1.\" $OpenBSD: patch.1,v 1.17 2003/10/31 20:20:45 millert 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.Op Cm options 31.Op Ar origfile Op Ar patchfile 32.Nm patch 33.Pf \*(Lt Ar patchfile 34.Sh DESCRIPTION 35.Nm 36will take a patch file containing any of the four forms of difference 37listing produced by the 38.Xr diff 1 39program and apply those differences to an original file, 40producing a patched version. 41If 42.Ar patchfile 43is omitted, or is a hyphen, the patch will be read from the standard input. 44.Pp 45.Nm 46will attempt to determine the type of the diff listing, unless over-ruled by a 47.Fl c , 48.Fl e , 49.Fl n , 50or 51.Fl u 52option. 53Context diffs (old-style, new-style, and unified) and 54normal diffs are applied directly by the 55.Nm 56program itself, whereas ed diffs are simply fed to the 57.Xr ed 1 58editor via a pipe. 59.Pp 60If the 61.Ar patchfile 62contains more than one patch, 63.Nm 64will try to apply each of them as if they came from separate patch files. 65This means, among other things, that it is assumed that the name of the file 66to patch must be determined for each diff listing, and that the garbage before 67each diff listing will be examined for interesting things such as file names 68and revision level (see the section on 69.Sx Filename Determination 70below). 71.Pp 72The options are as follows: 73.Bl -tag -width Ds 74.It Fl b , Fl Fl backup 75Save a backup copy of the file before it is modified. 76By default the original file is saved with a backup extension of 77.Qq .orig 78unless the file already has a numbered backup, in which case a numbered 79backup is made. 80This is equivalent to specifying 81.Qo Fl V Ar existing Qc . 82This option is currently the default but that will change in a future release. 83.It Fl B , Fl Fl prefix 84Causes the next argument to be interpreted as a prefix to the backup file 85name. 86If this argument is specified, any argument to 87.Fl z 88will be ignored. 89.It Fl c , Fl Fl context 90Forces 91.Nm 92to interpret the patch file as a context diff. 93.It Fl C , Fl Fl check 94Checks that the patch would apply cleanly, but does not modify anything. 95.It Fl d , Fl Fl directory 96Causes 97.Nm 98to interpret the next argument as a directory, and 99.Xr cd 1 100to it before doing anything else. 101.It Fl D , Fl Fl ifdef 102Causes 103.Nm 104to use the 105.Qq #ifdef...#endif 106construct to mark changes. 107The argument following will be used as the differentiating symbol. 108Note that, unlike the C compiler, there must be a space between the 109.Fl D 110and the argument. 111.It Fl e , Fl Fl ed 112Forces 113.Nm 114to interpret the patch file as an 115.Xr ed 1 116script. 117.It Fl E , Fl Fl remove-empty-files 118Causes 119.Nm 120to remove output files that are empty after the patches have been applied. 121This option is useful when applying patches that create or remove files. 122.It Fl f , Fl Fl force 123Forces 124.Nm 125to assume that the user knows exactly what he or she is doing, and to not 126ask any questions. 127It assumes the following: 128skip patches for which a file to patch can't be found; 129patch files even though they have the wrong version for the 130.Qq Prereq: 131line in the patch; 132and assume that patches are not reversed even if they look like they are. 133This option does not suppress commentary; use 134.Fl s 135for that. 136.It Xo 137.Fl F Ns Aq Ar number , 138.Fl Fl fuzz Aq Ar number 139.Xc 140Sets the maximum fuzz factor. 141This option only applies to context diffs, and causes 142.Nm 143to ignore up to that many lines in looking for places to install a hunk. 144Note that a larger fuzz factor increases the odds of a faulty patch. 145The default fuzz factor is 2, and it may not be set to more than 146the number of lines of context in the context diff, ordinarily 3. 147.It Fl i , Fl Fl input 148Causes the next argument to be interpreted as the input file name 149(i.e. a patchfile). 150This option may be specified multiple times. 151.It Fl l , Fl Fl ignore-whitespace 152Causes the pattern matching to be done loosely, in case the tabs and 153spaces have been munged in your input file. 154Any sequence of whitespace in the pattern line will match any sequence 155in the input file. 156Normal characters must still match exactly. 157Each line of the context must still match a line in the input file. 158.It Fl n , Fl Fl normal 159Forces 160.Nm 161to interpret the patch file as a normal diff. 162.It Fl N , Fl Fl forward 163Causes 164.Nm 165to ignore patches that it thinks are reversed or already applied. 166See also 167.Fl R . 168.It Fl o , Fl Fl output 169Causes the next argument to be interpreted as the output file name. 170.It Xo 171.Fl p Ns Aq Ar number , 172.Fl Fl strip Aq Ar number 173.Xc 174Sets the pathname strip count, 175which controls how pathnames found in the patch file are treated, 176in case you keep your files in a different directory than the person who sent 177out the patch. 178The strip count specifies how many slashes are to be stripped from 179the front of the pathname. 