patch. 193.It Fl o Ar out-file , Fl Fl output Ar out-file 194Causes the next argument to be interpreted as the output file name. 195.It Fl p Ar strip-count , Fl Fl strip Ar strip-count 196Sets the pathname strip count, 197which controls how pathnames found in the patch file are treated, 198in case you keep your files in a different directory than the person who sent 199out the patch. 200The strip count specifies how many slashes are to be stripped from 201the front of the pathname. 202(Any intervening directory names also go away.) 203For example, supposing the file name in the patch file was 204.Pa /u/howard/src/blurfl/blurfl.c : 205.Pp 206Setting 207.Fl p Ns Ar 0 208gives the entire pathname unmodified. 209.Pp 210.Fl p Ns Ar 1 211gives 212.Pp 213.D1 Pa u/howard/src/blurfl/blurfl.c 214.Pp 215without the leading slash. 216.Pp 217.Fl p Ns Ar 4 218gives 219.Pp 220.D1 Pa blurfl/blurfl.c 221.Pp 222Not specifying 223.Fl p 224at all just gives you 225.Pa blurfl.c , 226unless all of the directories in the leading path 227.Pq Pa u/howard/src/blurfl 228exist and that path is relative, 229in which case you get the entire pathname unmodified. 230Whatever you end up with is looked for either in the current directory, 231or the directory specified by the 232.Fl d 233option. 234.It Fl R , Fl Fl reverse 235Tells 236.Nm 237that this patch was created with the old and new files swapped. 238(Yes, I'm afraid that does happen occasionally, human nature being what it 239is.) 240.Nm 241will attempt to swap each hunk around before applying it. 242Rejects will come out in the swapped format. 243The 244.Fl R 245option will not work with ed diff scripts because there is too little 246information to reconstruct the reverse operation. 247.Pp 248If the first hunk of a patch fails, 249.Nm 250will reverse the hunk to see if it can be applied that way. 251If it can, you will be asked if you want to have the 252.Fl R 253option set. 254If it can't, the patch will continue to be applied normally. 255(Note: this method cannot detect a reversed patch if it is a normal diff 256and if the first command is an append (i.e., it should have been a delete) 257since appends always succeed, due to the fact that a null context will match 258anywhere. 259Luckily, most patches add or change lines rather than delete them, so most 260reversed normal diffs will begin with a delete, which will fail, triggering 261the heuristic.) 262.It Fl r Ar rej-name , Fl Fl reject-file Ar rej-name 263Causes the next argument to be interpreted as the reject file name. 264.It Fl s , Fl Fl quiet , Fl Fl silent 265Makes 266.Nm 267do its work silently, unless an error occurs. 268.It Fl t , Fl Fl batch 269Similar to 270.Fl f , 271in that it suppresses questions, but makes some different assumptions: 272skip patches for which a file to patch can't be found (the same as 273.Fl f ) ; 274skip patches for which the file has the wrong version for the 275.Qq Prereq: 276line in the patch; 277and assume that patches are reversed if they look like they are. 278.It Fl u , Fl Fl unified 279Forces 280.Nm 281to interpret the patch file as a unified context diff (a unidiff). 282.It Fl V Cm t | nil | never | none , Fl Fl version-control Cm t | nil | never | none 283Causes the next argument to be interpreted as a method for creating 284backup file names. 285The type of backups made can also be given in the 286.Ev PATCH_VERSION_CONTROL 287or 288.Ev VERSION_CONTROL 289environment variables, which are overridden by this option. 290The 291.Fl B 292option overrides this option, causing the prefix to always be used for 293making backup file names. 294The values of the 295.Ev PATCH_VERSION_CONTROL 296and 297.Ev VERSION_CONTROL 298environment variables and the argument to the 299.Fl V 300option are like the GNU Emacs 301.Dq version-control 302variable; they also recognize synonyms that are more descriptive. 303The valid values are (unique abbreviations are accepted): 304.Bl -tag -width Ds -offset indent 305.It Cm t , numbered 306Always make numbered backups. 307.It Cm nil , existing 308Make numbered backups of files that already have them, 309simple backups of the others. 310.It Cm never , simple 311Always make simple backups. 312.It Cm none 313No backups are created. 314.El 315.It Fl v , Fl Fl version 316Causes 317.Nm 318to print out its revision header and patch level. 319.It Fl x Ar number , Fl Fl debug Ar number 320Sets internal debugging flags, and is of interest only to 321.Nm 322patchers. 323.It Fl z Ar backup-ext , Fl Fl suffix Ar backup-ext 324Causes the next argument to be interpreted as the backup extension, to be 325used in place of 326.Qq .orig . 327.It Fl Fl posix 328Enables strict 329.St -p1003.1-2004 330conformance, specifically: 331.Bl -enum 332.It 333Backup files are not created unless the 334.Fl b 335option is specified. 336.It 337If unspecified, the file name used is the first of the old, new and 338index files that exists. 339.El 340.El 341.Ss Patch Application 342.Nm 343will try to skip any leading garbage, apply the diff, 344and then skip any trailing garbage. 345Thus you could feed an article or message containing a 346diff listing to 347.Nm , 348and it should work. 349If the entire diff is indented by a consistent amount, 350this will be taken into account. 