patch
Normally patch is invoked like this:
patch <patchfile
The full format for invoking patch is:
patch options... [origfile [patchfile]] [+ options... [origfile]]...
If you do not specify patchfile, or if patchfile is
`-', patch reads the patch (that is, the diff output)
from the standard input.
You can specify one or more of the original files as orig arguments; each one and options for interpreting it is separated from the others with a `+'. See section Multiple Patches in a File, for more information.
If you do not specify an input file on the command line, patch
tries to figure out from the leading text (any text in the patch
that comes before the diff output) which file to edit. In the
header of a context or unified diff, patch looks in lines
beginning with `***', `---', or `+++'; among those, it
chooses the shortest name of an existing file. Otherwise, if there is
an `Index:' line in the leading text, patch tries to use the
file name from that line. If patch cannot figure out the name of
an existing file from the leading text, it prompts you for the name of
the file to patch.
If the input file does not exist or is read-only, and a suitable RCS or
SCCS file exists, patch attempts to check out or get the file
before proceeding.
By default, patch replaces the original input file with the
patched version, after renaming the original file into a backup file
(see section Backup File Names, for a description of how patch names backup
files). You can also specify where to put the output with the `-o
output-file' or `--output=output-file' option.
patch.