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man pages section 2: System Calls

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Updated: Thursday, June 13, 2019
 
 

unlinkat(2)

Name

unlink, unlinkat - remove directory entry

Synopsis

#include <unistd.h>

int unlink(const char *path);
int unlinkat(int dirfd, const char *path, int flag);

Description

The unlink() function removes a link to a file. If path names a symbolic link, unlink() removes the symbolic link named by path and does not affect any file or directory named by the contents of the symbolic link. Otherwise, unlink() removes the link named by the pathname pointed to by path and decrements the link count of the file referenced by the link.

The unlinkat() function also removes a link to a file. See fsattr(7). If the flag argument is 0, the behavior of unlinkat() is the same as unlink() except in the processing of its path argument. If path is absolute, unlinkat() behaves the same as unlink() and the dirfd argument is unused. If path is relative and dirfd has the value AT_FDCWD, defined in <fcntl.h>, unlinkat() also behaves the same as unlink(). Otherwise, path is resolved relative to the directory referenced by the dirfd argument.

If the flag argument is set to the value AT_REMOVEDIR, defined in <fcntl.h>, unlinkat() behaves the same as rmdir(2) except in the processing of the path argument as described above.

When the file's link count becomes 0 and no process has the file open, the space occupied by the file will be freed and the file is no longer accessible. If one or more processes have the file open when the last link is removed, the link is removed before unlink() or unlinkat() returns, but the removal of the file contents is postponed until all references to the file are closed.

If the path argument is a directory and the filesystem supports unlink() and unlinkat() on directories, the directory is unlinked from its parent with no cleanup being performed. In UFS, the disconnected directory will be found the next time the filesystem is checked with fsck(8). The unlink() and unlinkat() functions will not fail simply because a directory is not empty. The user with appropriate privileges can orphan a non-empty directory without generating an error message.

If the path argument is a directory, the call will fail with errno set to EPERM.

Upon successful completion, unlink() and unlinkat() will mark for update the st_ctime and st_mtime fields of the parent directory. If the file's link count is not 0, the st_ctime field of the file will be marked for update.

Return Values

Upon successful completion, 0 is returned. Otherwise, −1 is returned, errno is set to indicate the error, and the file is not unlinked.

Errors

The unlink() and unlinkat() functions will fail if:

EACCES

Search permission is denied for a component of the path prefix, or write permission is denied on the directory containing the link to be removed.

EACCES

The parent directory has the sticky bit set and the file is not writable by the user, the user does not own the parent directory, the user does not own the file, and the user is not a privileged user.

EBUSY

The entry to be unlinked is the mount point for a mounted file system, or a previously unlinked NFS file waiting for references to be released.

EFAULT

The path argument points to an illegal address.

EILSEQ

The path argument includes non-UTF8 characters and the file system accepts only file names where all characters are part of the UTF-8 character codeset.

EINTR

A signal was caught during the execution of the unlink() function.

ELOOP

Too many symbolic links were encountered in translating path.

ENAMETOOLONG

The length of the path argument exceeds PATH_MAX, or the length of a path component exceeds NAME_MAX while _POSIX_NO_TRUNC is in effect.

ENOENT

The named file does not exist or is a null pathname.

ENOLINK

The path argument points to a remote machine and the link to that machine is no longer active.

ENOTDIR

A component of the path prefix is not a directory or the provided directory descriptor for unlinkat() is not AT_FDCWD or does not reference a directory.

EPERM

The named file is a directory; the implementation does not support unlink() or unlinkat() on directories.

EROFS

The directory entry to be unlinked is part of a read-only file system.

The unlink() and unlinkat() functions may fail if:

ENAMETOOLONG

Pathname resolution of a symbolic link produced an intermediate result whose length exceeds {PATH_MAX}.

ETXTBSY

The entry to be unlinked is the last directory entry to a pure procedure (shared text) file that is being executed.

Usage

Applications should use rmdir(2) to remove a directory.

Attributes

See attributes(7) for descriptions of the following attributes:

ATTRIBUTE TYPE
ATTRIBUTE VALUE
Interface Stability
Committed
MT-Level
Async-Signal-Safe

See Also

rm(1), close(2), link(2), open(2), rmdir(2), remove(3C), attributes(7), fsattr(7), privileges(7)