patch.1

这是一个同样来自贝尔实验室的和UNIX有着渊源的操作系统, 其简洁的设计和实现易于我们学习和理解

.\" patch man page
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.TH PATCH 1 \*(Dt GNU
.ta 3n
.SH NAME
patch \- apply a diff file to an original
.SH SYNOPSIS
.B patch
.RI [ options ]
.RI [ originalfile
.RI [ patchfile ]]
.Sp
but usually just
.Sp
.BI "patch \-p" "num"
.BI < patchfile
.SH DESCRIPTION
.B patch
takes a patch file
.I patchfile
containing a difference listing produced by the
.B diff
program and applies those differences to one or more original files,
producing patched versions.
Normally the patched versions are put in place of the originals.
Backups can be made; see the
.B \-b
or
.B \*=backup
option.
The names of the files to be patched are usually taken from the patch file,
but if there's just one file to be patched it can specified on the
command line as
.IR originalfile .
.PP
Upon startup, patch attempts to determine the type of the diff listing,
unless overruled by a
\fB\-c\fP (\fB\*=context\fP),
\fB\-e\fP (\fB\*=ed\fP),
\fB\-n\fP (\fB\*=normal\fP),
or
\fB\-u\fP (\fB\*=unified\fP)
option.
Context diffs (old-style, new-style, and unified) and
normal diffs are applied by the
.B patch
program itself, while
.B ed
diffs are simply fed to the
.BR ed (1)
editor via a pipe.
.PP
.B patch
tries to skip any leading garbage, apply the diff,
and then skip any trailing garbage.
Thus you could feed an article or message containing a
diff listing to
.BR patch ,
and it should work.
If the entire diff is indented by a consistent amount,
or if a context diff is encapsulated one or more times by prepending
"\fB\- \fP" to lines starting with "\fB\-\fP" as specified by Internet RFC 934,
this is taken into account.
.PP
With context diffs, and to a lesser extent with normal diffs,
.B patch
can detect when the line numbers mentioned in the patch are incorrect,
and attempts 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 or
minus any offset used in applying the previous hunk.
If that is not the correct place,
.B patch
scans both forwards and backwards for a set of lines matching the context
given in the hunk.
First
.B patch
looks 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 factor
is set to 1 or more, then another scan takes place ignoring the first and last
line 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
.B patch
cannot find a place to install that hunk of the patch, it puts the
hunk out to a reject file, which normally is the name of the output file
plus a
.B \&.rej
suffix, or
.B #
if
.B \&.rej
would generate a file name that is too long
(if even appending the single character
.B #
makes the file name too long, then
.B #
replaces the file name's last character).
(The rejected hunk comes out in ordinary context diff form regardless of
the input patch's form.
If the input was a normal diff, many of the contexts are simply null.)
The line numbers on the hunks in the reject file may be different than
in the patch file: they reflect the approximate location patch thinks the
failed hunks belong in the new file rather than the old one.
.PP
As each hunk is completed, you are told if the hunk
failed, and if so which line (in the new file)
.B patch
thought the hunk should go on.
If the hunk is installed at a different line
from the line number specified in the diff you
are told the offset.
A single large offset
.I may
indicate that a hunk was installed in the
wrong place.
You are also told if a fuzz factor was used to make the match, in which
case you should also be slightly suspicious.
If the
.B \*=verbose
option is given, you are also told about hunks that match exactly.
.PP
If no original file
.I origfile
is specified on the command line,
.B patch
tries to figure out from the leading garbage what the name of the file
to edit is, using the following rules.
.TP 3
.B " \(bu"
If the header is that of a context diff,
.B patch
takes the old and new file names in the header.
Any
.B /dev/null
names are ignored.
.TP
.B " \(bu"
If there is an
.B Index:\&
line in the leading garbage
and if either the old and new names are both absent or the
.B POSIXLY_CORRECT
environment variable is set,
.B patch
takes the name in the
.B Index:\&
line.
.TP
.B " \(bu"
For the purpose of the following rules,
the names are considered to be in the order (old, new, index),
regardless of the order that they appear in the header.
.TP
.B " \(bu"
If some of the named files exist,
.B patch
uses the first name if the
.B POSIXLY_CORRECT
environment variable is set, and the best name otherwise.
.TP
.B " \(bu"
If
.B patch
is not ignoring \s-1RCS\s0 and \s-1SCCS\s0 (see the
.BI "\-g\ " num
or
.BI \*=get= num
option), and no named files exist
but an \s-1RCS\s0 or \s-1SCCS\s0 master is found,
.B patch
uses the first named file with an \s-1RCS\s0 or \s-1SCCS\s0 master.
.TP
.B " \(bu"
If no named files exist, no \s-1RCS\s0 or \s-1SCCS\s0 master was found,
some names are given,
.B POSIXLY_CORRECT
is not set, and the patch appears to create a file,
.B patch
uses the best name requiring the creation of the fewest directories.
.TP
.B " \(bu"
If no file name results from the above heuristics, you are asked
for the name of the file to patch.
