patch and the POSIX Standard
If you specify the --posix option, or set the
POSIXLY_CORRECT environment variable,
more strictly to the POSIX standard, as follows:
- Take the first existing file from the list (old, new, index)
when intuiting file names from diff headers. See Multiple Patches.
- Do not remove files that are removed by a diff.
See Creating and Removing.
- Do not ask whether to get files from RCS, ClearCase, or
SCCS. See Revision Control.
- Require that all options precede the files in the command line.
- Do not backup files, even when there is a mismatch. See Backups.