symlink man page

symlink, symlinkat — make a new name for a file

Synopsis

#include <unistd.h>

int symlink(const char *target, const char *linkpath);

#include <fcntl.h> /* Definition of AT_* constants */
#include <unistd.h>

int symlinkat(const char *target, int newdirfd, const char *linkpath);

Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

symlink():

_XOPEN_SOURCE >= 500 || _POSIX_C_SOURCE >= 200112L
|| /* Glibc versions <= 2.19: */ _BSD_SOURCE

symlinkat():

Since glibc 2.10:
_POSIX_C_SOURCE >= 200809L
Before glibc 2.10:
_ATFILE_SOURCE

Description

symlink() creates a symbolic link named linkpath which contains the string target.

Symbolic links are interpreted at run time as if the contents of the link had been substituted into the path being followed to find a file or directory.

Symbolic links may contain .. path components, which (if used at the start of the link) refer to the parent directories of that in which the link resides.

A symbolic link (also known as a soft link) may point to an existing file or to a nonexistent one; the latter case is known as a dangling link.

The permissions of a symbolic link are irrelevant; the ownership is ignored when following the link, but is checked when removal or renaming of the link is requested and the link is in a directory with the sticky bit (S_ISVTX) set.

If linkpath exists, it will not be overwritten.

symlinkat()

The symlinkat() system call operates in exactly the same way as symlink(), except for the differences described here.

If the pathname given in linkpath is relative, then it is interpreted relative to the directory referred to by the file descriptor newdirfd (rather than relative to the current working directory of the calling process, as is done by symlink() for a relative pathname).

If linkpath is relative and newdirfd is the special value AT_FDCWD, then linkpath is interpreted relative to the current working directory of the calling process (like symlink()).

If linkpath is absolute, then newdirfd is ignored.

Return Value

On success, zero is returned. On error, -1 is returned, and errno is set appropriately.

Errors

EACCES
Write access to the directory containing linkpath is denied, or one of the directories in the path prefix of linkpath did not allow search permission. (See also path_resolution(7).)
EDQUOT
The user's quota of resources on the filesystem has been exhausted. The resources could be inodes or disk blocks, depending on the filesystem implementation.
EEXIST
linkpath already exists.
EFAULT
target or linkpath points outside your accessible address space.
EIO
An I/O error occurred.
ELOOP
Too many symbolic links were encountered in resolving linkpath.
ENAMETOOLONG
target or linkpath was too long.
ENOENT
A directory component in linkpath does not exist or is a dangling symbolic link, or target or linkpath is an empty string.
ENOMEM
Insufficient kernel memory was available.
ENOSPC
The device containing the file has no room for the new directory entry.
ENOTDIR
A component used as a directory in linkpath is not, in fact, a directory.
EPERM
The filesystem containing linkpath does not support the creation of symbolic links.
EROFS
linkpath is on a read-only filesystem.

The following additional errors can occur for symlinkat():

EBADF
newdirfd is not a valid file descriptor.
ENOENT
linkpath is a relative pathname and newdirfd refers to a directory that has been deleted.
ENOTDIR
linkpath is relative and newdirfd is a file descriptor referring to a file other than a directory.

Versions

symlinkat() was added to Linux in kernel 2.6.16; library support was added to glibc in version 2.4.

Conforming to

symlink(): SVr4, 4.3BSD, POSIX.1-2001, POSIX.1-2008.

symlinkat(): POSIX.1-2008.

Notes

No checking of target is done.

Deleting the name referred to by a symbolic link will actually delete the file (unless it also has other hard links). If this behavior is not desired, use link(2).

Glibc notes

On older kernels where symlinkat() is unavailable, the glibc wrapper function falls back to the use of symlink(). When linkpath is a relative pathname, glibc constructs a pathname based on the symbolic link in /proc/self/fd that corresponds to the newdirfd argument.

See Also

ln(1), lchown(2), link(2), lstat(2), open(2), readlink(2), rename(2), unlink(2), path_resolution(7), symlink(7)

Colophon

This page is part of release 4.08 of the Linux man-pages project. A description of the project, information about reporting bugs, and the latest version of this page, can be found at https://www.kernel.org/doc/man-pages/.

Referenced By

explain(1), explain(3), explain_lca2010(1), explain_symlink(3), explain_symlink_or_die(3), fcntl(2), inotify(7), link(2), ln(1), nfslogsum(8), open(2), proc(5), readlink(2), rename(2), symlink(7), symlinks(8), syscalls(2), tar_extract_file(3).

symlinkat(2) is an alias of symlink(2).

2016-10-08 Linux Linux Programmer's Manual