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 1.26 2010/09/03 11:09:29 jmc Exp $ 23.\" $FreeBSD$ 24.Dd January 29, 2013 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 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 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'm 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 , 300.Fl Fl version-control Cm t | nil | never 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.El 332.It Fl v , Fl Fl version 333Causes 334.Nm 335to print out its revision header and patch level. 336.It Xo 337.Fl x Ar number , 338.Fl Fl debug Ar number 339.Xc 340Sets internal debugging flags, and is of interest only to 341.Nm 342patchers. 343.It Xo 344.Fl z Ar backup-ext , 345.Fl Fl suffix Ar backup-ext 346.Xc 347Causes the next argument to be interpreted as the backup extension, to be 348used in place of 349.Qq .orig . 350.It Fl Fl posix 351Enables strict 352.St -p1003.1-2008 353conformance, specifically: 354.Bl -enum 355.It 356Backup files are not created unless the 357.Fl b 358option is specified. 359.It 360If unspecified, the file name used is the first of the old, new and 361index files that exists. 362.El 363.El 364.Ss Patch Application 365.Nm 366will try to skip any leading garbage, apply the diff, 367and then skip any trailing garbage. 368Thus you could feed an article or message containing a 369diff listing to 370.Nm , 371and it should work. 372If the entire diff is indented by a consistent amount, 373this will be taken into account. 374.Pp 375With context diffs, and to a lesser extent with normal diffs, 376.Nm 377can detect when the line numbers mentioned in the patch are incorrect, 378and will attempt to find the correct place to apply each hunk of the patch. 379As a first guess, it takes the line number mentioned for the hunk, plus or 380minus any offset used in applying the previous hunk. 381If that is not the correct place, 382.Nm 383will scan both forwards and backwards for a set of lines matching the context 384given in the hunk. 385First 386.Nm 387looks for a place where all lines of the context match. 388If no such place is found, and it's a context diff, and the maximum fuzz factor 389is set to 1 or more, then another scan takes place ignoring the first and last 390line of context. 391If that fails, and the maximum fuzz factor is set to 2 or more, 392the first two and last two lines of context are ignored, 393and another scan is made. 394.Pq The default maximum fuzz factor is 2. 395.Pp 396If 397.Nm 398cannot find a place to install that hunk of the patch, it will put the hunk 399out to a reject file, which normally is the name of the output file plus 400.Qq .rej . 401(Note that the rejected hunk will come out in context diff form whether the 402input patch was a context diff or a normal diff. 403If the input was a normal diff, many of the contexts will simply be null.) 404The line numbers on the hunks in the reject file may be different than 405in the patch file: they reflect the approximate location patch thinks the 406failed hunks belong in the new file rather than the old one. 407.Pp 408As each hunk is completed, you will be told whether the hunk succeeded or 409failed, and which line (in the new file) 410.Nm 411thought the hunk should go on. 412If this is different from the line number specified in the diff, 413you will be told the offset. 414A single large offset MAY be an indication that a hunk was installed in the 415wrong place. 416You will also be told if a fuzz factor was used to make the match, in which 417case you should also be slightly suspicious. 418.Ss Filename Determination 419If no original file is specified on the command line, 420.Nm 421will try to figure out from the leading garbage what the name of the file 422to edit is. 423When checking a prospective file name, pathname components are stripped 424as specified by the 425.Fl p 426option and the file's existence and writability are checked relative 427to the current working directory (or the directory specified by the 428.Fl d 429option). 430.Pp 431If the diff is a context or unified diff, 432.Nm 433is able to determine the old and new file names from the diff header. 434For context diffs, 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 --- . 442For a unified diff, the 443.Dq old 444file is specified in the line beginning with 445.Qq --- 446and the 447.Dq new 448file is specified in the line beginning with 449.Qq +++ . 450If there is an 451.Qq Index: 452line in the leading garbage (regardless of the diff type), 453.Nm 454will use the file name from that line as the 455.Dq index 456file. 457.Pp 458.Nm 459will choose the file name by performing the following steps, with the first 460match used: 461.Bl -enum 462.It 463If 464.Nm 465is operating in strict 466.St -p1003.1-2008 467mode, the first of the 468.Dq old , 469.Dq new 470and 471.Dq index 472file names that exist is used. 473Otherwise, 474.Nm 475will examine either the 476.Dq old 477and 478.Dq new 479file names or, for a non-context diff, the 480.Dq index 481file name, and choose the file name with the fewest path components, 482the shortest basename, and the shortest total file name length (in that order). 483.It 484If no file exists, 485.Nm 486checks for the existence of the files in an SCCS or RCS directory 487(using the appropriate prefix or suffix) using the criteria specified 488above. 489If found, 490.Nm 491will attempt to get or check out the file. 492.It 493If no suitable file was found to patch, the patch file is a context or 494unified diff, and the old file was zero length, the new file name is 495created and used. 496.It 497If the file name still cannot be determined, 498.Nm 499will prompt the user for the file name to use. 500.El 501.Pp 502Additionally, if the leading garbage contains a 503.Qq Prereq:\ \& 504line, 505.Nm 506will take the first word from the prerequisites line (normally a version 507number) and check the input file to see if that word can be found. 508If not, 509.Nm 510will ask for confirmation before proceeding. 