применить файл сравнения к оригиналу (apply a diff file to an original)
Описание (Description)
patch takes a patch file patchfile containing a difference
listing produced by the diff program and applies those
differences to one or more original files, producing patched
versions. Normally the patched versions are put in place of the
originals. Backups can be made; see the -b or --backup option.
The names of the files to be patched are usually taken from the
patch file, but if there's just one file to be patched it can be
specified on the command line as originalfile.
Upon startup, patch attempts to determine the type of the diff
listing, unless overruled by a -c (--context), -e (--ed), -n
(--normal), or -u (--unified) option. Context diffs (old-style,
new-style, and unified) and normal diffs are applied by the patch
program itself, while ed diffs are simply fed to the ed(1) editor
via a pipe.
patch tries 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, if lines
end in CRLF, or if a diff is encapsulated one or more times by
prepending "- " to lines starting with "-" as specified by
Internet RFC 934, this is taken into account. After removing
indenting or encapsulation, lines beginning with # are ignored,
as they are considered to be comments.
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 attempts 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 scans
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.)
Hunks with less prefix context than suffix context (after
applying fuzz) must apply at the start of the file if their first
line number is 1. Hunks with more prefix context than suffix
context (after applying fuzz) must apply at the end of the file.
If patch cannot find a place to install that hunk of the patch,
it puts the hunk out to a reject file, which normally is the name
of the output file plus a .rej suffix, or # if .rej would
generate a file name that is too long (if even appending the
single character # makes the file name too long, then # replaces
the file name's last character).
The rejected hunk comes out in unified or context diff format.
If the input was a normal diff, many of the contexts are simply
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 are told if the hunk failed, and
if so which line (in the new file) patch thought the hunk should
go on. If the hunk is installed at a different line from the
line number specified in the diff, you are told the offset. A
single large offset may indicate that a hunk was installed in the
wrong place. You are also told if a fuzz factor was used to make
the match, in which case you should also be slightly suspicious.
If the --verbose option is given, you are also told about hunks
that match exactly.
If no original file origfile is specified on the command line,
patch tries to figure out from the leading garbage what the name
of the file to edit is, using the following rules.
First, patch takes an ordered list of candidate file names as
follows:
• If the header is that of a context diff, patch takes the old
and new file names in the header. A name is ignored if it
does not have enough slashes to satisfy the -pnum or
--strip=num option. The name /dev/null is also ignored.
• If there is an Index: line in the leading garbage and if
either the old and new names are both absent or if patch is
conforming to POSIX, patch takes the name in the Index: line.
• For the purpose of the following rules, the candidate file
names are considered to be in the order (old, new, index),
regardless of the order that they appear in the header.
Then patch selects a file name from the candidate list as
follows:
• If some of the named files exist, patch selects the first name
if conforming to POSIX, and the best name otherwise.
• If patch is not ignoring RCS, ClearCase, Perforce, and SCCS
(see the -g num or --get=num option), and no named files exist
but an RCS, ClearCase, Perforce, or SCCS master is found,
patch selects the first named file with an RCS, ClearCase,
Perforce, or SCCS master.
• If no named files exist, no RCS, ClearCase, Perforce, or SCCS
master was found, some names are given, patch is not
conforming to POSIX, and the patch appears to create a file,
patch selects the best name requiring the creation of the
fewest directories.
• If no file name results from the above heuristics, you are
asked for the name of the file to patch, and patch selects
that name.
To determine the best of a nonempty list of file names, patch
first takes all the names with the fewest path name components;
of those, it then takes all the names with the shortest basename;
of those, it then takes all the shortest names; finally, it takes
the first remaining name.
Additionally, if the leading garbage contains a Prereq: line,
patch takes the first word from the prerequisites line (normally
a version number) and checks the original file to see if that
word can be found. If not, patch asks for confirmation before
proceeding.
The upshot of all this is that you should be able to say, while
in a news interface, something like 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 patch file contains more than one patch, patch tries 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 contains
interesting things such as file names and revision level, as
mentioned previously.
