PATCH(P) POSIX Programmer's Manual PATCH(P)NAMEpatch - apply changes to files
SYNOPSISpatch [-blNR][ -c| -e| -n][-d dir][-D define][-i patchfile]
[-o outfile][-p num][-r rejectfile][file]
DESCRIPTION
The patch utility shall read a source (patch) file containing any of
the three forms of difference (diff) listings produced by the diff
utility (normal, context, or in the style of ed) and apply those dif‐
ferences to a file. By default, patch shall read from the standard
input.
The patch utility shall attempt to determine the type of the diff list‐
ing, unless overruled by a -c, -e, or -n option.
If the patch file contains more than one patch, patch shall attempt to
apply each of them as if they came from separate patch files. (In this
case, the application shall ensure that the name of the patch file is
determinable for each diff listing.)
OPTIONS
The patch utility shall conform to the Base Definitions volume of
IEEE Std 1003.1-2001, Section 12.2, Utility Syntax Guidelines.
The following options shall be supported:
-b Save a copy of the original contents of each modified file,
before the differences are applied, in a file of the same name
with the suffix .orig appended to it. If the file already
exists, it shall be overwritten; if multiple patches are applied
to the same file, the .orig file shall be written only for the
first patch. When the -o outfile option is also specified, file
.orig shall not be created but, if outfile already exists, out‐
file .orig shall be created.
-c Interpret the patch file as a context difference (the output of
the utility diff when the -c or -C options are specified).
-d dir
Change the current directory to dir before processing as
described in the EXTENDED DESCRIPTION section.
-D define
Mark changes with one of the following C preprocessor con‐
structs:
#ifdef define
...
#endif
#ifndef define
...
#endif
optionally combined with the C preprocessor construct #else. If the
patched file is processed with the C preprocessor, where the macro
define is defined, the output shall contain the changes from the patch
file; otherwise, the output shall not contain the patches specified in
the patch file.
-e Interpret the patch file as an ed script, rather than a diff
script.
-i patchfile
Read the patch information from the file named by the pathname
patchfile, rather than the standard input.
-l (The letter ell.) Cause any sequence of <blank>s in the differ‐
ence script to match any sequence of <blank>s in the input file.
Other characters shall be matched exactly.
-n Interpret the script as a normal difference.
-N Ignore patches where the differences have already been applied
to the file; by default, already-applied patches shall be
rejected.
-o outfile
Instead of modifying the files (specified by the file operand or
the difference listings) directly, write a copy of the file ref‐
erenced by each patch, with the appropriate differences applied,
to outfile. Multiple patches for a single file shall be applied
to the intermediate versions of the file created by any previous
patches, and shall result in multiple, concatenated versions of
the file being written to outfile.
-p num
For all pathnames in the patch file that indicate the names of
files to be patched, delete num pathname components from the
beginning of each pathname. If the pathname in the patch file is
absolute, any leading slashes shall be considered the first com‐
ponent (that is, -p 1 shall remove the leading slashes). Speci‐
fying -p 0 shall cause the full pathname to be used. If -p is
not specified, only the basename (the final pathname component)
shall be used.
-R Reverse the sense of the patch script; that is, assume that the
difference script was created from the new version to the old
version. The -R option cannot be used with ed scripts. The
patch utility shall attempt to reverse each portion of the
script before applying it. Rejected differences shall be saved
in swapped format. If this option is not specified, and until a
portion of the patch file is successfully applied, patch
attempts to apply each portion in its reversed sense as well as
in its normal sense. If the attempt is successful, the user
shall be prompted to determine whether the -R option should be
set.
-r rejectfile
Override the default reject filename. In the default case, the
reject file shall have the same name as the output file, with
the suffix .rej appended to it; see Patch Application .
OPERANDS
The following operand shall be supported:
file A pathname of a file to patch.
STDIN
See the INPUT FILES section.
INPUT FILES
Input files shall be text files.
ENVIRONMENT VARIABLES
The following environment variables shall affect the execution of
patch:
LANG Provide a default value for the internationalization variables
that are unset or null. (See the Base Definitions volume of
IEEE Std 1003.1-2001, Section 8.2, Internationalization Vari‐
ables for the precedence of internationalization variables used
to determine the values of locale categories.)
