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

where
.I N
is the version number.
.TP
\fBsimple\fP  or  \fBnever\fP
Make simple backups.
The
.B \-B
or
.BR \*=prefix ,
.B \-Y
or
.BR \*=basename\-prefix ,
and
.B \-z
or
.BR \*=suffix
options specify the simple backup file name.
If none of these options are given, then a simple backup suffix is used;
it is the value of the
.B SIMPLE_BACKUP_SUFFIX
environment variable if set, and is
.B \&.orig
otherwise.
.PP
With numbered or simple backups,
if the backup file name is too long, the backup suffix
.B ~
is used instead; if even appending
.B ~
would make the name too long, then
.B ~
replaces the last character of the file name.
.RE
.TP
\fB\*=verbose\fP
Output extra information about the work being done.
.TP
\fB\-x\fP \fInum\fP  or  \fB\*=debug=\fP\fInum\fP
Set internal debugging flags of interest only to
.B patch
patchers.
.TP
\fB\-Y\fP \fIpref\fP  or  \fB\*=basename\-prefix=\fP\fIpref\fP
Prefix
.I pref
to the basename of a file name when generating its simple backup file name.
For example, with
.B "\-Y\ .del/"
the simple backup file name for
.B src/patch/util.c
is
.BR src/patch/.del/util.c .
.TP
\fB\-z\fP \fIsuffix\fP  or  \fB\*=suffix=\fP\fIsuffix\fP
Use
.I suffix
as the simple backup suffix.
For example, with
.B "\-z\ -"
the simple backup file name for
.B src/patch/util.c
is
.BR src/patch/util.c- .
The backup suffix may also be specified by the
.B SIMPLE_BACKUP_SUFFIX
environment variable, which is overridden by this option.
.TP
\fB\-Z\fP  or  \fB\*=set\-utc\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 Coordinated Universal Time (\s-1UTC\s0, often known as \s-1GMT\s0).
Also see the
.B \-T
or
.B \*=set\-time
option.
.Sp
The
.B \-Z
or
.B \*=set\-utc
and
.B \-T
or
.B \*=set\-time
options normally refrain from setting a file's time if the file's original time
does not match the time given in the patch header, or if its
contents do not match the patch exactly.  However, if the
.B \-f
or
.B \*=force
option is given, the file time is set regardless.
.Sp
Due to the limitations of
.B diff
output format, these options cannot update the times of files whose
contents have not changed.  Also, if you use these options, you should remove
(e.g. with
.BR "make\ clean" )
all files that depend on the patched files, so that later invocations of
.B make
do not get confused by the patched files' times.
.SH ENVIRONMENT
.TP 3
\fBPATCH_GET\fP
This specifies whether
.B patch
gets missing or read-only files from \s-1RCS\s0 or \s-1SCCS\s0
by default; see the
.B \-g
or
.B \*=get
option.
.TP
.B POSIXLY_CORRECT
If set,
.B patch
conforms more strictly to the \s-1POSIX\s0 standard:
it takes the first existing file from the list (old, new, index)
when intuiting file names from diff headers,
it does not remove files that are empty after patching,
it does not ask whether to get files from \s-1RCS\s0 or \s-1SCCS\s0,
it requires that all options precede the files in the command line,
and it does not backup files when there is a mismatch.
.TP
.B SIMPLE_BACKUP_SUFFIX
Extension to use for simple backup file names instead of
.BR \&.orig .
.TP
\fBTMPDIR\fP, \fBTMP\fP, \fBTEMP\fP
Directory to put temporary files in;
.B patch
uses the first environment variable in this list that is set.
If none are set, the default is system-dependent;
it is normally
.B /tmp
on Unix hosts.
.TP
\fBVERSION_CONTROL\fP or \fBPATCH_VERSION_CONTROL\fP
Selects version control style; see the
.B \-v
or
.B \*=version\-control
option.
.SH FILES
.TP 3
.IB $TMPDIR "/p\(**"
temporary files
.TP
.B /dev/tty
controlling terminal; used to get answers to questions asked of the user
.SH "SEE ALSO"
.BR diff (1),
.BR ed (1)
.Sp
Marshall T. Rose and Einar A. Stefferud,
Proposed Standard for Message Encapsulation,
Internet RFC 934 <URL:ftp://ftp.isi.edu/in-notes/rfc934.txt> (1985-01).
.SH "NOTES FOR PATCH SENDERS"
There are several things you should bear in mind if you are going to
be sending out patches.
.PP
Create your patch systematically.
A good method is the command
.BI "diff\ \-Naur\ " "old\ new"
where
.I old
and
.I new
identify the old and new directories.
The names
.I old
and
.I new
should not contain any slashes.
The
.B diff
command's headers should have dates
and times in Universal Time using traditional Unix format,
so that patch recipients can use the
.B \-Z
or
.B \*=set\-utc
option.
