1.\" $OpenBSD: patch.1,v 1.18 2007/04/18 21:52:24 sobrado 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 July 23, 2003 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 patch 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 patch 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 but that will change in a future release. 106.It Fl C , Fl Fl check 107Checks that the patch would apply cleanly, but does not modify anything. 108.It Fl c , Fl Fl context 109Forces 110.Nm 111to interpret the patch file as a context diff. 112.It Xo 113.Fl D Ar symbol , 114.Fl Fl ifdef Ar symbol 115.Xc 116Causes 117.Nm 118to use the 119.Qq #ifdef...#endif 120construct to mark changes. 121The argument following will be used as the differentiating symbol. 122Note that, unlike the C compiler, there must be a space between the 123.Fl D 124and the argument. 125.It Xo 126.Fl d Ar directory , 127.Fl Fl directory Ar directory 128.Xc 129Causes 130.Nm 131to interpret the next argument as a directory, and 132.Xr cd 1 133to it before doing anything else. 134.It Fl E , Fl Fl remove-empty-files 135Causes 136.Nm 137to remove output files that are empty after the patches have been applied. 138This option is useful when applying patches that create or remove files. 139.It Fl e , Fl Fl ed 140Forces 141.Nm 142to interpret the patch file as an 143.Xr ed 1 144script. 145.It Xo 146.Fl F Ar max-fuzz , 147.Fl Fl fuzz Ar max-fuzz 148.Xc 149Sets the maximum fuzz factor. 150This option only applies to context diffs, and causes 151.Nm 152to ignore up to that many lines in looking for places to install a hunk. 153Note that a larger fuzz factor increases the odds of a faulty patch. 154The default fuzz factor is 2, and it may not be set to more than 155the number of lines of context in the context diff, ordinarily 3. 156.It Fl f , Fl Fl force 157Forces 158.Nm 159to assume that the user knows exactly what he or she is doing, and to not 160ask any questions. 161It assumes the following: 162skip patches for which a file to patch can't be found; 163patch files even though they have the wrong version for the 164.Qq Prereq: 165line in the patch; 166and assume that patches are not reversed even if they look like they are. 167This option does not suppress commentary; use 168.Fl s 169for that. 170.It Xo 171.Fl i Ar patchfile , 172.Fl Fl input Ar patchfile 173.Xc 174Causes the next argument to be interpreted as the input file name 175(i.e. a patchfile). 176This option may be specified multiple times. 177.It Fl l , Fl Fl ignore-whitespace 178Causes the pattern matching to be done loosely, in case the tabs and 179spaces have been munged in your input file. 180Any sequence of whitespace in the pattern line will match any sequence 181in the input file. 182Normal characters must still match exactly. 183Each line of the context must still match a line in the input file. 184.It Fl N , Fl Fl forward 185Causes 186.Nm 187to ignore patches that it thinks are reversed or already applied. 188See also 189.Fl R . 190.It Fl n , Fl Fl normal 191Forces 192.Nm 193to interpret the patch file as a normal diff. 194.It Xo 195.Fl o Ar out-file , 196.Fl Fl output Ar out-file 197.Xc 198Causes the next argument to be interpreted as the output file name. 199.It Xo 200.Fl p Ar strip-count , 201.Fl Fl strip Ar strip-count 202.Xc 203Sets the pathname strip count, 204which controls how pathnames found in the patch file are treated, 205in case you keep your files in a different directory than the person who sent 206out the patch. 207The strip count specifies how many slashes are to be stripped from 208the front of the pathname. 209(Any intervening directory names also go away.) 210For example, supposing the file name in the patch file was 211.Pa /u/howard/src/blurfl/blurfl.c : 212.Pp 213Setting 214.Fl p Ns Ar 0 215gives the entire pathname unmodified. 216.Pp 217.Fl p Ns Ar 1 218gives 219.Pp 220.D1 Pa u/howard/src/blurfl/blurfl.c 221.Pp 222without the leading slash. 223.Pp 224.Fl p Ns Ar 4 225gives 226.Pp 227.D1 Pa blurfl/blurfl.c 228.Pp 229Not specifying 230.Fl p 231at all just gives you 232.Pa blurfl.c , 233unless all of the directories in the leading path 234.Pq Pa u/howard/src/blurfl 235exist and that path is relative, 236in which case you get the entire pathname unmodified. 237Whatever you end up with is looked for either in the current directory, 238or the directory specified by the 239.Fl d 240option. 241.It Fl R , Fl Fl reverse 242Tells 243.Nm 244that this patch was created with the old and new files swapped. 245(Yes, I'm afraid that does happen occasionally, human nature being what it 246is.) 247.Nm 248will attempt to swap each hunk around before applying it. 249Rejects will come out in the swapped format. 