1.\" $OpenBSD: patch.1,v 1.33 2021/11/09 16:13:40 jmc 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 $Mdocdate: November 9 2021 $ 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 overruled by a 61.Fl c , 62.Fl e , 63.Fl n , 64or 65.Fl u 66option. 67.Pp 68If the 69.Ar patchfile 70contains more than one patch, 71.Nm 72will try to apply each of them as if they came from separate patch files. 73This means, among other things, that it is assumed that the name of the file 74to patch must be determined for each diff listing, and that the garbage before 75each diff listing will be examined for interesting things such as file names 76and revision level (see the section on 77.Sx Filename Determination 78below). 79.Pp 80The options are as follows: 81.Bl -tag -width Ds 82.It Xo 83.Fl B Ar backup-prefix , 84.Fl Fl prefix Ar backup-prefix 85.Xc 86Causes the next argument to be interpreted as a prefix to the backup file 87name. 88If this argument is specified, any argument to 89.Fl z 90will be ignored. 91.It Fl b , Fl Fl backup 92Save a backup copy of the file before it is modified. 93By default the original file is saved with a backup extension of 94.Qq .orig 95unless the file already has a numbered backup, in which case a numbered 96backup is made. 97This is equivalent to specifying 98.Qo Fl V Cm existing Qc . 99This option is currently the default, unless 100.Fl -posix 101is specified. 102.It Fl C , Fl Fl check , Fl Fl dry-run 103Checks that the patch would apply cleanly, but does not modify anything. 104.It Fl c , Fl Fl context 105Forces 106.Nm 107to interpret the patch file as a context diff. 108.It Xo 109.Fl D Ar symbol , 110.Fl Fl ifdef Ar symbol 111.Xc 112Causes 113.Nm 114to use the 115.Qq #ifdef...#endif 116construct to mark changes. 117The argument following will be used as the differentiating symbol. 118Note that, unlike the C compiler, there must be a space between the 119.Fl D 120and the argument. 121.It Xo 122.Fl d Ar directory , 123.Fl Fl directory Ar directory 124.Xc 125Causes 126.Nm 127to interpret the next argument as a directory, 128and change working directory to it before doing anything else. 129.It Fl E , Fl Fl remove-empty-files 130Causes 131.Nm 132to remove output files that are empty after the patches have been applied. 133This option is useful when applying patches that create or remove files. 134.It Fl e , Fl Fl ed 135Forces 136.Nm 137to interpret the patch file as an 138.Xr ed 1 139script. 140.It Xo 141.Fl F Ar max-fuzz , 142.Fl Fl fuzz Ar max-fuzz 143.Xc 144Sets the maximum fuzz factor. 145This option only applies to context diffs, and causes 146.Nm 147to ignore up to that many lines in looking for places to install a hunk. 148Note that a larger fuzz factor increases the odds of a faulty patch. 149The default fuzz factor is 2, and it may not be set to more than 150the number of lines of context in the context diff, ordinarily 3. 151.It Fl f , Fl Fl force 152Forces 153.Nm 154to assume that the user knows exactly what he or she is doing, and to not 155ask any questions. 156It assumes the following: 157skip patches for which a file to patch can't be found; 158patch files even though they have the wrong version for the 159.Qq Prereq: 160line in the patch; 161and assume that patches are not reversed even if they look like they are. 162This option does not suppress commentary; use 163.Fl s 164for that. 165.It Xo 166.Fl i Ar patchfile , 167.Fl Fl input Ar patchfile 168.Xc 169Causes the next argument to be interpreted as the input file name 170(i.e. a patchfile). 171.It Fl l , Fl Fl ignore-whitespace 172Causes the pattern matching to be done loosely, in case the tabs and 173spaces have been munged in your input file. 174Any sequence of whitespace in the pattern line will match any sequence 175in the input file. 176Normal characters must still match exactly. 177Each line of the context must still match a line in the input file. 178.It Fl N , Fl Fl forward 179Causes 180.Nm 181to ignore patches that it thinks are reversed or already applied. 182See also 183.Fl R . 184.It Fl n , Fl Fl normal 185Forces 186.Nm 187to interpret the patch file as a normal diff. 188.It Xo 189.Fl o Ar out-file , 190.Fl Fl output Ar out-file 191.Xc 192Causes the next argument to be interpreted as the output file name. 193.It Xo 194.Fl p Ar strip-count , 195.Fl Fl strip Ar strip-count 196.Xc 197Sets the pathname strip count, 198which controls how pathnames found in the patch file are treated, 199in case you keep your files in a different directory than the person who sent 200out the patch. 