Here is an example command, using Bourne shell syntax:
.Sp
	\fBLC_ALL=C TZ=UTC0 diff \-Naur gcc\-2.7 gcc\-2.8\fP
.PP
Tell your recipients how to apply the patch
by telling them which directory to
.B cd
to, and which
.B patch
options to use.  The option string
.B "\-Np1"
is recommended.
Test your procedure by pretending to be a recipient and applying
your patch to a copy of the original files.
.PP
You can save people a lot of grief by keeping a
.B patchlevel.h
file which is patched to increment the patch level
as the first diff in the patch file you send out.
If you put a
.B Prereq:\&
line in with the patch, it won't let them apply
patches out of order without some warning.
.PP
You can create a file by sending out a diff that compares
.B /dev/null
or an empty file dated the Epoch (1970-01-01 00:00:00 \s-1UTC\s0)
to the file you want to create.
This only works if the file you want to create doesn't exist already in
the target directory.
Conversely, you can remove a file by sending out a context diff that compares
the file to be deleted with an empty file dated the Epoch.
The file will be removed unless the
.B POSIXLY_CORRECT
environment variable is set and the
.B \-E
or
.B \*=remove\-empty\-files
option is not given.
An easy way to generate patches that create and remove files
is to use \s-1GNU\s0
.BR diff 's
.B \-N
or
.B \*=new\-file
option.
.PP
If the recipient is supposed to use the
.BI \-p N
option, do not send output that looks like this:
.Sp
.ft B
.ne 3
	diff \-Naur v2.0.29/prog/README prog/README
.br
	\-\^\-\^\- v2.0.29/prog/README   Mon Mar 10 15:13:12 1997
.br
	+\^+\^+ prog/README   Mon Mar 17 14:58:22 1997
.ft
.Sp
because the two file names have different numbers of slashes,
and different versions of
.B patch
interpret the file names differently.
To avoid confusion, send output that looks like this instead:
.Sp
.ft B
.ne 3
	diff \-Naur v2.0.29/prog/README v2.0.30/prog/README
.br
	\-\^\-\^\- v2.0.29/prog/README   Mon Mar 10 15:13:12 1997
.br
	+\^+\^+ v2.0.30/prog/README   Mon Mar 17 14:58:22 1997
.ft
.Sp
.PP
Avoid sending patches that compare backup file names like
.BR README.orig ,
since this might confuse
.B patch
into patching a backup file instead of the real file.
Instead, send patches that compare the same base file names
in different directories, e.g.\&
.B old/README
and
.BR new/README .
.PP
Take care not to send out reversed patches, since it makes people wonder
whether they already applied the patch.
.PP
Try not to have your patch modify derived files
(e.g. the file
.B configure
where there is a line
.B "configure: configure.in"
in your makefile), since the recipient should be
able to regenerate the derived files anyway.
If you must send diffs of derived files,
generate the diffs using \s-1UTC\s0,
have the recipients apply the patch with the
.B \-Z
or
.B \*=set\-utc
option, and have them remove any unpatched files that depend on patched files
(e.g. with
.BR "make\ clean" ).
.PP
While you may be able to get away with putting 582 diff listings into
one file, it may be wiser to group related patches into separate files in
case something goes haywire.
.SH DIAGNOSTICS
Diagnostics generally indicate that
.B patch
couldn't parse your patch file.
.PP
If the
.B \*=verbose
option is given, the message
.B Hmm.\|.\|.\&
indicates that there is unprocessed text in
the patch file and that
.B patch
is attempting to intuit whether there is a patch in that text and, if so,
what kind of patch it is.
.PP
.BR patch 's
exit status is
0 if all hunks are applied successfully,
1 if some hunks cannot be applied,
and 2 if there is more serious trouble.
When applying a set of patches in a loop it behooves you to check this
exit status so you don't apply a later patch to a partially patched file.
.SH CAVEATS
Context diffs cannot reliably represent the creation or deletion of
empty files, empty directories, or special files such as symbolic links.
Nor can they represent changes to file metadata like ownership, permissions,
or whether one file is a hard link to another.
If changes like these are also required, separate instructions
(e.g. a shell script) to accomplish them should accompany the patch.
.PP
.B patch
cannot tell if the line numbers are off in an
.B ed
script, and can detect
bad line numbers in a normal diff only when it finds a change or deletion.
A context diff using fuzz factor 3 may have the same problem.
Until a suitable interactive interface is added, you should probably do
a context diff in these cases to see if the changes made sense.
Of course, compiling without errors is a pretty good indication that the patch
worked, but not always.
.PP
.B patch
usually produces the correct results, even when it has to do a lot of
guessing.
However, the results are guaranteed to be correct only when the patch is
applied to exactly the same version of the file that the patch was
generated from.
.SH "COMPATIBILITY ISSUES"
The \s-1POSIX\s0 standard specifies behavior that differs from
.BR patch 's
traditional behavior.
