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UNLINK(2) System Calls Manual UNLINK(2)

unlink, unlinkat — remove directory entry

library “libc”

#include <unistd.h>

int
unlink(const char *path);

#include <fcntl.h>

int
unlinkat(int fd, const char *path, int flag);

The () function removes the link named by path from its directory and decrements the link count of the file which was referenced by the link. If that decrement reduces the link count of the file to zero, and no process has the file open, then all resources associated with the file are reclaimed. If one or more process have the file open when the last link is removed, the link is removed, but the removal of the file is delayed until all references to it have been closed.

() works the same way as unlink() except if path is relative. In that case, it is looked up from a directory whose file descriptor was passed as fd. Search permission is required on this directory. fd can be set to AT_FDCWD in order to specify the current directory.

() will remove directories just like rmdir(2), provided AT_REMOVEDIR is set in flag.

The unlink() and unlinkat() functions return the value 0 if successful; otherwise the value -1 is returned and the global variable errno is set to indicate the error.

The unlink() and unlinkat() functions succeed unless:

[]
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.
[]
The entry to be unlinked is the mount point for a mounted file system.
[]
path points outside the process's allocated address space.
[]
An I/O error occurred while deleting the directory entry or deallocating the inode.
[]
Too many symbolic links were encountered in translating the pathname.
[]
A component of a pathname exceeded {NAME_MAX} characters, or an entire path name exceeded {PATH_MAX} characters.
[]
The named file does not exist.
[]
A component of the path prefix is not a directory.
[]
The named file is a directory and the effective user ID of the process is not the super-user, the file system containing the file does not permit the use of unlink() on a directory, or the directory containing the file is marked sticky, and neither the containing directory nor the file to be removed are owned by the effective user ID.
[]
The named file resides on a read-only file system.

In addition, unlinkat() will fail if:

[]
path does not specify an absolute path and fd is neither AT_FDCWD nor a valid file descriptor open for reading or searching.
[]
path is not an absolute path and fd is a file descriptor associated with a non-directory file; or flag has AT_REMOVEDIR set and path does not name a directory.
[]
flag has AT_REMOVEDIR set and path is a directory that is not empty.

close(2), link(2), rmdir(2), symlink(7)

The unlink() function conforms to IEEE Std 1003.1-1990 (“POSIX.1”). unlinkat() conforms to IEEE Std 1003.1-2008 (“POSIX.1”).

An unlink() function call appeared in Version 1 AT&T UNIX.

September 2, 2019 NetBSD-9.2