201The strip count specifies how many slashes are to be stripped from 202the front of the pathname. 203(Any intervening directory names also go away.) 204For example, supposing the file name in the patch file was 205.Pa /u/howard/src/blurfl/blurfl.c : 206.Pp 207Setting 208.Fl p Ns Ar 0 209gives the entire pathname unmodified. 210.Pp 211.Fl p Ns Ar 1 212gives 213.Pp 214.D1 Pa u/howard/src/blurfl/blurfl.c 215.Pp 216without the leading slash. 217.Pp 218.Fl p Ns Ar 4 219gives 220.Pp 221.D1 Pa blurfl/blurfl.c 222.Pp 223Not specifying 224.Fl p 225at all just gives you 226.Pa blurfl.c , 227unless all of the directories in the leading path 228.Pq Pa u/howard/src/blurfl 229exist and that path is relative, 230in which case you get the entire pathname unmodified. 231Whatever you end up with is looked for either in the current directory, 232or the directory specified by the 233.Fl d 234option. 235.It Fl R , Fl Fl reverse 236Tells 237.Nm 238that this patch was created with the old and new files swapped. 239(Yes, I'm afraid that does happen occasionally, human nature being what it 240is.) 241.Nm 242will attempt to swap each hunk around before applying it. 243Rejects will come out in the swapped format. 244The 245.Fl R 246option will not work with ed diff scripts because there is too little 247information to reconstruct the reverse operation. 248.Pp 249If the first hunk of a patch fails, 250.Nm 251will reverse the hunk to see if it can be applied that way. 252If it can, you will be asked if you want to have the 253.Fl R 254option set. 255If it can't, the patch will continue to be applied normally. 256(Note: this method cannot detect a reversed patch if it is a normal diff 257and if the first command is an append (i.e. it should have been a delete) 258since appends always succeed, due to the fact that a null context will match 259anywhere. 260Luckily, most patches add or change lines rather than delete them, so most 261reversed normal diffs will begin with a delete, which will fail, triggering 262the heuristic.) 263.It Xo 264.Fl r Ar rej-name , 265.Fl Fl reject-file Ar rej-name 266.Xc 267Causes the next argument to be interpreted as the reject file name. 268.It Xo 269.Fl s , Fl Fl quiet , 270.Fl Fl silent 271.Xc 272Makes 273.Nm 274do its work silently, unless an error occurs. 275.It Fl t , Fl Fl batch 276Similar to 277.Fl f , 278in that it suppresses questions, but makes some different assumptions: 279skip patches for which a file to patch can't be found (the same as 280.Fl f ) ; 281skip patches for which the file has the wrong version for the 282.Qq Prereq: 283line in the patch; 284and assume that patches are reversed if they look like they are. 285.It Fl u , Fl Fl unified 286Forces 287.Nm 288to interpret the patch file as a unified context diff (a unidiff). 289.It Xo 290.Fl V Cm t | nil | never , 291.Fl Fl version-control Cm t | nil | never 292.Xc 293Causes the next argument to be interpreted as a method for creating 294backup file names. 295The type of backups made can also be given in the 296.Ev PATCH_VERSION_CONTROL 297or 298.Ev VERSION_CONTROL 299environment variables, which are overridden by this option. 300The 301.Fl B 302option overrides this option, causing the prefix to always be used for 303making backup file names. 304The values of the 305.Ev PATCH_VERSION_CONTROL 306and 307.Ev VERSION_CONTROL 308environment variables and the argument to the 309.Fl V 310option are like the GNU Emacs 311.Dq version-control 312variable; they also recognize synonyms that are more descriptive. 313The valid values are (unique abbreviations are accepted): 314.Bl -tag -width Ds -offset indent 315.It Cm t , numbered 316Always make numbered backups. 317.It Cm nil , existing 318Make numbered backups of files that already have them, 319simple backups of the others. 320.It Cm never , simple 321Always make simple backups. 322.El 323.It Fl v , Fl Fl version 324Causes 325.Nm 326to print out its revision header and patch level. 327.It Xo 328.Fl x Ar number , 329.Fl Fl debug Ar number 330.Xc 331Sets internal debugging flags, and is of interest only to 332.Nm 333patchers. 334.It Xo 335.Fl z Ar backup-ext , 336.Fl Fl suffix Ar backup-ext 337.Xc 338Causes the next argument to be interpreted as the backup extension, to be 339used in place of 340.Qq .orig . 341.It Fl Fl posix 342Enables strict 343.St -p1003.1-2008 344conformance, specifically: 345.Bl -enum 346.It 347Backup files are not created unless the 348.Fl b 349option is specified. 350.It 351If unspecified, the file name used is the first of the old, new and 352index files that exists. 