250The 251.Fl R 252option will not work with ed diff scripts because there is too little 253information to reconstruct the reverse operation. 254.Pp 255If the first hunk of a patch fails, 256.Nm 257will reverse the hunk to see if it can be applied that way. 258If it can, you will be asked if you want to have the 259.Fl R 260option set. 261If it can't, the patch will continue to be applied normally. 262(Note: this method cannot detect a reversed patch if it is a normal diff 263and if the first command is an append (i.e. it should have been a delete) 264since appends always succeed, due to the fact that a null context will match 265anywhere. 266Luckily, most patches add or change lines rather than delete them, so most 267reversed normal diffs will begin with a delete, which will fail, triggering 268the heuristic.) 269.It Xo 270.Fl r Ar rej-name , 271.Fl Fl reject-file Ar rej-name 272.Xc 273Causes the next argument to be interpreted as the reject file name. 274.It Xo 275.Fl s , Fl Fl quiet , 276.Fl Fl silent 277.Xc 278Makes 279.Nm 280do its work silently, unless an error occurs. 281.It Fl t , Fl Fl batch 282Similar to 283.Fl f , 284in that it suppresses questions, but makes some different assumptions: 285skip patches for which a file to patch can't be found (the same as 286.Fl f ) ; 287skip patches for which the file has the wrong version for the 288.Qq Prereq: 289line in the patch; 290and assume that patches are reversed if they look like they are. 291.It Fl u , Fl Fl unified 292Forces 293.Nm 294to interpret the patch file as a unified context diff (a unidiff). 295.It Xo 296.Fl V Cm t | nil | never , 297.Fl Fl version-control Cm t | nil | never 298.Xc 299Causes the next argument to be interpreted as a method for creating 300backup file names. 301The type of backups made can also be given in the 302.Ev PATCH_VERSION_CONTROL 303or 304.Ev VERSION_CONTROL 305environment variables, which are overridden by this option. 306The 307.Fl B 308option overrides this option, causing the prefix to always be used for 309making backup file names. 310The values of the 311.Ev PATCH_VERSION_CONTROL 312and 313.Ev VERSION_CONTROL 314environment variables and the argument to the 315.Fl V 316option are like the GNU Emacs 317.Dq version-control 318variable; they also recognize synonyms that are more descriptive. 319The valid values are (unique abbreviations are accepted): 320.Bl -tag -width Ds -offset indent 321.It Cm t , numbered 322Always make numbered backups. 323.It Cm nil , existing 324Make numbered backups of files that already have them, 325simple backups of the others. 326.It Cm never , simple 327Always make simple backups. 328.El 329.It Fl v , Fl Fl version 330Causes 331.Nm 332to print out its revision header and patch level. 333.It Xo 334.Fl x Ar number , 335.Fl Fl debug Ar number 336.Xc 337Sets internal debugging flags, and is of interest only to 338.Nm 339patchers. 340.It Xo 341.Fl z Ar backup-ext , 342.Fl Fl suffix Ar backup-ext 343.Xc 344Causes the next argument to be interpreted as the backup extension, to be 345used in place of 346.Qq .orig . 347.It Fl Fl posix 348Enables strict 349.St -p1003.2 350conformance, specifically: 351.Bl -enum 352.It 353Backup files are not created unless the 354.Fl b 355option is specified. 356.It 357If unspecified, the file name used is the first of the old, new and 358index files that exists. 359.El 360.El 361.Ss Patch Application 362.Nm 363will try to skip any leading garbage, apply the diff, 364and then skip any trailing garbage. 365Thus you could feed an article or message containing a 366diff listing to 367.Nm patch , 368and it should work. 369If the entire diff is indented by a consistent amount, 370this will be taken into account. 371.Pp 372With context diffs, and to a lesser extent with normal diffs, 373.Nm 374can detect when the line numbers mentioned in the patch are incorrect, 375and will attempt to find the correct place to apply each hunk of the patch. 376As a first guess, it takes the line number mentioned for the hunk, plus or 377minus any offset used in applying the previous hunk. 378If that is not the correct place, 379.Nm 380will scan both forwards and backwards for a set of lines matching the context 381given in the hunk. 382First 383.Nm 384looks for a place where all lines of the context match. 385If no such place is found, and it's a context diff, and the maximum fuzz factor 386is set to 1 or more, then another scan takes place ignoring the first and last 387line of context. 388If that fails, and the maximum fuzz factor is set to 2 or more, 389the first two and last two lines of context are ignored, 390and another scan is made. 391.Pq The default maximum fuzz factor is 2. 