coreutils: Backup options

 
 2.2 Backup options
 ==================
 
 Some GNU programs (at least ‘cp’, ‘install’, ‘ln’, and ‘mv’) optionally
 make backups of files before writing new versions.  These options
 control the details of these backups.  The options are also briefly
 mentioned in the descriptions of the particular programs.
 
 ‘-b’
 ‘--backup[=METHOD]’
      Make a backup of each file that would otherwise be overwritten or
      removed.  Without this option, the original versions are destroyed.
      Use METHOD to determine the type of backups to make.  When this
      option is used but METHOD is not specified, then the value of the
      ‘VERSION_CONTROL’ environment variable is used.  And if
      ‘VERSION_CONTROL’ is not set, the default backup type is
      ‘existing’.
 
      Note that the short form of this option, ‘-b’ does not accept any
      argument.  Using ‘-b’ is equivalent to using ‘--backup=existing’.
 
      This option corresponds to the Emacs variable ‘version-control’;
      the values for METHOD are the same as those used in Emacs.  This
      option also accepts more descriptive names.  The valid METHODs are
      (unique abbreviations are accepted):
 
      ‘none’
      ‘off’
           Never make backups.
 
      ‘numbered’
      ‘t’
           Always make numbered backups.
 
      ‘existing’
      ‘nil’
           Make numbered backups of files that already have them, simple
           backups of the others.
 
      ‘simple’
      ‘never’
           Always make simple backups.  Please note ‘never’ is not to be
           confused with ‘none’.
 
 ‘-S SUFFIX’
 ‘--suffix=SUFFIX’
      Append SUFFIX to each backup file made with ‘-b’.  If this option
      is not specified, the value of the ‘SIMPLE_BACKUP_SUFFIX’
      environment variable is used.  And if ‘SIMPLE_BACKUP_SUFFIX’ is not
      set, the default is ‘~’, just as in Emacs.