patch renames an original input file into a backup
file by appending to its name the extension ‘.orig’, or ‘~’
if using ‘.orig’ would make the backup file name too
long.1 The -z backup-suffix or
--suffix=backup-suffix option causes
use backup-suffix as the backup extension instead.
Alternately, you can specify the extension for backup files with the
SIMPLE_BACKUP_SUFFIX environment variable, which the options
patch can also create numbered backup files the way
GNU Emacs does. With this method, instead of having a
single backup of each file,
patch makes a new backup file
name each time it patches a file. For example, the backups of a file
named sink would be called, successively, sink.~1~,
sink.~2~, sink.~3~, etc.
The -V backup-style or
--version-control=backup-style option takes as an
argument a method for creating backup file names. You can alternately
control the type of backups that
patch makes with the
PATCH_VERSION_CONTROL environment variable, which the
-V option overrides. If
PATCH_VERSION_CONTROL is not
VERSION_CONTROL environment variable is used instead.
Please note that these options and variables control backup file
names; they do not affect the choice of revision control system
(see Revision Control).
The values of these environment variables and the argument to the
-V option are like the GNU Emacs
variable (see Backup Names in The GNU Emacs Manual,
for more information on backup versions in Emacs). They also
recognize synonyms that are more descriptive. The valid values are
listed below; unique abbreviations are acceptable.
Always make numbered backups.
Make numbered backups of files that already have them, simple backups of the others. This is the default.
Always make simple backups.
You can also tell
patch to prepend a prefix, such as a
directory name, to produce backup file names. The
--prefix=prefix (-B prefix) option makes backup
files by prepending prefix to them. The
--basename-prefix=prefix (-Y prefix) prepends
prefix to the last file name component of backup file names
instead; for example, -Y ~ causes the backup name for
dir/file.c to be dir/~file.c. If you use either of
these prefix options, the suffix-based options are ignored.
If you specify the output file with the -o option, that file is the one that is backed up, not the input file.
Options that affect the names of backup files do not affect whether backups are made. For example, if you specify the --no-backup-if-mismatch option, none of the options described in this section have any affect, because no backups are made.
A coding error in GNU
2.5.4 causes it to always use ‘~’, but this should be fixed in
the next release.