''' $Header: patch.man,v 2.0 86/09/17 15:39:09 lwall Exp $''' ''' $Log:	patch.man,v $''' Revision 2.0  86/09/17  15:39:09  lwall''' Baseline for netwide release.''' ''' Revision 1.4  86/08/01  19:23:22  lwall''' Documented -v, -p, -F.''' Added notes to patch senders.''' ''' Revision 1.3  85/03/26  15:11:06  lwall''' Frozen.''' ''' Revision 1.2.1.4  85/03/12  16:14:27  lwall''' Documented -p.''' ''' Revision 1.2.1.3  85/03/12  16:09:41  lwall''' Documented -D.''' ''' Revision 1.2.1.2  84/12/05  11:06:55  lwall''' Added -l switch, and noted bistability bug.''' ''' Revision 1.2.1.1  84/12/04  17:23:39  lwall''' Branch for sdcrdcf changes.''' ''' Revision 1.2  84/12/04  17:22:02  lwall''' Baseline version.''' .de Sh.br.ne 5.PP\fB\\$1\fR.PP...de Sp.if t .sp .5v.if n .sp..''''''     Set up \*(-- to give an unbreakable dash;'''     string Tr holds user defined translation string.'''     Bell System Logo is used as a dummy character.'''.ie n \{\.tr \(bs-\*(Tr.ds -- \(bs-.if (\n(.H=4u)&(1m=24u) .ds -- \(bs\h'-12u'\(bs\h'-12u'-\" diablo 10 pitch.if (\n(.H=4u)&(1m=20u) .ds -- \(bs\h'-12u'\(bs\h'-8u'-\" diablo 12 pitch.ds L" "".ds R" "".ds L' '.ds R' ''br\}.el\{\.ds -- \(em\|.tr \*(Tr.ds L" ``.ds R" ''.ds L' `.ds R' ''br\}.TH PATCH 1 "June 30, 1993".SH NAMEpatch \- a program for applying a diff file to an original.SH SYNOPSIS.B patch[options] orig patchfile [+ [options] orig].spbut usually just.sp.B patch<patchfile.SH DESCRIPTION.I Patchwill take a patch file containing any of the three forms of differencelisting produced by the.I diffprogram and apply those differences to an original file, producing a patchedversion.By default, the patched version is put in place of the original, withthe original file backed up to the same name with theextension \*(L".orig\*(R", or as specified by the.B -bswitch.You may also specify where you want the output to go with a.B -oswitch.If.I patchfileis omitted, or is a hyphen, the patch will be read from standard input..PPUpon startup, patch will attempt to determine the type of the diff listing,unless over-ruled by a.BR -c ,.BR -e ,or.B -nswitch.Context diffs and normal diffs are applied by the.I patchprogram itself, while ed diffs are simply fed to the.I ededitor via a pipe..PP.I Patchwill try to skip any leading garbage, apply the diff,and then skip any trailing garbage.Thus you could feed an article or message containing adiff listing to.IR patch ,and it should work.If the entire diff is indented by a consistent amount,this will be taken into account..PPWith context diffs, and to a lesser extent with normal diffs,.I patchcan detect when the line numbers mentioned in the patch are incorrect,and will attempt to find the correct place to apply each hunk of the patch.As a first guess, it takes the line number mentioned for the hunk, plus orminus any offset used in applying the previous hunk.If that is not the correct place,.I patchwill scan both forwards and backwards for a set of lines matching the contextgiven in the hunk.First.I patchlooks for a place where all lines of the context match.If no such place is found, and it's a context diff, and the maximum fuzz factoris set to 1 or more, then another scan takes place ignoring the first and lastline of context.If that fails, and the maximum fuzz factor is set to 2 or more,the first two and last two lines of context are ignored,and another scan is made.(The default maximum fuzz factor is 2.)If.I patchcannot find a place to install that hunk of the patch, it will put thehunk out to a reject file, which normally is the name of the output fileplus \*(L".rej\*(R".(Note that the rejected hunk will come out in context diff form whether theinput patch was a context diff or a normal diff.If the input was a normal diff, many of the contexts will simply be null.)The line numbers on the hunks in the reject file may be different thanin the patch file: they reflect the approximate location patch thinks thefailed hunks belong in the new file rather than the old one..PPAs each hunk is completed, you will be told whether the hunk succeeded orfailed, and which line (in the new file).I patchthought the hunk should go on.If this is different from the line number specified in the diff you willbe told the offset.A single large offset MAY be an indication that a hunk was installed in thewrong place.You will also be told if a fuzz factor was used to make the match, in whichcase you should also