511.Pp 512The upshot of all this is that you should be able to say, while in a news 513interface, the following: 514.Pp 515.Dl | patch -d /usr/src/local/blurfl 516.Pp 517and patch a file in the blurfl directory directly from the article containing 518the patch. 519.Ss Backup Files 520By default, the patched version is put in place of the original, with 521the original file backed up to the same name with the extension 522.Qq .orig , 523or as specified by the 524.Fl B , 525.Fl V , 526or 527.Fl z 528options. 529The extension used for making backup files may also be specified in the 530.Ev SIMPLE_BACKUP_SUFFIX 531environment variable, which is overridden by the options above. 532.Pp 533If the backup file is a symbolic or hard link to the original file, 534.Nm 535creates a new backup file name by changing the first lowercase letter 536in the last component of the file's name into uppercase. 537If there are no more lowercase letters in the name, 538it removes the first character from the name. 539It repeats this process until it comes up with a 540backup file that does not already exist or is not linked to the original file. 541.Pp 542You may also specify where you want the output to go with the 543.Fl o 544option; if that file already exists, it is backed up first. 545.Ss Notes For Patch Senders 546There are several things you should bear in mind if you are going to 547be sending out patches: 548.Pp 549First, you can save people a lot of grief by keeping a 550.Pa patchlevel.h 551file which is patched to increment the patch level as the first diff in the 552patch file you send out. 553If you put a 554.Qq Prereq: 555line in with the patch, it will not let them apply 556patches out of order without some warning. 557.Pp 558Second, make sure you have specified the file names right, either in a 559context diff header, or with an 560.Qq Index: 561line. 562If you are patching something in a subdirectory, be sure to tell the patch 563user to specify a 564.Fl p 565option as needed. 566.Pp 567Third, you can create a file by sending out a diff that compares a 568null file to the file you want to create. 569This will only work if the file you want to create does not exist already in 570the target directory. 571.Pp 572Fourth, take care not to send out reversed patches, since it makes people wonder 573whether they already applied the patch. 574.Pp 575Fifth, while you may be able to get away with putting 582 diff listings into 576one file, it is probably wiser to group related patches into separate files in 577case something goes haywire. 578.Sh ENVIRONMENT 579.Bl -tag -width "PATCH_VERSION_CONTROL" -compact 580.It Ev POSIXLY_CORRECT 581When set, 582.Nm 583behaves as if the 584.Fl Fl posix 585option has been specified. 586.It Ev SIMPLE_BACKUP_SUFFIX 587Extension to use for backup file names instead of 588.Qq .orig . 589.It Ev TMPDIR 590Directory to put temporary files in; default is 591.Pa /tmp . 592.It Ev PATCH_VERSION_CONTROL 593Selects when numbered backup files are made. 594.It Ev VERSION_CONTROL 595Same as 596.Ev PATCH_VERSION_CONTROL . 597.El 598.Sh FILES 599.Bl -tag -width "$TMPDIR/patch*" -compact 600.It Pa $TMPDIR/patch* 601.Nm 602temporary files 603.It Pa /dev/tty 604used to read input when 605.Nm 606prompts the user 607.El 608.Sh EXIT STATUS 609The 610.Nm 611utility exits with one of the following values: 612.Pp 613.Bl -tag -width Ds -offset indent -compact 614.It 0 615Successful completion. 616.It 1 617One or more lines were written to a reject file. 618.It \*(Gt1 619An error occurred. 620.El 621.Pp 622When applying a set of patches in a loop it behooves you to check this 623exit status so you do not apply a later patch to a partially patched file. 624.Sh DIAGNOSTICS 625Too many to list here, but generally indicative that 626.Nm 627couldn't parse your patch file. 628.Pp 629The message 630.Qq Hmm... 631indicates that there is unprocessed text in the patch file and that 632.Nm 633is attempting to intuit whether there is a patch in that text and, if so, 634what kind of patch it is. 635.Sh SEE ALSO 636.Xr diff 1 637.Sh STANDARDS 638The 639.Nm 640utility is compliant with the 641.St -p1003.1-2008 642specification 643(except as detailed above for the 644.Fl -posix 645option), 646though the presence of 647.Nm 648itself is optional. 649.Pp 650The flags 651.Op Fl BCEFfstVvxz 652and 653.Op Fl -posix 654are extensions to that specification. 655.Sh AUTHORS 656.An Larry Wall 657with many other contributors. 658.Sh CAVEATS 659.Nm 660cannot tell if the line numbers are off in an ed script, and can only detect 661bad line numbers in a normal diff when it finds a 662.Qq change 663or a 664.Qq delete 665command. 666A context diff using fuzz factor 3 may have the same problem. 667Until a suitable interactive interface is added, you should probably do 668a context diff in these cases to see if the changes made sense. 669Of course, compiling without errors is a pretty good indication that the patch 670worked, but not always. 671.Pp 672.Nm 673usually produces the correct results, even when it has to do a lot of 674guessing. 675However, the results are guaranteed to be correct only when the patch is 676applied to exactly the same version of the file that the patch was 677generated from. 678.Sh BUGS 679Could be smarter about partial matches, excessively deviant offsets and 680swapped code, but that would take an extra pass. 681.Pp 682Check patch mode 683.Pq Fl C 684will fail if you try to check several patches in succession that build on 685each other. 686The entire 687.Nm 688code would have to be restructured to keep temporary files around so that it 689can handle this situation. 690.Pp 691If code has been duplicated (for instance with #ifdef OLDCODE ... #else ... 692#endif), 693.Nm 694is incapable of patching both versions, and, if it works at all, will likely 695patch the wrong one, and tell you that it succeeded to boot. 696.Pp 697If you apply a patch you have already applied, 698.Nm 699will think it is a reversed patch, and offer to un-apply the patch. 700This could be construed as a feature. 701