353.El 354.El 355.Ss Patch Application 356.Nm 357will try to skip any leading garbage, apply the diff, 358and then skip any trailing garbage. 359Thus you could feed an article or message containing a 360diff listing to 361.Nm patch , 362and it should work. 363If the entire diff is indented by a consistent amount, 364this will be taken into account. 365.Pp 366With context diffs, and to a lesser extent with normal diffs, 367.Nm 368can detect when the line numbers mentioned in the patch are incorrect, 369and will attempt to find the correct place to apply each hunk of the patch. 370As a first guess, it takes the line number mentioned for the hunk, plus or 371minus any offset used in applying the previous hunk. 372If that is not the correct place, 373.Nm 374will scan both forwards and backwards for a set of lines matching the context 375given in the hunk. 376First 377.Nm 378looks for a place where all lines of the context match. 379If no such place is found, and it's a context diff, and the maximum fuzz factor 380is set to 1 or more, then another scan takes place ignoring the first and last 381line of context. 382If that fails, and the maximum fuzz factor is set to 2 or more, 383the first two and last two lines of context are ignored, 384and another scan is made. 385.Pq The default maximum fuzz factor is 2. 386.Pp 387If 388.Nm 389cannot find a place to install that hunk of the patch, it will put the hunk 390out to a reject file, which normally is the name of the output file plus 391.Qq .rej . 392(Note that the rejected hunk will come out in context diff form whether the 393input patch was a context diff or a normal diff. 394If the input was a normal diff, many of the contexts will simply be null.) 395The line numbers on the hunks in the reject file may be different than 396in the patch file: they reflect the approximate location patch thinks the 397failed hunks belong in the new file rather than the old one. 398.Pp 399As each hunk is completed, you will be told whether the hunk succeeded or 400failed, and which line (in the new file) 401.Nm 402thought the hunk should go on. 403If this is different from the line number specified in the diff, 404you will be told the offset. 405A single large offset MAY be an indication that a hunk was installed in the 406wrong place. 407You will also be told if a fuzz factor was used to make the match, in which 408case you should also be slightly suspicious. 409.Ss Filename Determination 410If no original file is specified on the command line, 411.Nm 412will try to figure out from the leading garbage what the name of the file 413to edit is. 414When checking a prospective file name, pathname components are stripped 415as specified by the 416.Fl p 417option and the file's existence and writability are checked relative 418to the current working directory (or the directory specified by the 419.Fl d 420option). 421.Pp 422If the diff is a context or unified diff, 423.Nm 424is able to determine the old and new file names from the diff header. 425For context diffs, the 426.Dq old 427file is specified in the line beginning with 428.Qq *** 429and the 430.Dq new 431file is specified in the line beginning with 432.Qq --- . 433For a unified diff, the 434.Dq old 435file is specified in the line beginning with 436.Qq --- 437and the 438.Dq new 439file is specified in the line beginning with 440.Qq +++ . 441If there is an 442.Qq Index: 443line in the leading garbage (regardless of the diff type), 444.Nm 445will use the file name from that line as the 446.Dq index 447file. 448.Pp 449.Nm 450will choose the file name by performing the following steps, with the first 451match used: 452.Bl -enum 453.It 454If 455.Nm 456is operating in strict 457.St -p1003.1-2008 458mode, the first of the 459.Dq old , 460.Dq new 461and 462.Dq index 463file names that exist is used. 464Otherwise, 465.Nm 466will examine either the 467.Dq old 468and 469.Dq new 470file names or, for a non-context diff, the 471.Dq index 472file name, and choose the file name with the fewest path components, 473the shortest basename, and the shortest total file name length (in that order). 474.It 475If no suitable file was found to patch, the patch file is a context or 476unified diff, and the old file was zero length, the new file name is 477created and used. 478.It 479If the file name still cannot be determined, 480.Nm 481will prompt the user for the file name to use. 482.El 483.Pp 484Additionally, if the leading garbage contains a 485.Qq Prereq:\ \& 486line, 487.Nm 488will take the first word from the prerequisites line (normally a version 489number) and check the input file to see if that word can be found. 