overwrite specified files
purge [ -f ] [ -r ] [ -v ] [ -m num ] [ -suo ] [ -t type ] ... [ -z ] [ files ] ...
The purge command is used to overwrite various parts of the system.
It overwrites files specified on the command line, or those listed in
a policy file maintained by the system administrator.
The policy file defines types of files and devices which are
purged as a group. The utility can be used to purge
or other devices like magnetic tapes and floppies.
An option even exists to zero memory.
After purge is run, no data remains on the specified device or file.
After being overwritten,
may be used to verify that no data remains on the device
or in the file.
When files are overwritten multiple times, the first pass writes
binary zeros. Subsequent passes alternate writing
binary ones and binary zeros.
The optional flags are outlined below:
Similarly to regular files, most special files can be
purged by being placed in the policy file or with the command
Block special files and some character special files can
The console, ttys, printers and other ``infinite output''
devices cannot be purged with this command. Disks, floppies and
magnetic tapes can be overwritten.
Tape devices are first erased once and then overwritten the
specified number of times.
Do not warn about files which
are not present or inaccessible. Attempts to purge a floppy
which is inaccessible (for example, the door is open) will always generate a
diagnostic on the system console.
Recursively purge directories. Without this flag no action is taken upon
Verbose operation, list the name of each file as it is
Overwrite each file num times.
Overwrite files and devices designated as ``system'' in the
policy file. (Equivalent to -tsystem.)
Overwrite files and devices designated as ``user'' in the
policy file. (Equivalent to -tuser.)
Overwrite other (non-system and non-user) files and filesystems.
This purges all entries in the policy file which are not of either
type system or user. This flag, by the nature of its
implicit definition, has no -t equivalent.
Overwrite the files identified in the policy file as being part of group
Writes binary zeroes to system memory,
including memory buffers of intelligent devices (that is, disk
controller cache, etc.). This will close down the system
immediately. This should only be done from single-user mode,
or when no users are logged on.
The system will autoboot if so configured (see
Only the super user may use this option.
Regular, directory or special files to purge.
When both types and files are specified on
the command line, all of the indicated files
are overwritten by the utility. In particular, first the files
selected from the policy file, and then those
specified on the command line, are overwritten.
Each line in the policy file (/etc/default/purge) designates
a file, filesystem or device as a member of some type. The
syntax of a line is:
file type [ count ]
The optional count field is the number of times to overwrite
The default count is one.
The utility will overwrite file any time the command
purge -t type
Blank lines in the policy file and lines beginning with ``#''
purge: warning: invalid entry in policy file (line n
An invalid line was read from the policy file where n is the
number of the incorrectly formatted line.
is a directory
If the -r switch is not specified no action is taken upon
directories and this diagnostic is displayed.
purge: only the superuser can zero memory
This message is displayed when a user other than the super user
tries to use the -z option.
the policy file
purge is not part of any currently supported
standard; it is an extension of AT&T System V
provided by The Santa Cruz Operation, Inc.
© 2003 Caldera International, Inc. All rights reserved.
SCO OpenServer Release 5.0.7 -- 11 February 2003