LC_ALL If set to a non-empty string value, override the values of all
the other internationalization variables.
LC_CTYPE
Determine the locale for the interpretation of sequences of
bytes of text data as characters (for example, single-byte as
opposed to multi-byte characters in arguments and input files).
LC_MESSAGES
Determine the locale that should be used to affect the format
and contents of diagnostic messages written to standard error
and informative messages written to standard output.
NLSPATH
Determine the location of message catalogs for the processing of
LC_MESSAGES .
LC_TIME
Determine the locale for recognizing the format of file time‐
stamps written by the diff utility in a context-difference input
file.
ASYNCHRONOUS EVENTS
Default.
STDOUT
Not used.
STDERR
The standard error shall be used for diagnostic and informational mes‐
sages.
OUTPUT FILES
The output of the patch utility, the save files ( .orig suffixes), and
the reject files ( .rej suffixes) shall be text files.
EXTENDED DESCRIPTION
A patch file may contain patching instructions for more than one file;
filenames shall be determined as specified in Filename Determination .
When the -b option is specified, for each patched file, the original
shall be saved in a file of the same name with the suffix .orig
appended to it.
For each patched file, a reject file may also be created as noted in
Patch Application . In the absence of a -r option, the name of this
file shall be formed by appending the suffix .rej to the original file‐
name.
Patch File Format
The patch file shall contain zero or more lines of header information
followed by one or more patches. Each patch shall contain zero or more
lines of filename identification in the format produced by diff -c, and
one or more sets of diff output, which are customarily called hunks.
The patch utility shall recognize the following expression in the
header information:
Index: pathname
The file to be patched is named pathname.
If all lines (including headers) within a patch begin with the same
leading sequence of <blank>s, the patch utility shall remove this
sequence before proceeding. Within each patch, if the type of differ‐
ence is context, the patch utility shall recognize the following
expressions:
*** filename timestamp
The patches arose from filename.
--- filename timestamp
The patches should be applied to filename.
Each hunk within a patch shall be the diff output to change a line
range within the original file. The line numbers for successive hunks
within a patch shall occur in ascending order.
Filename Determination
If no file operand is specified, patch shall perform the following
steps to determine the filename to use:
1. If the type of diff is context, the patch utility shall delete
pathname components (as specified by the -p option) from the file‐
name on the line beginning with "***" , then test for the existence
of this file relative to the current directory (or the directory
specified with the -d option). If the file exists, the patch util‐
ity shall use this filename.
2. If the type of diff is context, the patch utility shall delete the
pathname components (as specified by the -p option) from the file‐
name on the line beginning with "---" , then test for the existence
of this file relative to the current directory (or the directory
specified with the -d option). If the file exists, the patch util‐
ity shall use this filename.
3. If the header information contains a line beginning with the string
Index:, the patch utility shall delete pathname components (as
specified by the -p option) from this line, then test for the exis‐
tence of this file relative to the current directory (or the direc‐
tory specified with the -d option). If the file exists, the patch
utility shall use this filename.
4. If an SCCS directory exists in the current directory, patch shall
attempt to perform a get -e SCCS/s. filename command to retrieve an
editable version of the file. If the file exists, the patch utility
shall use this filename.
5. The patch utility shall write a prompt to standard output and
request a filename interactively from the controlling terminal (for
example, /dev/tty).
Patch Application
If the -c, -e, or -n option is present, the patch utility shall inter‐
pret information within each hunk as a context difference, an ed dif‐
ference, or a normal difference, respectively. In the absence of any of
these options, the patch utility shall determine the type of difference
based on the format of information within the hunk.
For each hunk, the patch utility shall begin 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 match‐
ing the hunk context are not found, patch shall scan both forwards and
backwards at least 1000 bytes for a set of lines that match the hunk
context.
If no such place is found and it is a context difference, then another
scan shall take place, ignoring the first and last line of context. If
that fails, the first two and last two lines of context shall be
ignored and another scan shall be made. Implementations may search
more extensively for installation locations.