be slightly suspicious..PPIf no original file is specified on the command line,.I patchwill try to figure out from the leading garbage what the name of the fileto edit is.In the header of a context diff, the filename is found from lines beginningwith \*(L"***\*(R" or \*(L"---\*(R", with the shortest name of an existingfile winning.Only context diffs have lines like that, but if there is an \*(L"Index:\*(R"line in the leading garbage,.I patchwill try to use the filename from that line.The context diff header takes precedence over an Index line.If no filename can be intuited from the leading garbage, you will be askedfor the name of the file to patch..PP(If the original file cannot be found, but a suitable SCCS or RCS file ishandy,.I patchwill attempt to get or check out the file.).PPAdditionally, if the leading garbage contains a \*(L"Prereq: \*(R" line,.I patchwill take the first word from the prerequisites line (normally a versionnumber) and check the input file to see if that word can be found.If not,.I patchwill ask for confirmation before proceeding..PPThe upshot of all this is that you should be able to say, while in a newsinterface, the following:.Sp	| patch -d /usr/src/local/blurfl.Spand patch a file in the blurfl directory directly from the article containingthe patch..PPIf the patch file contains more than one patch,.I patchwill try to apply each of them as if they came from separate patch files.This means, among other things, that it is assumed that the name of the fileto patch must be determined for each diff listing,and that the garbage before each diff listing willbe examined for interesting things such as filenames and revision level, asmentioned previously.You can give switches (and another original file name) for the second andsubsequent patches by separating the corresponding argument listsby a \*(L'+\*(R'.(The argument list for a second or subsequent patch may not specify a newpatch file, however.).PP.I Patchrecognizes the following switches:.TP 5.B \-bcauses the next argument to be interpreted as the backup extension, to beused in place of \*(L".orig\*(R"..TP 5.B \-cforces.I patchto interpret the patch file as a context diff..TP 5.B \-dcauses.I patchto interpret the next argument as a directory, and cd to it before doinganything else..TP 5.B \-Dcauses.I patchto use the "#ifdef...#endif" construct to mark changes.The argument following will be used as the differentiating symbol.Note that, unlike the C compiler, there must be a space between the.B \-Dand the argument..TP 5.B \-eforces.I patchto interpret the patch file as an ed script..TP 5.B \-fforces.I patchto assume that the user knows exactly what he or she is doing, and to notask any questions.It does not suppress commentary, however.Use.B \-sfor that..TP 5.B \-F<number>sets the maximum fuzz factor.This switch only applied to context diffs, and causes.I patchto ignore up to that many lines in looking for places to install a hunk.Note that a larger fuzz factor increases the odds of a faulty patch.The default fuzz factor is 2, and it may not be set to more thanthe number of lines of context in the context diff, ordinarily 3..TP 5.B \-lcauses the pattern matching to be done loosely, in case the tabs andspaces have been munged in your input file.Any sequence of whitespace in the pattern line will match any sequencein the input file.Normal characters must still match exactly.Each line of the context must still match a line in the input file..TP 5.B \-nforces.I patchto interpret the patch file as a normal diff..TP 5.B \-Ncauses.I patchto ignore patches that it thinks are reversed or already applied.See also.B \-R ..TP 5.B \-ocauses the next argument to be interpreted as the output file name..TP 5.B \-p<number>sets the pathname strip count,which controls how pathnames found in the patch file are treated, in casethe you keep your files in a different directory than the person who sentout the patch.The strip count specifies how many backslashes are to be stripped fromthe front of the pathname.(Any intervening directory names also go away.)For example, supposing the filename in the patch file was.sp	/u/howard/src/blurfl/blurfl.c.spsetting.B \-por.B \-p0gives the entire pathname unmodified,.B \-p1gives.sp	u/howard/src/blurfl/blurfl.c.spwithout the leading slash,.B \-p4gives.sp	blurfl/blurfl.c.spand not specifying.B \-pat all just gives you "blurfl.c".Whatever you end up with is looked for either in the current directory,or the directory specified by the.B \-dswitch..TP 5.B \-rcauses the next argument to be interpreted as the reject file name..TP 5.B \-Rtells.I patchthat this patch was created with the old and new files swapped.