.LP
To determine the
.I best
of a nonempty list of file names,
.B patch
first takes all the names with the fewest path name components;
of those, it then takes all the names with the shortest basename;
of those, it then takes all the shortest names;
finally, it takes the first remaining name.
.PP
Additionally, if the leading garbage contains a
.B Prereq:\&
line,
.B patch
takes the first word from the prerequisites line (normally a version
number) and checks the original file to see if that word can be found.
If not,
.B patch
asks for confirmation before proceeding.
.PP
The upshot of all this is that you should be able to say, while in a news
interface, something like the following:
.Sp
	\fB| patch \-d /usr/src/local/blurfl\fP
.Sp
and patch a file in the
.B blurfl
directory directly from the article containing
the patch.
.PP
If the patch file contains more than one patch,
.B patch
tries 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 file
to patch must be determined for each diff listing,
and that the garbage before each diff listing
contains interesting things such as file names and revision level, as
mentioned previously.
.SH OPTIONS
.TP 3
\fB\-b\fP  or  \fB\*=backup\fP
Make backup files.
That is, when patching a file,
rename or copy the original instead of removing it.
When backing up a file that does not exist,
an empty, unreadable backup file is created
as a placeholder to represent the nonexistent file.
See the
.B \-V
or
.B \*=version\-control
option for details about how backup file names are determined.
.TP
.B \*=backup\-if\-mismatch
Back up a file if the patch does not match the file exactly
and if backups are not otherwise requested.
This is the default unless the
.B POSIXLY_CORRECT
environment variable is set.
.TP
.B \*=no\-backup\-if\-mismatch
Do not back up a file if the patch does not match the file exactly
and if backups are not otherwise requested.
This is the default if the
.B POSIXLY_CORRECT
environment variable is set.
.TP
\fB\-B\fP \fIpref\fP  or  \fB\*=prefix=\fP\fIpref\fP
Prefix
.I pref
to a file name when generating its simple backup file name.
For example, with
.B "\-B\ /junk/"
the simple backup file name for
.B src/patch/util.c
is
.BR /junk/src/patch/util.c .
.TP
\fB\*=binary\fP
Read and write all files in binary mode,
except for standard output and
.BR /dev/tty .
This option has no effect on \s-1POSIX\s0-compliant systems.
On systems like \s-1DOS\s0 where this option makes a difference,
the patch should be generated by
.BR "diff\ \-a\ \*=binary" .
.TP
\fB\-c\fP  or  \fB\*=context\fP
Interpret the patch file as a ordinary context diff.
.TP
\fB\-d\fP \fIdir\fP  or  \fB\*=directory=\fP\fIdir\fP
Change to the directory
.I dir
immediately, before doing
anything else.
.TP
\fB\-D\fP \fIdefine\fP  or  \fB\*=ifdef=\fP\fIdefine\fP
Use the
.BR #ifdef " .\|.\|. " #endif
construct to mark changes, with
.I define
as the differentiating symbol.
.TP
.B "\*=dry\-run"
Print the results of applying the patches without actually changing any files.
.TP
\fB\-e\fP  or  \fB\*=ed\fP
Interpret the patch file as an
.B ed
script.
.TP
\fB\-E\fP  or  \fB\*=remove\-empty\-files\fP
Remove output files that are empty after the patches have been applied.
Normally this option is unnecessary, since
.B patch
can examine the time stamps on the header to determine whether a file
should exist after patching.
However, if the input is not a context diff or if the
.B POSIXLY_CORRECT
environment variable is set,
.B patch
does not remove empty patched files unless this option is given.
When
.B patch
removes a file, it also attempts to remove any empty ancestor directories.
.TP
\fB\-f\fP  or  \fB\*=force\fP
Assume that the user knows exactly what he or she is doing, and do not
ask any questions.  Skip patches whose headers
do not say which file is to be patched; patch files even though they have the
wrong version for the
.B Prereq:\&
line in the patch; and assume that
patches are not reversed even if they look like they are.
This option does not suppress commentary; use
.B \-s
for that.
.TP
\fB\-F\fP \fInum\fP  or  \fB\*=fuzz=\fP\fInum\fP
Set the maximum fuzz factor.
This option only applies to diffs that have context, and causes
.B patch
to 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 than
the number of lines of context in the context diff, ordinarily 3.
.TP
\fB\-g\fP \fInum\fP  or  \fB\*=get=\fP\fInum\fP
This option controls
.BR patch 's
actions when a file is under \s-1RCS\s0 or \s-1SCCS\s0 control,
and does not exist or is read-only and matches the default version.
If
.I num
is positive,
.B patch
gets (or checks out) the file from the revision control system; if zero,
.B patch
ignores \s-1RCS\s0 and \s-1SCCS\s0 and does not get the file; and if negative,
.B patch
asks the user whether to get the file.
The default value of this option is given by the value of the
.B PATCH_GET
environment variable if it is set; if not, the default value is zero if 
.B POSIXLY_CORRECT
is set, negative otherwise.
.TP
.B "\*=help"
Print a summary of options and exit.
.TP
\fB\-i\fP \fIpatchfile\fP  or  \fB\*=input=\fP\fIpatchfile\fP
Read the patch from
.IR patchfile .
