10.12 patch and the POSIX Standard

If you specify the `--posix' option, or set the POSIXLY_CORRECT environment variable, patch conforms 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 section 10.6 Multiple Patches in a File.

• Do not remove files that are removed by a diff. See section 10.4 Creating and Removing Files.

• Do not ask whether to get files from RCS, ClearCase, or SCCS. See section 10.2 Revision Control.

• Require that all options precede the files in the command line.

• Do not backup files, even when there is a mismatch. See section 10.8 Backup Files.