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(diff.info)Backups

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Backup File Names
=================

   Normally, `patch' renames an original input file into a backup file
by appending to its name the extension `.orig', or `~' on systems that
do not support long file names.  The `-b BACKUP-SUFFIX' or
`--suffix=BACKUP-SUFFIX' option uses 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 override.

   `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
`VERSION_CONTROL' environment variable, which the `-V' option
overrides.  The value of the `VERSION_CONTROL' environment variable and
the argument to the `-V' option are like the GNU Emacs
`version-control' variable (Note: emacs., 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.

`t'
`numbered'
     Always make numbered backups.

`nil'
`existing'
     Make numbered backups of files that already have them, simple
     backups of the others.  This is the default.

`never'
`simple'
     Always make simple backups.

   Alternately, you can tell `patch' to prepend a prefix, such as a
directory name, to produce backup file names.  The `-B BACKUP-PREFIX'
or `--prefix=BACKUP-PREFIX' option makes backup files by prepending
BACKUP-PREFIX to them.  If you use this option, `patch' ignores any
`-b' option that you give.

   If the backup file already exists, `patch' creates a new backup file
name by changing the first lowercase letter in the last component of
the file name into uppercase.  If there are no more lowercase letters
in the name, it removes the first character from the name.  It repeats
this process until it comes up with a backup file name that does not
already exist.

   If you specify the output file with the `-o' option, that file is
the one that is backed up, not the input file.