351.Pp 352With context diffs, and to a lesser extent with normal diffs, 353.Nm 354can detect when the line numbers mentioned in the patch are incorrect, 355and will attempt to find the correct place to apply each hunk of the patch. 356As a first guess, it takes the line number mentioned for the hunk, plus or 357minus any offset used in applying the previous hunk. 358If that is not the correct place, 359.Nm 360will scan both forwards and backwards for a set of lines matching the context 361given in the hunk. 362First 363.Nm 364looks for a place where all lines of the context match. 365If no such place is found, and it's a context diff, and the maximum fuzz factor 366is set to 1 or more, then another scan takes place ignoring the first and last 367line of context. 368If that fails, and the maximum fuzz factor is set to 2 or more, 369the first two and last two lines of context are ignored, 370and another scan is made. 371.Pq The default maximum fuzz factor is 2. 372.Pp 373If 374.Nm 375cannot find a place to install that hunk of the patch, it will put the hunk 376out to a reject file, which normally is the name of the output file plus 377.Qq .rej . 378(Note that the rejected hunk will come out in context diff form whether the 379input patch was a context diff or a normal diff. 380If the input was a normal diff, many of the contexts will simply be null.) 381The line numbers on the hunks in the reject file may be different than 382in the patch file: they reflect the approximate location patch thinks the 383failed hunks belong in the new file rather than the old one. 384.Pp 385As each hunk is completed, you will be told whether the hunk succeeded or 386failed, and which line (in the new file) 387.Nm 388thought the hunk should go on. 389If this is different from the line number specified in the diff, 390you will be told the offset. 391A single large offset MAY be an indication that a hunk was installed in the 392wrong place. 393You will also be told if a fuzz factor was used to make the match, in which 394case you should also be slightly suspicious. 395.Ss Filename Determination 396If no original file is specified on the command line, 397.Nm 398will try to figure out from the leading garbage what the name of the file 399to edit is. 400When checking a prospective file name, pathname components are stripped 401as specified by the 402.Fl p 403option and the file's existence and writability are checked relative 404to the current working directory (or the directory specified by the 405.Fl d 406option). 407.Pp 408If the diff is a context or unified diff, 409.Nm 410is able to determine the old and new file names from the diff header. 411For context diffs, the 412.Dq old 413file is specified in the line beginning with 414.Qq *** 415and the 416.Dq new 417file is specified in the line beginning with 418.Qq --- . 419For a unified diff, the 420.Dq old 421file is specified in the line beginning with 422.Qq --- 423and the 424.Dq new 425file is specified in the line beginning with 426.Qq +++ . 427If there is an 428.Qq Index: 429line in the leading garbage (regardless of the diff type), 430.Nm 431will use the file name from that line as the 432.Dq index 433file. 434.Pp 435.Nm 436will choose the file name by performing the following steps, with the first 437match used: 438.Bl -enum 439.It 440If 441.Nm 442is operating in strict 443.St -p1003.1-2004 444mode, the first of the 445.Dq old , 446.Dq new 447and 448.Dq index 449file names that exist is used. 450Otherwise, 451.Nm 452will examine either the 453.Dq old 454and 455.Dq new 456file names or, for a non-context diff, the 457.Dq index 458file name, and choose the file name with the fewest path components, 459the shortest basename, and the shortest total file name length (in that order). 460.It 461If no file exists, 462.Nm 463checks for the existence of the files in an RCS directory using the criteria 464specified above. 465If found, 466.Nm 467will attempt to get or check out the file. 468.It 469If no suitable file was found to patch, the patch file is a context or 470unified diff, and the old file was zero length, the new file name is 471created and used. 472.It 473If the file name still cannot be determined, 474.Nm 475will prompt the user for the file name to use. 476.El 477.Pp 478Additionally, if the leading garbage contains a 479.Qq Prereq:\ \& 480line, 481.Nm 482will take the first word from the prerequisites line (normally a version 483number) and check the input file to see if that word can be found. 484If not, 485.Nm 486will ask for confirmation before proceeding. 487.Pp 488The upshot of all this is that you should be able to say, while in a news 489interface, the following: 490.Pp 491.Dl | patch -d /usr/src/local/blurfl 492.Pp 493and patch a file in the blurfl directory directly from the article containing 494the patch. 495.Ss Backup Files 496By default, the patched version is put in place of the original, with 497the original file backed up to the same name with the extension 498.Qq .orig , 499or as specified by the 500.Fl B , 501.Fl V , 502or 503.Fl z 504options. 505The extension used for making backup files may also be specified in the 506.Ev SIMPLE_BACKUP_SUFFIX 507environment variable, which is overridden by the options above. 