Rm

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rm (short for remove) is one of several basic Unix command lines that operates on files. It is used to delete files from a filesystem. The data is not actually destroyed. Only the index listing where the file is stored is destroyed, and the storage is made available for reuse. There are undelete utilities that will attempt to reconstruct the index and can bring the file back if the parts were not reused.

Here's example to remove a file named "foo" from a directory, here shown with the -i option:

  % rm -i foo
    remove foo? y

Options

Common options that rm accepts include:

• -r, which removes directories, removing the contents recursively beforehand (so as not to leave files without a directory to reside in) ("recursive")
• -i, which asks for every deletion to be confirmed ("interactive")
• -f, which ignores non-existent files and overrides any confirmation prompts ("force")
• -v, which shows what is being removed as it happens ("verbose")

rm is often aliased to "rm -i" so as to avoid accidental deletion of files. If a user still wishes to delete a large number of files without confirmation, they can manually cancel out the -i argument by adding the -f option (as the option specified later on the expanded command line "rm -i -f" takes precedence).

rm -rf (variously, rm -rf /, rm -rf *, and others) is frequently used in jokes and anecdotes about Unix disasters. The rm -rf variant of the command, if run by a superuser on the root directory, would cause the contents of every writable mounted filesystem on the computer to be deleted.

rm is often used in conjunction with xargs to supply a list of files to delete:

xargs rm < filelist

When rm is used on a symbolic link, it deletes the link, but does not affect the target of the link.

Permissions

Usually, on most filesystems, deleting a file requires write permission on the parent directory (and execute permission, in order to enter the directory in the first place). (Note that, confusingly for beginners, permissions on the file itself are irrelevant. However, GNU rm asks for confirmation if a write-protected file is to be deleted, unless the -f option is used.)

To delete a directory (with rm -r), one must delete all of its contents recursively. This requires that one must have read and write and execute permission to that directory (if it's not empty) and all non-empty subdirectories recursively (if there are any). The read permissions are needed to list the contents of the directory in order to delete them. This sometimes leads to an odd situation where a non-empty directory cannot be deleted because one doesn't have write permission to it and so cannot delete its contents; but if the same directory were empty, one would be able to delete it.

If a file resides in a directory with the sticky bit set, then deleting the file requires one to be the owner of the file.

Protection of /

Sun introduced "rm -rf /" protection in Solaris 10, first released in 2005. Upon executing the command, the system now reports that the removal of / is not allowed.^[1] Shortly after, the same functionality was introduced into FreeBSD version of rm utility. GNU rm refuses to execute rm -rf / if the --preserve-root option is given, which has been the default since version 6.4 of GNU Core Utilities was released in 2006.

See also

• unlink(): the underlying system call called by this user space program for its main functionality
• del (command)
• deltree

References

External links

The Wikibook Guide to Unix has a page on the topic of rm

• rm: remove directory entries – Commands & Utilities Reference, The Single UNIX® Specification, Issue 7 from The Open Group