patch

- apply changes to files

Synopsis

patch [-blNR] [-c | -e | -n | -u] [-d dir] [-D define] 
     [-i patchfile] [-o outfile] [-p num] [-r rejectfile] 
     [file]

Description

The patch command reads a source (patch) file containing any of the three forms of difference (diff) listings produced by the diff(1) command (normal, context or in the style of ed(1)) and apply those differences to a file. By default, patch reads from the standard input.

patch attempts to determine the type of the diff listing, unless overruled by a -c, -e, or -n option.

If the patch file contains more than one patch, patch attempts to apply each of them as if they came from separate patch files. (In this case the name of the patch file must be determinable for each diff listing.)

Options

The following options are supported:

-b

Saves 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 is overwritten. If multiple patches are applied to the same file, the .orig file is written only for the first patch. When the -o outfile option is also specified, file.orig is not created but, if outfile already exists, outfile.orig is created.

-c

Interprets the patch file as a context difference (the output of the command diff when the -c or -C options are specified).

-d dir

Changes the current directory to dir before processing as described in EXTENDED DESCRIPTION.

-D define

Marks changes with the C preprocessor construct:

#ifdef define
. . .
#endif

The option-argument define is used as the differentiating symbol.

-e

Interprets the patch file as an ed script, rather than a diff script.

-i patchfile

Reads the patch information from the file named by the path name patchfile, rather than the standard input.

-l

(The letter ell.) Causes any sequence of blank characters in the difference script to match any sequence of blank characters in the input file. Other characters is matched exactly.

-n

Interprets the script as a normal difference.

-N

Ignores patches where the differences have already been applied to the file; by default, already-applied patches are rejected.

-o outfile

Instead of modifying the files (specified by the file operand or the difference listings) directly, writes a copy of the file referenced by each patch, with the appropriate differences applied, to outfile. Multiple patches for a single file is applied to the intermediate versions of the file created by any previous patches, and results in multiple, concatenated versions of the file being written to outfile.

-p num

For all path names in the patch file that indicate the names of files to be patched, deletes num path name components from the beginning of each path name. If the path name in the patch file is absolute, any leading slashes are considered the first component (that is, -p 1 removes the leading slashes). Specifying -p 0 causes the full path name to be used. If -p is not specified, only the basename (the final path name component) is used.

-R

Reverses the sense of the patch script. That is, assumes that the difference script was created from the new version to the old version. The -R option cannot be used with ed scripts. patch attempts to reverse each portion of the script before applying it. Rejected differences is 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 is prompted to determine if the -R option should be set.

-r rejectfile

Overrides the default reject file name. In the default case, the reject file has the same name as the output file, with the suffix .rej appended to it. See Patch Application.

-u

Interprets the patch file as a unified context difference, that is, the output of the command diff when the -u or -U options are specified.

Operands

The following operand is supported:

file

A path name of a file to patch.

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 example, if the file name in the patch file was /curds/whey/src/blurfl/blurfl.c:

• Setting -p 0 gives the entire path name unmodified.

• Setting -p 1 gives:

  curds/whey/src/blurfl/blurfl.c

• Without the leading slash, -p 4 gives:

  blurfl/blurfl.c

• Not specifying -p at all gives:

  blurfl.c

When using -b in some file system implementations, the saving of a .orig file might produce unwanted results. In the case of 12–, 13–, or 14-character file names, on file systems supporting 14-character maximum file names, the .orig file overwrites the new file.

Environment Variables

See environ(5) for descriptions of the following environment variables that affect the execution of patch: LANG, LC_ALL, LC_COLLATE, LC_CTYPE, LC_MESSAGES, LC_TIME, and NLSPATH.

Affirmative responses are processed using the extended regular expression defined for the yesexpr keyword in the LC_MESSAGES category of the user's locale. The locale specified in the LC_COLLATE category defines the behavior of ranges, equivalence classes, and multi-character collating elements used in the expression defined for yesexpr. The locale specified in LC_CTYPE determines the locale for interpretation of sequences of bytes of text data a characters, the behavior of character classes used in the expression defined for the yesexpr. See locale(5).

OUTPUT FILES

The output of patch the save files (.orig suffixes) and the reject files (.rej suffixes) are text files.

Extended Description

A patch file can contain patching instructions for more than one file. File names are determined as specified in Patch Determination. When the -b option is specified, for each patched file, the original is saved in a file of the same name with the suffix .orig appended to it.

For each patched file, a reject file can also be created as noted in Patch Application. In the absence of an -r option, the name of this file is formed by appending the suffix .rej to the original file name.

Patch File Format

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 file name identification in the format produced by diff -c, and one or more sets of diff output, which are customarily called hunks.

patch recognizes 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 characters, patch removes this sequence before proceeding. Within each patch, if the type of difference is context, patch recognizes the following expressions:

* * * filename timestamp

The patches arose from filename.

- - - filename timestamp

The patches should be applied to filename.

Each hunk within a patch must be the diff output to change a line range within the original file. The line numbers for successive hunks within a patch must occur in ascending order.

File Name Determination

If no file operand is specified, patch performs the following steps to obtain a path name:

1. If the patch contains the strings *** and - - -, patch strips components from the beginning of each path name (depending on the presence or value of the -p option), then tests for the existence of both files in the current directory (or directory specified with the -d option).

2. If both files exist, patch assumes that no path name can be obtained from this step. If the header information contains a line with the string Index:, patch strips components from the beginning of the path name (depending on -p), then tests for the existence of this file in the current directory (or directory specified with the -d option).

3. If an SCCS directory exists in the current directory, patch attempts to perform a get -e SCCS/s.filename command to retrieve an editable version of the file.

4. If no path name can be obtained by applying the previous steps, or if the path names obtained do not exist, patch writes a prompt to standard output and request a file name interactively from standard input.

Patch Application

If the -c, -e, -n, or -u option is present, patch interprets information within each hunk as a context difference, an ed difference, a normal difference, or a unified context difference, respectively. In the absence of any of these options, patch determines the type of difference based on the format of information within the hunk.

For each hunk, patch 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, patch scans 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 takes place, ignoring the first and last line of context. If that fails, the first two and last two lines of context is ignored and another scan is made. Implementations can search more extensively for installation locations.

If no location can be found, patch appends the hunk to the reject file. The rejected hunk is written in context-difference format regardless of the format of the patch file. If the input was a normal or ed -style difference, the reject file can contain differences with zero lines of context. The line numbers on the hunks in the reject file can be different from the line numbers in the patch file since they 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 can accomplish the patching by invoking the ed command.

Exit Status

The following exit values are returned:

0

Successful completion.

1

One or more lines were written to a reject file.

>1

An error occurred.

Attributes

See attributes(5) for descriptions of the following attributes:

See Also

ed(1), diff(1), attributes(5), environ(5), standards(5)