If
.I patchfile
is
.BR \- ,
read from standard input, the default.
.TP
\fB\-l\fP  or  \fB\*=ignore\-whitespace\fP
Match patterns loosely, in case tabs or spaces
have been munged in your files.
Any sequence of one or more blanks in the patch file matches any sequence
in the original file, and sequences of blanks at the ends of lines are ignored.
Normal characters must still match exactly.
Each line of the context must still match a line in the original file.
.TP
\fB\-n\fP  or  \fB\*=normal\fP
Interpret the patch file as a normal diff.
.TP
\fB\-N\fP  or  \fB\*=forward\fP
Ignore patches that seem to be reversed or already applied.
See also
.BR \-R .
.TP
\fB\-o\fP \fIoutfile\fP  or  \fB\*=output=\fP\fIoutfile\fP
Send output to
.I outfile
instead of patching files in place.
.TP
\fB\-p\fP\fInum\fP  or  \fB\*=strip\fP\fB=\fP\fInum\fP
Strip the smallest prefix containing
.I num
leading slashes from each file name found in the patch file.
A sequence of one or more adjacent slashes is counted as a single slash.
This controls how file names found in the patch file are treated, in case
you keep your files in a different directory than the person who sent
out the patch.
For example, supposing the file name in the patch file was
.Sp
	\fB/u/howard/src/blurfl/blurfl.c\fP
.Sp
setting
.B \-p0
gives the entire file name unmodified,
.B \-p1
gives
.Sp
	\fBu/howard/src/blurfl/blurfl.c\fP
.Sp
without the leading slash,
.B \-p4
gives
.Sp
	\fBblurfl/blurfl.c\fP
.Sp
and not specifying
.B \-p
at all just gives you \fBblurfl.c\fP.
Whatever you end up with is looked for either in the current directory,
or the directory specified by the
.B \-d
option.
.TP
\fB\-r\fP \fIrejectfile\fP  or  \fB\*=reject\-file=\fP\fIrejectfile\fP
Put rejects into
.I rejectfile
instead of the default
.B \&.rej
file.
.TP
\fB\-R\fP  or  \fB\*=reverse\fP
Assume that this patch was created with the old and new files swapped.
(Yes, I'm afraid that does happen occasionally, human nature being what it
is.)
.B patch
attempts to swap each hunk around before applying it.
Rejects come out in the swapped format.
The
.B \-R
option does not work with
.B ed
diff scripts because there is too little
information to reconstruct the reverse operation.
.Sp
If the first hunk of a patch fails,
.B patch
reverses the hunk to see if it can be applied that way.
If it can, you are asked if you want to have the
.B \-R
option set.
If it can't, the patch continues to be applied normally.
(Note: this method cannot detect a reversed patch if it is a normal diff
and 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 matches
anywhere.
Luckily, most patches add or change lines rather than delete them, so most
reversed normal diffs begin with a delete, which fails, triggering
the heuristic.)
.TP
\fB\-s\fP  or  \fB\*=silent\fP  or  \fB\*=quiet\fP
Work silently, unless an error occurs.
.TP
\fB\-t\fP  or  \fB\*=batch\fP
Suppress questions like
.BR \-f ,
but make some different assumptions:
skip patches whose headers do not contain file names (the same as \fB\-f\fP);
skip patches for which the file has the wrong version for the
.B Prereq:\&
line
in the patch; and assume that patches are reversed if they look like
they are.
.TP
\fB\-T\fP  or  \fB\*=set\-time\fP
Set the modification and access times of patched files from time stamps
given in context diff headers, assuming that the context diff headers
use local time.  This option is not recommended, because patches using
local time cannot easily be used by people in other time zones, and
because local time stamps are ambiguous when local clocks move backwards
during daylight-saving time adjustments.  Instead of using this option,
generate patches with \s-1UTC\s0 and use the
.B \-Z
or
.B \*=set\-utc
option instead.
.TP
\fB\-u\fP  or  \fB\*=unified\fP
Interpret the patch file as a unified context diff.
.TP
\fB\-v\fP  or  \fB\*=version\fP
Print out
.BR patch 's
revision header and patch level, and exit.
.TP
\fB\-V\fP \fImethod\fP  or  \fB\*=version\-control=\fP\fImethod\fP
Use
.I method
to determine
backup file names.  The method can also be given by the
.B PATCH_VERSION_CONTROL
(or, if that's not set, the
.BR VERSION_CONTROL )
environment variable, which is overridden by this option.
The method does not affect whether backup files are made;
it affects only the names of any backup files that are made.
.Sp
The value of
.I method
is like the \s-1GNU\s0
Emacs `version-control' variable;
.B patch
also recognizes synonyms that
are more descriptive.  The valid values for
.I method
are (unique abbreviations are
accepted):
.RS
.TP 3
\fBexisting\fP  or  \fBnil\fP
Make numbered backups of files that already have them,
otherwise simple backups.
This is the default.
.TP
\fBnumbered\fP  or  \fBt\fP
Make numbered backups.  The numbered backup file name for
.I F
is
.IB F .~ N ~