392.Pp 393If 394.Nm 395cannot find a place to install that hunk of the patch, it will put the hunk 396out to a reject file, which normally is the name of the output file plus 397.Qq .rej . 398(Note that the rejected hunk will come out in context diff form whether the 399input patch was a context diff or a normal diff. 400If the input was a normal diff, many of the contexts will simply be null.) 401The line numbers on the hunks in the reject file may be different than 402in the patch file: they reflect the approximate location patch thinks the 403failed hunks belong in the new file rather than the old one. 404.Pp 405As each hunk is completed, you will be told whether the hunk succeeded or 406failed, and which line (in the new file) 407.Nm 408thought the hunk should go on. 409If this is different from the line number specified in the diff, 410you will be told the offset. 411A single large offset MAY be an indication that a hunk was installed in the 412wrong place. 413You will also be told if a fuzz factor was used to make the match, in which 414case you should also be slightly suspicious. 415.Ss Filename Determination 416If no original file is specified on the command line, 417.Nm 418will try to figure out from the leading garbage what the name of the file 419to edit is. 420When checking a prospective file name, pathname components are stripped 421as specified by the 422.Fl p 423option and the file's existence and writability are checked relative 424to the current working directory (or the directory specified by the 425.Fl d 426option). 427.Pp 428If the diff is a context or unified diff, 429.Nm 430is able to determine the old and new file names from the diff header. 431For context diffs, the 432.Dq old 433file is specified in the line beginning with 434.Qq *** 435and the 436.Dq new 437file is specified in the line beginning with 438.Qq --- . 439For a unified diff, the 440.Dq old 441file is specified in the line beginning with 442.Qq --- 443and the 444.Dq new 445file is specified in the line beginning with 446.Qq +++ . 447If there is an 448.Qq Index: 449line in the leading garbage (regardless of the diff type), 450.Nm 451will use the file name from that line as the 452.Dq index 453file. 454.Pp 455.Nm 456will choose the file name by performing the following steps, with the first 457match used: 458.Bl -enum 459.It 460If 461.Nm 462is operating in strict 463.St -p1003.2 464mode, the first of the 465.Dq old , 466.Dq new 467and 468.Dq index 469file names that exist is used. 470Otherwise, 471.Nm 472will examine either the 473.Dq old 474and 475.Dq new 476file names or, for a non-context diff, the 477.Dq index 478file name, and choose the file name with the fewest path components, 479the shortest basename, and the shortest total file name length (in that order). 480.It 481If no file exists, 482.Nm 483checks for the existence of the files in an SCCS or RCS directory 484(using the appropriate prefix or suffix) using the criteria specified 485above. 486If found, 487.Nm 488will attempt to get or check out the file. 489.It 490If no suitable file was found to patch, the patch file is a context or 491unified diff, and the old file was zero length, the new file name is 492created and used. 493.It 494If the file name still cannot be determined, 495.Nm 496will prompt the user for the file name to use. 497.El 498.Pp 499Additionally, if the leading garbage contains a 500.Qq Prereq:\ \& 501line, 502.Nm 503will take the first word from the prerequisites line (normally a version 504number) and check the input file to see if that word can be found. 505If not, 506.Nm 507will ask for confirmation before proceeding. 508.Pp 509The upshot of all this is that you should be able to say, while in a news 510interface, the following: 511.Pp 512.Dl | patch -d /usr/src/local/blurfl 513.Pp 514and patch a file in the blurfl directory directly from the article containing 515the patch. 516.Ss Backup Files 517By default, the patched version is put in place of the original, with 518the original file backed up to the same name with the extension 519.Qq .orig , 520or as specified by the 521.Fl B , 522.Fl V , 523or 524.Fl z 525options. 526The extension used for making backup files may also be specified in the 527.Ev SIMPLE_BACKUP_SUFFIX 528environment variable, which is overridden by the options above. 529.Pp 530If the backup file is a symbolic or hard link to the original file, 531.Nm 532creates a new backup file name by changing the first lowercase letter 533in the last component of the file's name into uppercase. 