patch.man

早期freebsd实现

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'\" Revision 2.0.1.2  88/06/22  20:47:18  lwall
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'\" Revision 2.0  86/09/17  15:39:09  lwall
'\" Baseline for netwide release.
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.de Sh
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.ne 5
.PP
\fB\\$1\fR
.PP
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.TH PATCH 1 LOCAL
.SH NAME
patch - apply a diff file to an original
.SH SYNOPSIS
.B patch
[options] [origfile [patchfile]] [+ [options] [origfile]]...
.sp
but usually just
.sp
.B patch
<patchfile
.SH DESCRIPTION
.I Patch
will take a patch file containing any of the four forms of difference
listing produced by the
.I diff
program and apply those differences to an original file, producing a patched
version.
By default, the patched version is put in place of the original, with
the original file backed up to the same name with the
extension \*(L".orig\*(R" (\*(L"~\*(R" on systems that do not
support long filenames), or as specified by the
.BR -b ,
.BR -B ,
or
.B -V
switches.
The extension used for making backup files may also be specified in the
.B SIMPLE_BACKUP_SUFFIX
environment variable, which is overridden by above switches.
.PP
If the backup file already exists,
.B patch
creates a new backup file name by changing the first lowercase letter
in the last component of the file's name into uppercase.  If there are
no more lowercase letters in the name, it removes the first character
from the name.  It repeats this process until it comes up with a
backup file that does not already exist.
.PP
You may also specify where you want the output to go with a
.B -o
switch; if that file already exists, it is backed up first.
.PP
If
.I patchfile
is omitted, or is a hyphen, the patch will be read from standard input.
.PP
Upon startup, patch will attempt to determine the type of the diff listing,
unless over-ruled by a
.BR -c ,
.BR -e ,
.BR -n ,
or
.B -u
switch.
Context diffs (old-style, new-style, and unified) and
normal diffs are applied by the
.I patch
program itself, while ed diffs are simply fed to the
.I ed
editor via a pipe.
.PP
.I Patch
will try 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
.IR patch ,
and it should work.
If the entire diff is indented by a consistent amount,
this will be taken into account.
.PP
With context diffs, and to a lesser extent with normal diffs,
.I patch
can 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 or
minus any offset used in applying the previous hunk.
If that is not the correct place,
.I patch
will scan both forwards and backwards for a set of lines matching the context
given in the hunk.
First
.I 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
.I patch
cannot find a place to install that hunk of the patch, it will put the
hunk out to a reject file, which normally is the name of the output file
plus \*(L".rej\*(R" (\*(L"#\*(R" on systems that do not support
long filenames).
(Note that the rejected hunk will come out in context diff form whether the
input 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 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 will be told whether the hunk succeeded or
failed, and which line (in the new file)
.I patch
thought the hunk should go on.
If this is different from the line number specified in the diff you will
be told the offset.
A single large offset MAY be an indication that a hunk was installed in the
wrong place.
You will also be told if a fuzz factor was used to make the match, in which
case you should also be slightly suspicious.
.PP
If no original file is specified on the command line,
.I patch
will try to figure out from the leading garbage what the name of the file
to edit is.
In the header of a context diff, the filename is found from lines beginning
with \*(L"***\*(R" or \*(L"---\*(R", with the shortest name of an existing
file winning.
Only context diffs have lines like that, but if there is an \*(L"Index:\*(R"
line in the leading garbage,
.I patch
will 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 asked
for the name of the file to patch.
.PP
If the original file cannot be found or is read-only, but a suitable
SCCS or RCS file is handy,
.I patch
will attempt to get or check out the file.
.PP
Additionally, if the leading garbage contains a \*(L"Prereq: \*(R" line,
.I patch
will take the first word from the prerequisites line (normally a version
number) and check the input file to see if that word can be found.
If not,
.I patch
will ask for confirmation before proceeding.
.PP
The upshot of all this is that you should be able to say, while in a news
interface, the following:
.Sp
	| patch -d /usr/src/local/blurfl
.Sp
and patch a file in the blurfl directory directly from the article containing
the patch.
.PP
If the patch file contains more than one patch,
.I patch
will 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 file
to patch must be determined for each diff listing,
and that the garbage before each diff listing will
be examined for interesting things such as filenames and revision level, as
mentioned previously.
You can give switches (and another original file name) for the second and
subsequent patches by separating the corresponding argument lists
by a \*(L'+\*(R'.
(The argument list for a second or subsequent patch may not specify a new
patch file, however.)
.PP
.I Patch
recognizes the following switches:
.TP 5
.B \-b
causes the next argument to be interpreted as the backup extension, to be
used in place of \*(L".orig\*(R" or \*(L"~\*(R".
.TP 5
.B \-B
causes the next argument to be interpreted as a prefix to the backup file
name. If this argument is specified any argument from -b will be ignored.
.TP 5
.B \-c
forces
.I patch
to interpret the patch file as a context diff.
.TP 5
.B \-d
causes
.I patch
to interpret the next argument as a directory, and cd to it before doing
anything else.
.TP 5
.B \-D
causes
.I patch
to 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 \-D
and the argument.
.TP 5
.B \-e
forces
.I patch
to interpret the patch file as an ed script.
.TP 5
.B \-E
causes
.I patch