14.6 Deleting Files

You can delete a file with unlink or remove.

Deletion actually deletes a file name. If this is the file’s only name, then the file is deleted as well. If the file has other remaining names (see Hard Links), it remains accessible under those names.

Function: int unlink (const char *filename)

Preliminary: | MT-Safe | AS-Safe | AC-Safe | See POSIX Safety Concepts.

The unlink function deletes the file name filename. If this is a file’s sole name, the file itself is also deleted. (Actually, if any process has the file open when this happens, deletion is postponed until all processes have closed the file.)

The function unlink is declared in the header file unistd.h.

This function returns 0 on successful completion, and -1 on error. In addition to the usual file name errors (see File Name Errors), the following errno error conditions are defined for this function:

EACCES

Write permission is denied for the directory from which the file is to be removed, or the directory has the sticky bit set and you do not own the file.

EBUSY

This error indicates that the file is being used by the system in such a way that it can’t be unlinked. For example, you might see this error if the file name specifies the root directory or a mount point for a file system.

ENOENT

The file name to be deleted doesn’t exist.

EPERM

On some systems unlink cannot be used to delete the name of a directory, or at least can only be used this way by a privileged user. To avoid such problems, use rmdir to delete directories. (On GNU/Linux and GNU/Hurd systems unlink can never delete the name of a directory.)

EROFS

The directory containing the file name to be deleted is on a read-only file system and can’t be modified.

Function: int rmdir (const char *filename)

Preliminary: | MT-Safe | AS-Safe | AC-Safe | See POSIX Safety Concepts.

The rmdir function deletes a directory. The directory must be empty before it can be removed; in other words, it can only contain entries for . and ...

In most other respects, rmdir behaves like unlink. There are two additional errno error conditions defined for rmdir:

ENOTEMPTY

EEXIST

The directory to be deleted is not empty.

These two error codes are synonymous; some systems use one, and some use the other. GNU/Linux and GNU/Hurd systems always use ENOTEMPTY.

The prototype for this function is declared in the header file unistd.h.

Function: int remove (const char *filename)

Preliminary: | MT-Safe | AS-Safe | AC-Safe | See POSIX Safety Concepts.

This is the ISO C function to remove a file. It works like unlink for files and like rmdir for directories. remove is declared in stdio.h.