patch.html

unix 下的C开发手册,还用详细的例程。

A patchfile may contain patching instructions for more than one file;
filenames are determined as specified in
<xref href=patchfd><a href="#tag_001_014_1662_002">
Filename Determination
</a></xref>.
When the
<b>-b</b>
option is specified,
for each patched file, the original will be saved in a
file of the same name with the suffix
<b>.orig</b>
appended to it.
<p>
For each patched file, a reject file may also be created as noted in
<xref href=patchapp><a href="#tag_001_014_1662_003">
Patch Application
</a></xref>.
In the absence of a
<b>-r</b>
option, the name of
this file will be formed by appending the suffix
<b>.rej</b>
to the original filename.
<h5><a name = "tag_001_014_1662_001">&nbsp;</a>Patchfile Format</h5>
The patch file must contain zero or more lines of header information
followed by one or more patches.
Each patch must contain zero or more
lines of filename identification in the format produced by
<i><a href="diff.html">diff</a></i>
<b>-c</b>,
and one or more sets of
<i><a href="diff.html">diff</a></i>
output, which are customarily
called hunks.
<p>
The
<i>patch</i>
utility recognises the following expression in the
header information:
<dl compact>

<dt><b>Index:&nbsp;</b><i>pathname</i><dd>
The file to be patched is named
<i>pathname</i>.

</dl>
<p>
If all lines (including headers) within a patch begin with the
same leading sequence of
blank characters,
the
<i>patch</i>
utility will remove this sequence before proceeding.
Within each patch, if the type of difference is context, the
<i>patch</i>
utility recognises the following expressions:
<dl compact>

<dt><b>***&nbsp;</b><i>filename&nbsp;timestamp</i><dd>
The patches arose from
<i>filename.</i>

<dt><b>---&nbsp;</b><i>filename&nbsp;timestamp</i><dd>
The patches should be applied to
<i>filename.</i>

</dl>
<p>
Each hunk within a patch must be the
<i><a href="diff.html">diff</a></i>
output to change a line
range within the original file.
The line numbers for successive
hunks within a patch must occur in ascending order.
<h5><a name = "tag_001_014_1662_002">&nbsp;</a>Filename Determination</h5>
<xref type="5" name="patchfd"></xref>
If no
<i>file</i>
operand is specified,
<i>patch</i>
performs the following steps to obtain a pathname:
<ol>
<p>
<li>
If the patch contains the strings
***
and
---,
the
<i>patch</i>
utility strips components from the beginning of each
pathname (depending on the presence or value of the
<b>-p</b>
option), then tests for the
existence of both files in the current directory (or
directory specified with the
<b>-d</b>
option).
If both files exist,
<i>patch</i>
assumes that no pathname can be obtained from this step.
<p>
<li>
If the header information contains a line with the string
<b>Index:</b>,
<i>patch</i>
utility strips components from the
beginning of the pathname (depending on
<b>-p</b>),
then tests for the existence of this file in the current directory
(or directory specified with the
<b>-d</b>
option).
<p>
<li>
If an
<b>SCCS</b>
directory exists in the current directory,
<i>patch</i>
will attempt to perform a
<i><a href="get.html">get</a></i>
<b>-e</b>
SCCS/s.<i>filename</i>
command to retrieve an editable version of the file.
<p>
<li>
If no pathname can be obtained by applying the previous steps,
or if the pathnames obtained do not exist,
<i>patch</i>
will write a prompt to standard output and
request a filename interactively from standard input.
<p>
</ol>
<h5><a name = "tag_001_014_1662_003">&nbsp;</a>Patch Application</h5>
<xref type="5" name="patchapp"></xref>
If the
<b>-c</b>,
<b>-e</b>
or
<b>-n</b>
option is present, the
<i>patch</i>
utility will
interpret information within each hunk as a context difference, an
<i><a href="ed.html">ed</a></i>
difference or a normal difference, respectively.
In the absence of any of
these options, the
<i>patch</i>
utility determines the type of difference
based on the format of information within the hunk.
<p>
For each hunk, the
<i>patch</i>
utility begins to search for the
place to apply the patch at the line number at the beginning of
the hunk, plus or minus any offset used in applying the previous hunk.
If lines matching the hunk context are
not found,
<i>patch</i>
scans both forwards and backwards at least
1000 bytes for a set of lines that match the hunk context.
<p>
If no such place is found and it is a context difference, then another
scan will take place, ignoring the first and last line of context.
If that fails, the first two and last two lines of context will be ignored
and another scan will be made.
Implementations may search more extensively for installation locations.
<p>
If no location can be found, the
<i>patch</i>
utility will append the
hunk to the reject file.
The rejected hunk will be written in
context-difference format regardless of the format of the patch file.
If the input was a normal or
<i><a href="ed.html">ed</a></i>-style
difference, the reject file may contain differences
with zero lines of context.
The line numbers on the hunks in the
reject file may be different from the line numbers in the patch
file since they will reflect the approximate locations for the
failed hunks in the new file rather than the old one.
<p>
If the type of patch is an
<i><a href="ed.html">ed</a></i>
diff,
the implementation may accomplish the patching by invoking the
<i><a href="ed.html">ed</a></i>
utility.
</blockquote><h4><a name = "tag_001_014_1663">&nbsp;</a>EXIT STATUS</h4><blockquote>
The following exit values are returned:
<dl compact>

