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will attempt to determine the type of the diff listing, unless overruled by a
If the patchfile contains more than one patch, 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 file names and revision level (see the section on Filename Determination below).
The options are as follows:
Save a backup copy of the file before it is modified.
By default the original file is saved with a backup extension of
unless the file already has a numbered backup, in which case a numbered
backup is made.
This is equivalent to specifying
|Checks that the patch would apply cleanly, but does not modify anything.|
|Forces patch to interpret the patch file as a context diff.|
|Causes patch to remove output files that are empty after the patches have been applied. This option is useful when applying patches that create or remove files.|
|Forces patch to interpret the patch file as an ed(1) script.|
to assume that the user knows exactly what he or she is doing, and to not
ask any questions.
It assumes the following:
skip patches for which a file to patch cannot be found;
patch files even though they have the wrong version for the
line in the patch;
and assume that patches are not reversed even if they look like they are.
This option does not suppress commentary; use
|Causes the pattern matching to be done loosely, in case the tabs and spaces have been munged in your input file. Any sequence of whitespace in the pattern line will match any sequence in the input file. Normal characters must still match exactly. Each line of the context must still match a line in the input file.|
to ignore patches that it thinks are reversed or already applied.
|Forces patch to interpret the patch file as a normal diff.|
without the leading slash.
that this patch was created with the old and new files swapped.
(Yes, I am afraid that does happen occasionally, human nature being what it
will attempt to swap each hunk around before applying it.
Rejects will come out in the swapped format.
If the first hunk of a patch fails,
will reverse the hunk to see if it can be applied that way.
If it can, you will be asked if you want to have the
|Forces patch to interpret the patch file as a unified context diff (a unidiff).|
|Always make numbered backups.|
|Make numbered backups of files that already have them, simple backups of the others.|
|Always make simple backups.|
|none||Do not make backups.|
|Causes patch to print out its revision header and patch level.|
IEEE Std 1003.1-2008 ("POSIX.1")
With context diffs, and to a lesser extent with normal diffs, 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, 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 is 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 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.
If the diff is a context or unified diff, patch is able to determine the old and new file names from the diff header. For context diffs, the "old" file is specified in the line beginning with "***" and the "new" file is specified in the line beginning with "---". For a unified diff, the "old" file is specified in the line beginning with "---" and the "new" file is specified in the line beginning with "+++". If there is an "Index:" line in the leading garbage (regardless of the diff type), patch will use the file name from that line as the "index" file.
patch will choose the file name by performing the following steps, with the first match used:
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 not, patch will ask for confirmation before proceeding.
The upshot of all this is that you should be able to say, while in a news interface, the following:
| patch -d /usr/src/local/blurfl
and patch a file in the blurfl directory directly from the article containing the patch.
If the backup file is a symbolic or hard link to the original file, 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 or is not linked to the original file.
You may also specify where you want the output to go with the
First, you can save people a lot of grief by keeping a patchlevel.h file which is patched to increment the patch level as the first diff in the patch file you send out. If you put a "Prereq:" line in with the patch, it will not let them apply patches out of order without some warning.
Second, make sure you have specified the file names right, either in a
context diff header, or with an
If you are patching something in a subdirectory, be sure to tell the patch
user to specify a
Third, you can create a file by sending out a diff that compares a null file to the file you want to create. This will only work if the file you want to create does not exist already in the target directory.
Fourth, take care not to send out reversed patches, since it makes people wonder whether they already applied the patch.
Fifth, while you may be able to get away with putting 582 diff listings into one file, it is probably wiser to group related patches into separate files in case something goes haywire.
behaves as if the
|SIMPLE_BACKUP_SUFFIX||Extension to use for backup file names instead of ".orig".|
|TMPDIR||Directory to put temporary files in; default is /tmp.|
|Selects when numbered backup files are made.|
|VERSION_CONTROL||Same as PATCH_VERSION_CONTROL.|
|patch temporary files|
|/dev/tty||used to read input when patch prompts the user|
|1||One or more lines were written to a reject file.|
|>1||An error occurred.|
When applying a set of patches in a loop it behooves you to check this exit status so you do not apply a later patch to a partially patched file.
The message "Hmm..." indicates that there is unprocessed text in the patch file and that patch is attempting to intuit whether there is a patch in that text and, if so, what kind of patch it is.
patch usually produces the correct results, even when it has to do a lot of guessing. However, the results are guaranteed to be correct only when the patch is applied to exactly the same version of the file that the patch was generated from.
Check patch mode
If code has been duplicated (for instance with #ifdef OLDCODE ... #else ... #endif), patch is incapable of patching both versions, and, if it works at all, will likely patch the wrong one, and tell you that it succeeded to boot.
If you apply a patch you have already applied, patch will think it is a reversed patch, and offer to un-apply the patch. This could be construed as a feature.
|PATCH (1)||August 15, 2015|
|Main index||Section 1||日本語||한국인||Options|
|“||If you have a problem and you think awk(1) is the solution, then you have two problems.||”|
|— David Tilbrook|