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Add caution about effectiveness to help text

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Fort 2015-12-30 09:22:21 -08:00
parent eb6453013e
commit 6c3917e123
1 changed files with 43 additions and 9 deletions
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50
src/shred/shred.rs
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@ -208,14 +208,7 @@ pub fn uumain(args: Vec<String>) -> i32 {
};
if matches.opt_present("help") {
println!("Usage: {} [OPTION]... FILE...", NAME);
println!("Overwrite the specified FILE(s) repeatedly, in order to make it harder \
for even very expensive hardware probing to recover the data.");
println!("{}", opts.usage(""));
println!("Delete FILE(s) if --remove (-u) is specified. The default is not to remove");
println!("the files because it is common to operate on device files like /dev/hda,");
println!("and those files usually should not be removed.");
println!("");
show_help(&opts);
return 0;
} else if matches.opt_present("version") {
println!("{} {}", NAME, VERSION_STR);
@ -249,6 +242,47 @@ pub fn uumain(args: Vec<String>) -> i32 {
0
}
fn show_help(opts: &getopts::Options) {
println!("Usage: {} [OPTION]... FILE...", NAME);
println!("Overwrite the specified FILE(s) repeatedly, in order to make it harder \
for even very expensive hardware probing to recover the data.");
println!("{}", opts.usage(""));
println!("Delete FILE(s) if --remove (-u) is specified. The default is not to remove");
println!("the files because it is common to operate on device files like /dev/hda,");
println!("and those files usually should not be removed.");
println!("");
println!("CAUTION: Note that {} relies on a very important assumption:", NAME);
println!("that the file system overwrites data in place. This is the traditional");
println!("way to do things, but many modern file system designs do not satisfy this");
println!("assumption. The following are examples of file systems on which {} is", NAME);
println!("not effective, or is not guaranteed to be effective in all file system modes:");
println!("");
println!("* log-structured or journaled file systems, such as those supplied with");
println!("AIX and Solaris (and JFS, ReiserFS, XFS, Ext3, etc.)");
println!("");
println!("* file systems that write redundant data and carry on even if some writes");
println!("fail, such as RAID-based file systems");
println!("");
println!("* file systems that make snapshots, such as Network Appliance's NFS server");
println!("");
println!("* file systems that cache in temporary locations, such as NFS");
println!("version 3 clients");
println!("");
println!("* compressed file systems");
println!("");
println!("In the case of ext3 file systems, the above disclaimer applies");
println!("(and {} is thus of limited effectiveness) only in data=journal mode,", NAME);
println!("which journals file data in addition to just metadata. In both the");
println!("data=ordered (default) and data=writeback modes, {} works as usual.", NAME);
println!("Ext3 journaling modes can be changed by adding the data=something option");
println!("to the mount options for a particular file system in the /etc/fstab file,");
println!("as documented in the mount man page (man mount).");
println!("");
println!("In addition, file system backups and remote mirrors may contain copies");
println!("of the file that cannot be removed, and that will allow a shredded file");
println!("to be recovered later.");
}
// TODO: Add support for all postfixes here up to and including EiB
// http://www.gnu.org/software/coreutils/manual/coreutils.html#Block-size
fn get_size(size_str_opt: Option<String>) -> Option<u64> {