Linux / Unix shred command
Source: http://www.computerhope.com/unix/shred.htm
About shred
Delete a file securely, first overwriting it to hide its contents.
shred [OPTIONS] FILE [...]
-f, –force
Change permissions to allow writing if necessary.
-n, –iterations=N
Overwrite N times instead of the default (25)
-s, –size=N
shred this many bytes (suffixes like K, M, G accepted)
-u, –remove
truncate and remove file after overwriting
-v, –verbose
show progress
-x, –exact
do not round file sizes up to the next full block; this is the default for non-regular files
-z, –zero
add a final overwrite with zeros to hide shredding
-
shred standard output
–help
display this help and exit
–version
output version information and exit
shred myfile.txt
Permanently deleted and makes the file myfile.txt unrecoverable (unless stored elsewhere or on a backup).