<dt>0<dd>Successful completion.

<dt>1<dd>One or more lines were written to a reject file.

<dt>&gt;1<dd>An error occurred.

</dl>
</blockquote><h4><a name = "tag_001_014_1664">&nbsp;</a>CONSEQUENCES OF ERRORS</h4><blockquote>
Patches that cannot be correctly placed in the file
will be written to a reject file.
<br>
</blockquote><h4><a name = "tag_001_014_1665">&nbsp;</a>APPLICATION USAGE</h4><blockquote>
The
<b>-R</b>
option will not work with
<i><a href="ed.html">ed</a></i>
scripts because there is too little information to reconstruct
the reverse operation.
<p>
The
<b>-p</b>
option makes it possible to customise a patchfile to local
user directory structures without manually editing the patchfile.
For example, if the filename in the patch file was:
<pre>
<code>
/curds/whey/src/blurfl/blurfl.c
</code>
</pre>
<p>
Setting
<b>-p 0</b>
gives the entire pathname unmodified;
<b>-p 1</b>
gives:
<pre>
<code>
curds/whey/src/blurfl/blurfl.c
</code>
</pre>
<p>
without the leading slash,
<b>-p 4</b>
gives:
<pre>
<code>
blurfl/blurfl.c
</code>
</pre>
<p>
and not specifying
<b>-p</b>
at all gives:
<pre>
<code>
blurfl.c .
</code>
</pre>
<p>
When using
<b>-b</b>
in some file system implementations, the saving of a
<b>.orig</b>
file may produce unwanted results.
In the case of 12, 13 or 14-character filenames,
on file systems supporting 14-character maximum filenames, the
<b>.orig</b>
file will overwrite the new file.
</blockquote><h4><a name = "tag_001_014_1666">&nbsp;</a>EXAMPLES</h4><blockquote>
None.
</blockquote><h4><a name = "tag_001_014_1667">&nbsp;</a>FUTURE DIRECTIONS</h4><blockquote>
The IEEE PASC 1003.2 Interpretations Committee has forwarded concerns about
parts of this interface definition to the IEEE PASC Shell and Utilities Working Group
which is identifying the corrections.
A future revision of this specification will align with
IEEE Std. 1003.2b when finalised.
</blockquote><h4><a name = "tag_001_014_1668">&nbsp;</a>SEE ALSO</h4><blockquote>
<i><a href="ed.html">ed</a></i>,
<i><a href="diff.html">diff</a></i>.
</blockquote><hr size=2 noshade>
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