180(Any intervening directory names also go away.) 181For example, supposing the file name in the patch file was 182.Pa /u/howard/src/blurfl/blurfl.c : 183.Pp 184Setting 185.Fl p Ns Ar 0 186gives the entire pathname unmodified. 187.Pp 188.Fl p Ns Ar 1 189gives 190.Pp 191.D1 Pa u/howard/src/blurfl/blurfl.c 192.Pp 193without the leading slash. 194.Pp 195.Fl p Ns Ar 4 196gives 197.Pp 198.D1 Pa blurfl/blurfl.c 199.Pp 200Not specifying 201.Fl p 202at all just gives you 203.Pa blurfl.c , 204unless all of the directories in the leading path 205.Pq Pa u/howard/src/blurfl 206exist and that path is relative, 207in which case you get the entire pathname unmodified. 208Whatever you end up with is looked for either in the current directory, 209or the directory specified by the 210.Fl d 211option. 212.It Fl r , Fl Fl reject-file 213Causes the next argument to be interpreted as the reject file name. 214.It Fl R , Fl Fl reverse 215Tells 216.Nm 217that this patch was created with the old and new files swapped. 218(Yes, I'm afraid that does happen occasionally, human nature being what it 219is.) 220.Nm 221will attempt to swap each hunk around before applying it. 222Rejects will come out in the swapped format. 223The 224.Fl R 225option will not work with ed diff scripts because there is too little 226information to reconstruct the reverse operation. 227.Pp 228If the first hunk of a patch fails, 229.Nm 230will reverse the hunk to see if it can be applied that way. 231If it can, you will be asked if you want to have the 232.Fl R 233option set. 234If it can't, the patch will continue to be applied normally. 235(Note: this method cannot detect a reversed patch if it is a normal diff 236and if the first command is an append (i.e. it should have been a delete) 237since appends always succeed, due to the fact that a null context will match 238anywhere. 239Luckily, most patches add or change lines rather than delete them, so most 240reversed normal diffs will begin with a delete, which will fail, triggering 241the heuristic.) 242.It Xo 243.Fl s , Fl Fl quiet , 244.Fl Fl silent 245.Xc 246Makes 247.Nm 248do its work silently, unless an error occurs. 249.It Fl t , Fl Fl batch 250Similar to 251.Fl f , 252in that it suppresses questions, but makes some different assumptions: 253skip patches for which a file to patch can't be found (the same as 254.Fl f ) ; 255skip patches for which the file has the wrong version for the 256.Qq Prereq: 257line in the patch; 258and assume that patches are reversed if they look like they are. 259.It Fl u , Fl Fl unified 260Forces 261.Nm 262to interpret the patch file as a unified context diff (a unidiff). 263.It Fl v , Fl Fl version 264Causes 265.Nm 266to print out its revision header and patch level. 267.It Fl V , Fl Fl version-control 268Causes the next argument to be interpreted as a method for creating 269backup file names. 270The type of backups made can also be given in the 271.Ev PATCH_VERSION_CONTROL 272or 273.Ev VERSION_CONTROL 274environment variables, which are overridden by this option. 275The 276.Fl B 277option overrides this option, causing the prefix to always be used for 278making backup file names. 279The values of the 280.Ev PATCH_VERSION_CONTROL 281and 282.Ev VERSION_CONTROL 283environment variables and the argument to the 284.Fl V 285option are like the GNU Emacs 286.Dq version-control 287variable; they also recognize synonyms that are more descriptive. 288The valid values are (unique abbreviations are accepted): 289.Bl -tag -width Ds -offset indent 290.It t , numbered 291Always make numbered backups. 292.It nil , existing 293Make numbered backups of files that already have them, 294simple backups of the others. 295.It never , simple 296Always make simple backups. 297.El 298.It Xo 299.Fl x Ns Aq Ar number , 300.Fl Fl debug Aq Ar number 301.Xc 302Sets internal debugging flags, and is of interest only to 303.Nm 304patchers. 305.It Fl z , Fl Fl suffix 306Causes the next argument to be interpreted as the backup extension, to be 307used in place of 308.Qq .orig . 309.It Fl Fl posix 310Enables strict 311.St -p1003.2 312conformance, specifically: 313.Bl -enum 314.It 315Backup files are not created unless the 316.Fl b 317option is specified. 318.It 319If unspecified, the file name used is the first of the old, new and 320index files that exists. 321.El 322.El 323.Ss Patch Application 324.Nm 325will try to skip any leading garbage, apply the diff, 326and then skip any trailing garbage. 327Thus you could feed an article or message containing a 328diff listing to 329.Nm patch , 330and it should work. 331If the entire diff is indented by a consistent amount, 332this will be taken into account. 333.Pp 334With context diffs, and to a lesser extent with normal diffs, 335.Nm 336can detect when the line numbers mentioned in the patch are incorrect, 337and will attempt to find the correct place to apply each hunk of the patch. 