phoenix-rtos-doc / libc / functions / u / unlink.part-impl.md

Synopsis

#include <unistd.h>

int unlink(const char *path);

#include <fcntl.h>

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

Status

Partially implemented

Conformance

IEEE Std 1003.1-2017

Description

The unlink() function shall remove a link to a file. If path names a symbolic link, unlink() shall remove the symbolic link named by path and shall not affect any file or directory named by the contents of the symbolic link. Otherwise, unlink() shall remove the link named by the path name pointed to by path and shall decrement the link count of the file referenced by the link.

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

The path argument shall not name a directory unless the process has appropriate privileges and the implementation supports using unlink() on directories.

Upon successful completion, unlink() shall mark for update the last data modification and last file status change timestamps of the parent directory. Also, if the file's link count is not 0, the last file status change timestamp of the file shall be marked for update.

The unlinkat() function shall be equivalent to the unlink() or rmdir() function except in the case where path specifies a relative path. In this case the directory entry to be removed is determined relative to the directory associated with the file descriptor fd instead of the current working directory. If the access mode of the open file description associated with the file descriptor is not O_SEARCH, the function shall check whether directory searches are permitted using the current permissions of the directory underlying the file descriptor. If the access mode is O_SEARCH, the function shall not perform the check.

Values for flag are constructed by a bitwise-inclusive OR of flags from the following list, defined in <fcntl.h>:

AT_REMOVEDIR - remove the directory entry specified by fd and path as a directory, not a normal file.

If unlinkat() is passed the special value AT_FDCWD in the fd parameter, the current working directory shall be used and the behavior shall be identical to a call to unlink() or rmdir() respectively, depending on whether the AT_REMOVEDIR bit is set in flag.

Return value

Upon successful completion, these functions shall return 0. Otherwise, these functions shall return -1 and set errno to indicate the error. If -1 is returned, the named file shall not be changed.

Errors

These functions shall fail and shall not unlink the file if:

EACCES - Search permission is denied for a component of the path prefix, or write permission is denied on the directory containing the directory entry to be removed.
EBUSY - The file named by the path argument cannot be unlinked because it is being used by the system or another process and the implementation considers this an error.
ELOOP - A loop exists in symbolic links encountered during resolution of the path argument.
ENAMETOOLONG - The length of a component of a path name is longer than NAME_MAX.
ENOENT - A component of path does not name an existing file or path is an empty string.
ENOTDIR - A component of the path prefix names an existing file that is neither a directory nor a symbolic link to a directory, or the path argument contains at least one non-<slash> character and ends with one or more trailing <slash> characters and the last path name component names an existing file that is neither a directory nor a symbolic link to a directory.
EPERM - The file named by path is a directory, and either the calling process does not have appropriate privileges, or the implementation prohibits using unlink() on directories.
EPERM or EACCES - The S_ISVTX flag is set on the directory containing the file referred to by the path argument and the process does not satisfy the criteria specified in XBD Directory Protection.
EROFS - The directory entry to be unlinked is part of a read-only file system.

The unlinkat() function shall fail if:

EACCES - The access mode of the open file description associated with fd is not O_SEARCH and the permissions of the directory underlying fd do not permit directory searches.
EBADF - The path argument does not specify an absolute path and the fd argument is neither AT__fd_CWD nor a valid file descriptor open for reading or searching.
ENOTDIR - The path argument is not an absolute path and fd is a file descriptor associated with a non-directory file.
EEXIST or ENOTEMPTY - The flag parameter has the AT_REMOVEDIR bit set and the path argument names a directory that is not an empty directory, or there are hard links to the directory other than dot or a single entry in dot-dot.
ENOTDIR - The flag parameter has the AT_REMOVEDIR bit set and path does not name a directory.

These functions may fail and not unlink the file if:

EBUSY - The file named by path is a named STREAM.
ELOOP - More than SYMLOOP_MAX symbolic links were encountered during resolution of the path argument.
ENAMETOOLONG - The length of a path name exceeds PATH_MAX, or path name resolution of a symbolic link produced an intermediate result with a length that 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.

The unlinkat() function may fail if:

EINVAL - The value of the flag argument is not valid.

Tests

Untested

Known bugs

None