(Yes, I'm afraid that does happen occasionally, human nature being what itis.).I Patchwill attempt to swap each hunk around before applying it.Rejects will come out in the swapped format.The.B \-Rswitch will not work with ed diff scripts because there is too littleinformation to reconstruct the reverse operation..SpIf the first hunk of a patch fails,.I patchwill reverse the hunk to see if it can be applied that way.If it can, you will be asked if you want to have the.B \-Rswitch set.If it can't, the patch will continue to be applied normally.(Note: this method cannot detect a reversed patch if it is a normal diffand if the first command is an append (i.e. it should have been a delete)since appends always succeed, due to the fact that a null context will matchanywhere.Luckily, most patches add or change lines rather than delete them, so mostreversed normal diffs will begin with a delete, which will fail, triggeringthe heuristic.).TP 5.B \-smakes.I patchdo its work silently, unless an error occurs..TP 5.B \-Scauses.I patchto ignore this patch from the patch file, but continue on lookingfor the next patch in the file.Thus.sp	patch -S + -S + <patchfile.spwill ignore the first and second of three patches..TP 5.B \-vcauses.I patchto print out it's revision header and patch level..TP 5.B \-x<number>sets internal debugging flags, and is of interest only to.I patchpatchers..SH ENVIRONMENTNo environment variables are used by.IR patch ..SH FILES/tmp/patch*.SH SEE ALSOdiff(1).SH NOTES FOR PATCH SENDERSThere are several things you should bear in mind if you are going tobe sending out patches.First, you can save people a lot of grief by keeping a patchlevel.h filewhich is patched to increment the patch level as the first diff in thepatch file you send out.If you put a Prereq: line in with the patch, it won't let them applypatches out of order without some warning.Second, make sure you've specified the filenames right, either in acontext diff header, or with an Index: line.If you are patching something in a subdirectory, be sure to tell the patchuser to specify a .B \-pswitch as needed.Third, you can create a file by sending out a diff that compares anull file to the file you want to create.This will only work if the file you want to create doesn't exist already inthe target directory.Fourth, take care not to send out reversed patches, since it makes people wonderwhether they already applied the patch.Fifth, while you may be able to get away with putting 582 diff listings intoone file, it is probably wiser to group related patches into separate files incase something goes haywire..SH DIAGNOSTICSToo many to list here, but generally indicative that.I patchcouldn't parse your patch file..PPThe message \*(L"Hmm...\*(R" indicates that there is unprocessed text inthe patch file and that.I patchis attempting to intuit whether there is a patch in that text and, if so,what kind of patch it is..SH CAVEATS.I Patchcannot tell if the line numbers are off in an ed script, and can only detectbad line numbers in a normal diff when it finds a \*(L"change\*(R" ora \*(L"delete\*(R" command.A context diff using fuzz factor 3 may have the same problem.Until a suitable interactive interface is added, you should probably doa context diff in these cases to see if the changes made sense.Of course, compiling without errors is a pretty good indication that the patchworked, but not always..PP.I Patchusually produces the correct results, even when it has to do a lot ofguessing.However, the results are guaranteed to be correct only when the patch isapplied to exactly the same version of the file that the patch wasgenerated from..SH BUGSCould be smarter about partial matches, excessively \&deviant offsets andswapped code, but that would take an extra pass..PPIf code has been duplicated (for instance with #ifdef OLDCODE ... #else ...#endif),.I patchis incapable of patching both versions, and, if it works at all, will likelypatch the wrong one, and tell you that it succeeded to boot..PPIf you apply a patch you've already applied,.I patchwill think it is a reversed patch, and offer to un-apply the patch.This could be construed as a feature.