HP-UX Reference (11i v1 05/09) - 1 User Commands N-Z (vol 2)

p
patch(1) patch(1)
NAME
patch - a program for applying a diff file to an original
SYNOPSIS
Non-XPG4 version
patch [options] orig patchfile [
+[ options] orig]
patch <patchfile # usual form
XPG4 version
patch [-blNR][-c|-e|-n
][-d dir][-D define][
-i patchfile][-o outfile][-p
num]
[
-r rejectfile][file]
DESCRIPTION
patch will take a patch file containing any of the three forms of difference listing produced by the diff pro-
gram (normal, context or in the style of ed) 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 ‘‘.orig’’, or as specified by the
-b switch. Note that functionality
of this option varies for XPG4 version. You may also specify where you want the output to go with a
-o
switch. If patchfile is omitted, or is a hyphen, the patch will be read from standard input. For XPG4 ver-
sion, patchfile has to be specified as argument to -i switch. If this option is omitted or a hyphen is specified
as argument, the patch will read from standard input.
Upon startup, patch will attempt to determine the type of the diff listing, unless over-ruled by a
-c, -e,or
-n switch. Context diffs and normal diffs are applied by the patch program itself, while ed diffs are simply
fed to the ed editor via a pipe.
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 patch, and it should work. If the entire diff is
indented by a consistent amount, this will be taken into account.
With context diffs, and to a lesser extent with normal diffs, patch can detect when the line numbers men-
tioned 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, patch will scan both forwards and backwards for a set of
lines matching the context given in the hunk. First 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.) Note that for XPG4 version maximum fuzz factor can not
be specified as an option and the default maximum fuzz factor is used. If 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 ‘‘.rej’’. (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.
As each hunk is completed, you will be told whether the hunk succeeded or failed, and which line (in the
new file) 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. Note that XPG4 version does not support verbose option. So, most of the diag-
nostic messages are not printed for this version. However user queries will always be displayed.
If no original file is specified on the command line, 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 begin-
ning with ‘‘***’’ or ‘‘---’’, with the shortest name of an existing file winning. Only context diffs have lines
like that, but if there is an ‘‘Index:’’ line in the leading garbage, 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.
(If the original file cannot be found, but a suitable SCCS or RCS file is handy, patch will attempt to get or
check out the file.)
Additionally, if the leading garbage contains a ‘‘Prereq: ’’ line, 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
Section 1−−692 Hewlett-Packard Company − 1 − HP-UX 11i Version 1: September 2005