If no location can be found, the patch utility shall append the hunk to
the reject file. The rejected hunk shall be written in context-differ‐
ence format regardless of the format of the patch file. If the input
was a normal or ed-style difference, the reject file may contain dif‐
ferences 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 shall reflect the approximate locations for the failed
hunks in the new file rather than the old one.
If the type of patch is an ed diff, the implementation may accomplish
the patching by invoking the ed utility.
EXIT STATUS
The following exit values shall be returned:
0 Successful completion.
1 One or more lines were written to a reject file.
>1 An error occurred.
CONSEQUENCES OF ERRORS
Patches that cannot be correctly placed in the file shall be written to
a reject file.
The following sections are informative.
APPLICATION USAGE
The -R option does not work with ed scripts because there is too little
information to reconstruct the reverse operation.
The -p option makes it possible to customize a patch file to local user
directory structures without manually editing the patch file. For exam‐
ple, if the filename in the patch file was:
/curds/whey/src/blurfl/blurfl.c
Setting -p 0 gives the entire pathname unmodified; -p 1 gives:
curds/whey/src/blurfl/blurfl.c
without the leading slash, -p 4 gives:
blurfl/blurfl.c
and not specifying -p at all gives:
blurfl.c .
EXAMPLES
None.
RATIONALE
Some of the functionality in historical patch implementations was not
specified. The following documents those features present in historical
implementations that have not been specified.
A deleted piece of functionality was the '+' pseudo-option allowing an
additional set of options and a patch file operand to be given. This
was seen as being insufficiently useful to standardize.
In historical implementations, if the string "Prereq:" appeared in the
header, the patch utility would search for the corresponding version
information (the string specified in the header, delimited by <blank>s
or the beginning or end of a line or the file) anywhere in the original
file. This was deleted as too simplistic and insufficiently trustworthy
a mechanism to standardize. For example, if:
Prereq: 1.2
were in the header, the presence of a delimited 1.2 anywhere in the
file would satisfy the prerequisite.
The following options were dropped from historical implementations of
patch as insufficiently useful to standardize:
-b The -b option historically provided a method for changing the
name extension of the backup file from the default .orig. This
option has been modified and retained in this volume of
IEEE Std 1003.1-2001.
-F The -F option specified the number of lines of a context diff to
ignore when searching for a place to install a patch.
-f The -f option historically caused patch not to request addi‐
tional information from the user.
-r The -r option historically provided a method of overriding the
extension of the reject file from the default .rej.
-s The -s option historically caused patch to work silently unless
an error occurred.
-x The -x option historically set internal debugging flags.
In some file system implementations, the saving of a .orig file may
produce unwanted results. In the case of 12, 13, or 14-character file‐
names (on file systems supporting 14-character maximum filenames), the
.orig file overwrites the new file. The reject file may also exceed
this filename limit. It was suggested, due to some historical practice,
that a tilde ( '~' ) suffix be used instead of .orig and some other
character instead of the .rej suffix. This was rejected because it is
not obvious to the user which file is which. The suffixes .orig and
.rej are clearer and more understandable.
The -b option has the opposite sense in some historical implementa‐
tions-do not save the .orig file. The default case here is not to save
the files, making patch behave more consistently with the other stan‐
dard utilities.
The -w option in early proposals was changed to -l to match historical
practice.
The -N option was included because without it, a non-interactive appli‐
cation cannot reject previously applied patches. For example, if a
user is piping the output of diff into the patch utility, and the user
only wants to patch a file to a newer version non-interactively, the -N
option is required.
Changes to the -l option description were proposed to allow matching
across <newline>s in addition to just <blank>s. Since this is not his‐
torical practice, and since some ambiguities could result, it is sug‐
gested that future developments in this area utilize another option
letter, such as -L.
FUTURE DIRECTIONS
None.
SEE ALSO
ed , diff
COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
Electrical and Electronics Engineers, Inc and The Open Group. In the
event of any discrepancy between this version and the original IEEE and
The Open Group Standard, the original IEEE and The Open Group Standard
is the referee document. The original Standard can be obtained online
at http://www.opengroup.org/unix/online.html .
IEEE/The Open Group 2003 PATCH(P)