508.Pp 509If the backup file is a symbolic or hard link to the original file, 510.Nm 511creates a new backup file name by changing the first lowercase letter 512in the last component of the file's name into uppercase. 513If there are no more lowercase letters in the name, 514it removes the first character from the name. 515It repeats this process until it comes up with a 516backup file that does not already exist or is not linked to the original file. 517.Pp 518You may also specify where you want the output to go with the 519.Fl o 520option; if that file already exists, it is backed up first. 521.Ss Notes For Patch Senders 522There are several things you should bear in mind if you are going to 523be sending out patches: 524.Pp 525First, you can save people a lot of grief by keeping a 526.Pa patchlevel.h 527file which is patched to increment the patch level as the first diff in the 528patch file you send out. 529If you put a 530.Qq Prereq: 531line in with the patch, it won't let them apply 532patches out of order without some warning. 533.Pp 534Second, make sure you've specified the file names right, either in a 535context diff header, or with an 536.Qq Index: 537line. 538If you are patching something in a subdirectory, be sure to tell the patch 539user to specify a 540.Fl p 541option as needed. 542.Pp 543Third, you can create a file by sending out a diff that compares a 544null file to the file you want to create. 545This will only work if the file you want to create doesn't exist already in 546the target directory. 547.Pp 548Fourth, take care not to send out reversed patches, since it makes people wonder 549whether they already applied the patch. 550.Pp 551Fifth, while you may be able to get away with putting 582 diff listings into 552one file, it is probably wiser to group related patches into separate files in 553case something goes haywire. 554.Sh ENVIRONMENT 555.Bl -tag -width "PATCH_VERSION_CONTROL" -compact 556.It Ev POSIXLY_CORRECT 557When set, 558.Nm 559behaves as if the 560.Fl Fl posix 561option has been specified. 562.It Ev SIMPLE_BACKUP_SUFFIX 563Extension to use for backup file names instead of 564.Qq .orig . 565.It Ev TMPDIR 566Directory to put temporary files in; default is 567.Pa /tmp . 568.It Ev PATCH_VERSION_CONTROL 569Selects when numbered backup files are made. 570.It Ev VERSION_CONTROL 571Same as 572.Ev PATCH_VERSION_CONTROL . 573.El 574.Sh FILES 575.Bl -tag -width "$TMPDIR/patch*" -compact 576.It Pa $TMPDIR/patch* 577.Nm 578temporary files 579.It Pa /dev/tty 580used to read input when 581.Nm 582prompts the user 583.El 584.Sh DIAGNOSTICS 585Too many to list here, but generally indicative that 586.Nm 587couldn't parse your patch file. 588.Pp 589The message 590.Qq Hmm... 591indicates that there is unprocessed text in the patch file and that 592.Nm 593is attempting to intuit whether there is a patch in that text and, if so, 594what kind of patch it is. 595.Pp 596The 597.Nm 598utility exits with one of the following values: 599.Pp 600.Bl -tag -width Ds -compact -offset indent 601.It \&0 602Successful completion. 603.It \&1 604One or more lines were written to a reject file. 605.It >\&1 606An error occurred. 607.El 608.Pp 609When applying a set of patches in a loop it behooves you to check this 610exit status so you don't apply a later patch to a partially patched file. 611.Sh SEE ALSO 612.Xr diff 1 613.Sh STANDARDS 614The 615.Nm 616utility is compliant with the 617.St -p1003.1-2004 618specification 619(except as detailed above for the 620.Fl Fl posix 621option), 622though the presence of 623.Nm 624itself is optional. 625.Pp 626The flags 627.Op Fl CEfstuvBFVxz 628and 629.Op Fl Fl posix 630are extensions to that specification. 631.Sh AUTHORS 632.An Larry Wall 633with many other contributors. 634.Sh CAVEATS 635.Nm 636cannot tell if the line numbers are off in an ed script, and can only detect 637bad line numbers in a normal diff when it finds a 638.Qq change 639or a 640.Qq delete 641command. 642A context diff using fuzz factor 3 may have the same problem. 643Until a suitable interactive interface is added, you should probably do 644a context diff in these cases to see if the changes made sense. 645Of course, compiling without errors is a pretty good indication that the patch 646worked, but not always. 647.Pp 648.Nm 649usually produces the correct results, even when it has to do a lot of 650guessing. 651However, the results are guaranteed to be correct only when the patch is 652applied to exactly the same version of the file that the patch was 653generated from. 654.Sh BUGS 655Could be smarter about partial matches, excessively deviant offsets and 656swapped code, but that would take an extra pass. 657.Pp 658Check patch mode 659.Pq Fl C 660will fail if you try to check several patches in succession that build on 661each other. 662The entire 663.Nm 664code would have to be restructured to keep temporary files around so that it 665can handle this situation. 666.Pp 667If code has been duplicated (for instance with #ifdef OLDCODE ... #else ... 668#endif), 669.Nm 670is incapable of patching both versions, and, if it works at all, will likely 671patch the wrong one, and tell you that it succeeded to boot. 672.Pp 673If you apply a patch you've already applied, 674.Nm 675will think it is a reversed patch, and offer to un-apply the patch. 676This could be construed as a feature. 677