You should be aware of these differences if you must interoperate with
.B patch
versions 2.1 and earlier, which are not \s-1POSIX\s0-compliant.
.TP 3
.B " \(bu"
In traditional
.BR patch ,
the
.B \-p
option's operand was optional, and a bare
.B \-p
was equivalent to
.BR \-p0.
The
.B \-p
option now requires an operand, and
.B "\-p\ 0"
is now equivalent to
.BR \-p0 .
For maximum compatibility, use options like
.B \-p0
and
.BR \-p1 .
.Sp
Also,
traditional
.B patch
simply counted slashes when stripping path prefixes;
.B patch
now counts pathname components.
That is, a sequence of one or more adjacent slashes
now counts as a single slash.
For maximum portability, avoid sending patches containing
.B //
in file names.
.TP
.B " \(bu"
In traditional
.BR patch ,
backups were enabled by default.
This behavior is now enabled with the
.B \-b
or
.B \*=backup
option.
.Sp
Conversely, in \s-1POSIX\s0
.BR patch ,
backups are never made, even when there is a mismatch.
In \s-1GNU\s0
.BR patch ,
this behavior is enabled with the
.B \*=no\-backup\-if\-mismatch
option or by setting the
.B POSIXLY_CORRECT
environment variable.
.Sp
The
.BI \-b "\ suffix"
option
of traditional
.B patch
is equivalent to the
.BI "\-b\ \-z" "\ suffix"
options of \s-1GNU\s0
.BR patch .
.TP
.B " \(bu"
Traditional
.B patch
used a complicated (and incompletely documented) method
to intuit the name of the file to be patched from the patch header.
This method was not \s-1POSIX\s0-compliant, and had a few gotchas.
Now
.B patch
uses a different, equally complicated (but better documented) method
that is optionally \s-1POSIX\s0-compliant; we hope it has
fewer gotchas.  The two methods are compatible if the
file names in the context diff header and the
.B Index:\&
line are all identical after prefix-stripping.
Your patch is normally compatible if each header's file names
all contain the same number of slashes.
.TP
.B " \(bu"
When traditional
.B patch
asked the user a question, it sent the question to standard error
and looked for an answer from
the first file in the following list that was a terminal:
standard error, standard output,
.BR /dev/tty ,
and standard input.
Now
.B patch
sends questions to standard output and gets answers from
.BR /dev/tty .
Defaults for some answers have been changed so that
.B patch
never goes into an infinite loop when using default answers.
.TP
.B " \(bu"
Traditional
.B patch
exited with a status value that counted the number of bad hunks,
or with status 1 if there was real trouble.
Now
.B patch
exits with status 1 if some hunks failed,
or with 2 if there was real trouble.
.TP
.B " \(bu"
Limit yourself to the following options when sending instructions
meant to be executed by anyone running \s-1GNU\s0
.BR patch ,
traditional
.BR patch ,
or a \s-1POSIX\s0-compliant
.BR patch .
Spaces are significant in the following list, and operands are required.
.Sp
.nf
.in +3
.ne 11
.B \-c
.BI \-d " dir"
.BI \-D " define"
.B \-e
.B \-l
.B \-n
.B \-N
.BI \-o " outfile"
.BI \-p num
.B \-R
.BI \-r " rejectfile"
.in
.fi
.SH BUGS
.B patch
could be smarter about partial matches, excessively deviant offsets and
swapped code, but that would take an extra pass.
.PP
If code has been duplicated (for instance with
\fB#ifdef OLDCODE\fP .\|.\|. \fB#else .\|.\|. #endif\fP),
.B patch
is incapable of patching both versions, and, if it works at all, will likely
patch the wrong one, and tell you that it succeeded to boot.
.PP
If you apply a patch you've already applied,
.B patch
thinks it is a reversed patch, and offers to un-apply the patch.
This could be construed as a feature.
.SH COPYING
Copyright
.if t \(co
1984, 1985, 1986, 1988 Larry Wall.
.br
Copyright
.if t \(co
1997 Free Software Foundation, Inc.
.PP
Permission is granted to make and distribute verbatim copies of
this manual provided the copyright notice and this permission notice
are preserved on all copies.
.PP
Permission is granted to copy and distribute modified versions of this
manual under the conditions for verbatim copying, provided that the
entire resulting derived work is distributed under the terms of a
permission notice identical to this one.
.PP
Permission is granted to copy and distribute translations of this
manual into another language, under the above conditions for modified
versions, except that this permission notice may be included in
translations approved by the copyright holders instead of in
the original English.
.SH AUTHORS
Larry Wall wrote the original version of
.BR patch .
Paul Eggert removed
.BR patch 's
arbitrary limits; added support for binary files,
setting file times, and deleting files;
and made it conform better to \s-1POSIX\s0.
Other contributors include Wayne Davison, who added unidiff support,
and David MacKenzie, who added configuration and backup support.