rm (Unix)

rm (short for remove) is a Unix command used to delete files from a filesystem.

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, 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.)

To delete a directory (with rm -r), one must delete all of its contents recursively. This requires that one must have write and execute permission to that directory (if it's not empty) and all non-empty subdirectories recursively (if there are any). 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.

Trivia

Sun introduced "rm -rf /" protection in to Solaris 10. Upon executing the command, the system now reports that the removal of / is not allowed. 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.

External links

• rm: remove directory entries – Shell and Utilities Reference, The Single UNIX Specification, Version 4 from The Open Group
• rm(1): remove files or directories – Linux User Manual – User Commands