patch is as specified in the Single UNIX Specification but with differences as listed below.
reads and write all files in binary mode, except for standard output and /dev/tty. This option has no effect on POSIX-compliant systems.
interprets the patch file as a unified context diff.
The behaviors specified in this section are expected to disappear from a future version of the LSB; applications should only use the non-LSB-deprecated behaviors.
backs up a file if the patch does not match the file exactly and if backups are not otherwise requested.
does not back up a file if the patch does not match the file exactly and if backups are not otherwise requested.
prefixes pref to a file name when generating its simple backup file name.
prints the results of applying the patches without actually changing any files.
removes output files that are empty after the patches have been applied. When patch removes a file, it also attempts to remove any empty ancestor directories.
skips patches whose headers do not say which file is to be patched; patches files even though they have the wrong version for the Prereq: line in the patch; assumes that patches are not reversed even if they look like they are.
sets the maximum fuzz factor. This option only applies to diffs that have context, and ignores up to that many lines in looking for places to install a hunk.
controls patch behavior when a file is under RCS or SCCS control and does not exist or is read-only and matches the default version. If num is positive, patch gets (or checks out) the file from the revision control system; if zero, patch ignores RCS and SCCS and does not get the file; and if negative, patch asks the user where to get the file.
works silently, unless an error occurs.
suppresses questions like -f, but makes some different assumptions: skips patches whose headers do not contain file names; skips patches for which the file has the wrong version for the Prereq: line in the patch; and assumes that patches are reversed if they look like they are.
sets the modification and access times of patched files from time stamps given in context diff headers, assuming that the context diff headers use local time.
prints out patch's revision header and patch level, and exits.
uses method to determine backup file names. The method can also be given by the PATCH_VERSION_CONTROL environment variable, which is overridden by this option.
outputs extra information about the work being done.
prefixes pref to the basename of a file name when generating its simple backup file name.
uses suffix as the simple backup suffix.
sets the modification and access times of patched files from time stamps given in context diff headers.
displays this help and exits.