338As a first guess, it takes the line number mentioned for the hunk, plus or 339minus any offset used in applying the previous hunk. 340If that is not the correct place, 341.Nm 342will scan both forwards and backwards for a set of lines matching the context 343given in the hunk. 344First 345.Nm 346looks for a place where all lines of the context match. 347If no such place is found, and it's a context diff, and the maximum fuzz factor 348is set to 1 or more, then another scan takes place ignoring the first and last 349line of context. 350If that fails, and the maximum fuzz factor is set to 2 or more, 351the first two and last two lines of context are ignored, 352and another scan is made. 353.Pq The default maximum fuzz factor is 2. 354.Pp 355If 356.Nm 357cannot find a place to install that hunk of the patch, it will put the hunk 358out to a reject file, which normally is the name of the output file plus 359.Qq .rej . 360(Note that the rejected hunk will come out in context diff form whether the 361input patch was a context diff or a normal diff. 362If the input was a normal diff, many of the contexts will simply be null.) 363The line numbers on the hunks in the reject file may be different than 364in the patch file: they reflect the approximate location patch thinks the 365failed hunks belong in the new file rather than the old one. 366.Pp 367As each hunk is completed, you will be told whether the hunk succeeded or 368failed, and which line (in the new file) 369.Nm 370thought the hunk should go on. 371If this is different from the line number specified in the diff, 372you will be told the offset. 373A single large offset MAY be an indication that a hunk was installed in the 374wrong place. 375You will also be told if a fuzz factor was used to make the match, in which 376case you should also be slightly suspicious. 377.Ss Filename Determination 378If no original file is specified on the command line, 379.Nm 380will try to figure out from the leading garbage what the name of the file 381to edit is. 382When checking a prospective file name, pathname components are stripped 383as specified by the 384.Fl p 385option and the file's existence and writability are checked relative 386to the current working directory (or the directory specified by the 387.Fl d 388option). 389.Pp 390If the diff is a context or unified diff, 391.Nm 392is able to determine the old and new file names from the diff header. 393For context diffs, the 394.Dq old 395file is specified in the line beginning with 396.Qq *** 397and the 398.Dq new 399file is specified in the line beginning with 400.Qq --- . 401For a unified diff, the 402.Dq old 403file is specified in the line beginning with 404.Qq --- 405and the 406.Dq new 407file is specified in the line beginning with 408.Qq +++ . 409If there is an 410.Qq Index: 411line in the leading garbage (regardless of the diff type), 412.Nm 413will use the file name from that line as the 414.Dq index 415file. 416.Pp 417.Nm 418will choose the file name by performing the following steps, with the first 419match used: 420.Bl -enum 421.It 422If 423.Nm 424is operating in strict 425.St -p1003.2 426mode, the first of the 427.Dq old , 428.Dq new 429and 430.Dq index 431file names that exist is used. 432Otherwise, 433.Nm 434will examine either the 435.Dq old 436and 437.Dq new 438file names or, for a non-context diff, the 439.Dq index 440file name, and choose the file name with the fewest path components, 441the shortest basename, and the shortest total file name length (in that order). 442.It 443If no file exists, 444.Nm 445checks for the existence of the files in an SCCS or RCS directory 446(using the appropriate prefix or suffix) using the criteria specified 447above. 448If found, 449.Nm 450will attempt to get or check out the file. 451.It 452If no suitable file was found to patch, the patch file is a context or 453unified diff, and the old file was zero length, the new file name is 454created and used. 455.It 456If the file name still cannot be determined, 457.Nm 458will prompt the user for the file name to use. 459.El 460.Pp 461Additionally, if the leading garbage contains a 462.Qq Prereq:\ \& 463line, 464.Nm 465will take the first word from the prerequisites line (normally a version 466number) and check the input file to see if that word can be found. 467If not, 468.Nm 469will ask for confirmation before proceeding. 470.Pp 471The upshot of all this is that you should be able to say, while in a news 472interface, the following: 473.Pp 474.Dl | patch -d /usr/src/local/blurfl 475.Pp 476and patch a file in the blurfl directory directly from the article containing 477the patch. 478.Ss Backup Files 479By default, the patched version is put in place of the original, with 480the original file backed up to the same name with the extension 481.Qq .orig , 482or as specified by the 483.Fl B , 484.Fl V , 485or 486.Fl z 487options. 488The extension used for making backup files may also be specified in the 489.Ev SIMPLE_BACKUP_SUFFIX 490environment variable, which is overridden by the options above. 