490If not, 491.Nm 492will ask for confirmation before proceeding. 493.Pp 494The upshot of all this is that you should be able to say, while in a news 495interface, the following: 496.Pp 497.Dl | patch -d /usr/src/local/blurfl 498.Pp 499and patch a file in the blurfl directory directly from the article containing 500the patch. 501.Ss Backup Files 502By default, the patched version is put in place of the original, with 503the original file backed up to the same name with the extension 504.Qq .orig , 505or as specified by the 506.Fl B , 507.Fl V , 508or 509.Fl z 510options. 511The extension used for making backup files may also be specified in the 512.Ev SIMPLE_BACKUP_SUFFIX 513environment variable, which is overridden by the options above. 514.Pp 515If the backup file is a symbolic or hard link to the original file, 516.Nm 517creates a new backup file name by changing the first lowercase letter 518in the last component of the file's name into uppercase. 519If there are no more lowercase letters in the name, 520it removes the first character from the name. 521It repeats this process until it comes up with a 522backup file that does not already exist or is not linked to the original file. 523.Pp 524You may also specify where you want the output to go with the 525.Fl o 526option; if that file already exists, it is backed up first. 527.Ss Notes For Patch Senders 528There are several things you should bear in mind if you are going to 529be sending out patches: 530.Pp 531First, you can save people a lot of grief by keeping a 532.Pa patchlevel.h 533file which is patched to increment the patch level as the first diff in the 534patch file you send out. 535If you put a 536.Qq Prereq: 537line in with the patch, it won't let them apply 538patches out of order without some warning. 539.Pp 540Second, make sure you've specified the file names right, either in a 541context diff header, or with an 542.Qq Index: 543line. 544If you are patching something in a subdirectory, be sure to tell the patch 545user to specify a 546.Fl p 547option as needed. 548.Pp 549Third, you can create a file by sending out a diff that compares a 550null file to the file you want to create. 551This will only work if the file you want to create doesn't exist already in 552the target directory. 553.Pp 554Fourth, take care not to send out reversed patches, since it makes people wonder 555whether they already applied the patch. 556.Pp 557Fifth, while you may be able to get away with putting 582 diff listings into 558one file, it is probably wiser to group related patches into separate files in 559case something goes haywire. 560.Sh ENVIRONMENT 561.Bl -tag -width "PATCH_VERSION_CONTROL" -compact 562.It Ev POSIXLY_CORRECT 563When set, 564.Nm 565behaves as if the 566.Fl Fl posix 567option has been specified. 568.It Ev SIMPLE_BACKUP_SUFFIX 569Extension to use for backup file names instead of 570.Qq .orig . 571.It Ev TMPDIR 572Directory to put temporary files in; default is 573.Pa /tmp . 574.It Ev PATCH_VERSION_CONTROL 575Selects when numbered backup files are made. 576.It Ev VERSION_CONTROL 577Same as 578.Ev PATCH_VERSION_CONTROL . 579.El 580.Sh FILES 581.Bl -tag -width "$TMPDIR/patch*" -compact 582.It Pa $TMPDIR/patch* 583.Nm 584temporary files 585.It Pa /dev/tty 586used to read input when 587.Nm 588prompts the user 589.El 590.Sh EXIT STATUS 591The 592.Nm 593utility exits with one of the following values: 594.Pp 595.Bl -tag -width Ds -offset indent -compact 596.It 0 597Successful completion. 598.It 1 599One or more lines were written to a reject file. 600.It \*(Gt1 601An error occurred. 602.El 603.Pp 604When applying a set of patches in a loop it behooves you to check this 605exit status so you don't apply a later patch to a partially patched file. 606.Sh DIAGNOSTICS 607Too many to list here, but generally indicative that 608.Nm 609couldn't parse your patch file. 610.Pp 611The message 612.Qq Hmm... 613indicates that there is unprocessed text in the patch file and that 614.Nm 615is attempting to intuit whether there is a patch in that text and, if so, 616what kind of patch it is. 617.Sh SEE ALSO 618.Xr diff 1 619.Sh STANDARDS 620The 621.Nm 622utility is compliant with the 623.St -p1003.1-2008 624specification, 625except as detailed above for the 626.Fl -posix 627option. 628.Pp 629The flags 630.Op Fl BCEFfstVvxz 631and 632.Op Fl -posix 633are extensions to that specification. 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