534If there are no more lowercase letters in the name, 535it removes the first character from the name. 536It repeats this process until it comes up with a 537backup file that does not already exist or is not linked to the original file. 538.Pp 539You may also specify where you want the output to go with the 540.Fl o 541option; if that file already exists, it is backed up first. 542.Ss Notes For Patch Senders 543There are several things you should bear in mind if you are going to 544be sending out patches: 545.Pp 546First, you can save people a lot of grief by keeping a 547.Pa patchlevel.h 548file which is patched to increment the patch level as the first diff in the 549patch file you send out. 550If you put a 551.Qq Prereq: 552line in with the patch, it won't let them apply 553patches out of order without some warning. 554.Pp 555Second, make sure you've specified the file names right, either in a 556context diff header, or with an 557.Qq Index: 558line. 559If you are patching something in a subdirectory, be sure to tell the patch 560user to specify a 561.Fl p 562option as needed. 563.Pp 564Third, you can create a file by sending out a diff that compares a 565null file to the file you want to create. 566This will only work if the file you want to create doesn't exist already in 567the target directory. 568.Pp 569Fourth, take care not to send out reversed patches, since it makes people wonder 570whether they already applied the patch. 571.Pp 572Fifth, while you may be able to get away with putting 582 diff listings into 573one file, it is probably wiser to group related patches into separate files in 574case something goes haywire. 575.Sh ENVIRONMENT 576.Bl -tag -width "PATCH_VERSION_CONTROL" -compact 577.It Ev POSIXLY_CORRECT 578When set, 579.Nm 580behaves as if the 581.Fl Fl posix 582option has been specified. 583.It Ev SIMPLE_BACKUP_SUFFIX 584Extension to use for backup file names instead of 585.Qq .orig . 586.It Ev TMPDIR 587Directory to put temporary files in; default is 588.Pa /tmp . 589.It Ev PATCH_VERSION_CONTROL 590Selects when numbered backup files are made. 591.It Ev VERSION_CONTROL 592Same as 593.Ev PATCH_VERSION_CONTROL . 594.El 595.Sh FILES 596.Bl -tag -width "$TMPDIR/patch*" -compact 597.It Pa $TMPDIR/patch* 598.Nm 599temporary files 600.It Pa /dev/tty 601used to read input when 602.Nm 603prompts the user 604.El 605.Sh DIAGNOSTICS 606Too many to list here, but generally indicative that 607.Nm 608couldn't parse your patch file. 609.Pp 610The message 611.Qq Hmm... 612indicates that there is unprocessed text in the patch file and that 613.Nm 614is attempting to intuit whether there is a patch in that text and, if so, 615what kind of patch it is. 616.Pp 617The 618.Nm 619utility exits with one of the following values: 620.Pp 621.Bl -tag -width Ds -compact -offset indent 622.It \&0 623Successful completion. 624.It \&1 625One or more lines were written to a reject file. 626.It \*[Gt]\&1 627An error occurred. 628.El 629.Pp 630When applying a set of patches in a loop it behooves you to check this 631exit status so you don't apply a later patch to a partially patched file. 632.Sh SEE ALSO 633.Xr diff 1 634.Sh AUTHORS 635.An Larry Wall 636with many other contributors. 637.Sh CAVEATS 638.Nm 639cannot tell if the line numbers are off in an ed script, and can only detect 640bad line numbers in a normal diff when it finds a 641.Qq change 642or a 643.Qq delete 644command. 645A context diff using fuzz factor 3 may have the same problem. 646Until a suitable interactive interface is added, you should probably do 647a context diff in these cases to see if the changes made sense. 648Of course, compiling without errors is a pretty good indication that the patch 649worked, but not always. 650.Pp 651.Nm 652usually produces the correct results, even when it has to do a lot of 653guessing. 654However, the results are guaranteed to be correct only when the patch is 655applied to exactly the same version of the file that the patch was 656generated from. 657.Sh BUGS 658Could be smarter about partial matches, excessively deviant offsets and 659swapped code, but that would take an extra pass. 660.Pp 661Check patch mode 662.Pq Fl C 663will fail if you try to check several patches in succession that build on 664each other. 665The entire 666.Nm 667code would have to be restructured to keep temporary files around so that it 668can handle this situation. 669.Pp 670If code has been duplicated (for instance with #ifdef OLDCODE ... #else ... 671#endif), 672.Nm 673is incapable of patching both versions, and, if it works at all, will likely 674patch the wrong one, and tell you that it succeeded to boot. 675.Pp 676If you apply a patch you've already applied, 677.Nm 678will think it is a reversed patch, and offer to un-apply the patch. 679This could be construed as a feature. 680