491.Pp 492If the backup file is a symbolic or hard link to the original file, 493.Nm 494creates a new backup file name by changing the first lowercase letter 495in the last component of the file's name into uppercase. 496If there are no more lowercase letters in the name, 497it removes the first character from the name. 498It repeats this process until it comes up with a 499backup file that does not already exist or is not linked to the original file. 500.Pp 501You may also specify where you want the output to go with the 502.Fl o 503option; if that file already exists, it is backed up first. 504.Ss Notes For Patch Senders 505There are several things you should bear in mind if you are going to 506be sending out patches: 507.Pp 508First, you can save people a lot of grief by keeping a 509.Pa patchlevel.h 510file which is patched to increment the patch level as the first diff in the 511patch file you send out. 512If you put a 513.Qq Prereq: 514line in with the patch, it won't let them apply 515patches out of order without some warning. 516.Pp 517Second, make sure you've specified the file names right, either in a 518context diff header, or with an 519.Qq Index: 520line. 521If you are patching something in a subdirectory, be sure to tell the patch 522user to specify a 523.Fl p 524option as needed. 525.Pp 526Third, you can create a file by sending out a diff that compares a 527null file to the file you want to create. 528This will only work if the file you want to create doesn't exist already in 529the target directory. 530.Pp 531Fourth, take care not to send out reversed patches, since it makes people wonder 532whether they already applied the patch. 533.Pp 534Fifth, while you may be able to get away with putting 582 diff listings into 535one file, it is probably wiser to group related patches into separate files in 536case something goes haywire. 537.Sh ENVIRONMENT 538.Bl -tag -width "PATCH_VERSION_CONTROL" -compact 539.It Ev POSIXLY_CORRECT 540When set, 541.Nm 542behaves as if the 543.Fl Fl posix 544option has been specified. 545.It Ev SIMPLE_BACKUP_SUFFIX 546Extension to use for backup file names instead of 547.Qq .orig . 548.It Ev TMPDIR 549Directory to put temporary files in; default is 550.Pa /tmp . 551.It Ev PATCH_VERSION_CONTROL 552Selects when numbered backup files are made. 553.It Ev VERSION_CONTROL 554Same as 555.Ev PATCH_VERSION_CONTROL . 556.El 557.Sh FILES 558.Bl -tag -width "$TMPDIR/patch*" -compact 559.It Pa $TMPDIR/patch* 560.Nm 561temporary files 562.It Pa /dev/tty 563used to read input when 564.Nm 565prompts the user 566.El 567.Sh DIAGNOSTICS 568Too many to list here, but generally indicative that 569.Nm 570couldn't parse your patch file. 571.Pp 572The message 573.Qq Hmm... 574indicates that there is unprocessed text in the patch file and that 575.Nm 576is attempting to intuit whether there is a patch in that text and, if so, 577what kind of patch it is. 578.Pp 579The 580.Nm 581utility exits with one of the following values: 582.Pp 583.Bl -tag -width Ds -compact -offset indent 584.It \&0 585Successful completion. 586.It \&1 587One or more lines were written to a reject file. 588.It \*[Gt]\&1 589An error occurred. 590.El 591.Pp 592When applying a set of patches in a loop it behooves you to check this 593exit status so you don't apply a later patch to a partially patched file. 594.Sh SEE ALSO 595.Xr diff 1 596.Sh AUTHORS 597.An Larry Wall 598with many other contributors. 599.Sh CAVEATS 600.Nm 601cannot tell if the line numbers are off in an ed script, and can only detect 602bad line numbers in a normal diff when it finds a 603.Qq change 604or a 605.Qq delete 606command. 607A context diff using fuzz factor 3 may have the same problem. 608Until a suitable interactive interface is added, you should probably do 609a context diff in these cases to see if the changes made sense. 610Of course, compiling without errors is a pretty good indication that the patch 611worked, but not always. 612.Pp 613.Nm 614usually produces the correct results, even when it has to do a lot of 615guessing. 616However, the results are guaranteed to be correct only when the patch is 617applied to exactly the same version of the file that the patch was 618generated from. 619.Sh BUGS 620Could be smarter about partial matches, excessively deviant offsets and 621swapped code, but that would take an extra pass. 622.Pp 623Check patch mode 624.Pq Fl C 625will fail if you try to check several patches in succession that build on 626each other. 627The entire 628.Nm 629code would have to be restructured to keep temporary files around so that it 630can handle this situation. 631.Pp 632If code has been duplicated (for instance with #ifdef OLDCODE ... #else ... 633#endif), 634.Nm 635is incapable of patching both versions, and, if it works at all, will likely 636patch the wrong one, and tell you that it succeeded to boot. 637.Pp 638If you apply a patch you've already applied, 639.Nm 640will think it is a reversed patch, and offer to un-apply the patch. 641This could be construed as a feature. 642