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SYMLINK(3P) POSIX Programmer's Manual SYMLINK(3P)
This manual page is part of the POSIX Programmer's Manual. The Linux
implementation of this interface may differ (consult the
corresponding Linux manual page for details of Linux behavior), or
the interface may not be implemented on Linux.
symlink, symlinkat — make a symbolic link relative to directory file
descriptor
#include <unistd.h>
int symlink(const char *path1, const char *path2);
int symlinkat(const char *path1, int fd, const char *path2);
The symlink() function shall create a symbolic link called path2 that
contains the string pointed to by path1 (path2 is the name of the
symbolic link created, path1 is the string contained in the symbolic
link).
The string pointed to by path1 shall be treated only as a character
string and shall not be validated as a pathname.
If the symlink() function fails for any reason other than [EIO], any
file named by path2 shall be unaffected.
If path2 names a symbolic link, symlink() shall fail and set errno to
[EEXIST].
The symbolic link's user ID shall be set to the process' effective
user ID. The symbolic link's group ID shall be set to the group ID of
the parent directory or to the effective group ID of the process.
Implementations shall provide a way to initialize the symbolic link's
group ID to the group ID of the parent directory. Implementations
may, but need not, provide an implementation-defined way to
initialize the symbolic link's group ID to the effective group ID of
the calling process.
The values of the file mode bits for the created symbolic link are
unspecified. All interfaces specified by POSIX.1‐2008 shall behave as
if the contents of symbolic links can always be read, except that the
value of the file mode bits returned in the st_mode field of the stat
structure is unspecified.
Upon successful completion, symlink() shall mark for update the last
data access, last data modification, and last file status change
timestamps of the symbolic link. Also, the last data modification and
last file status change timestamps of the directory that contains the
new entry shall be marked for update.
The symlinkat() function shall be equivalent to the symlink()
function except in the case where path2 specifies a relative path. In
this case the symbolic link is created relative to the directory
associated with the file descriptor fd instead of the current working
directory. If the file descriptor was opened without O_SEARCH, the
function shall check whether directory searches are permitted using
the current permissions of the directory underlying the file
descriptor. If the file descriptor was opened with O_SEARCH, the
function shall not perform the check.
If symlinkat() 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 symlink().
Upon successful completion, these functions shall return 0.
Otherwise, these functions shall return −1 and set errno to indicate
the error.
These functions shall fail if:
EACCES Write permission is denied in the directory where the symbolic
link is being created, or search permission is denied for a
component of the path prefix of path2.
EEXIST The path2 argument names an existing file.
EIO An I/O error occurs while reading from or writing to the file
system.
ELOOP A loop exists in symbolic links encountered during resolution
of the path2 argument.
ENAMETOOLONG
The length of a component of the pathname specified by the
path2 argument is longer than {NAME_MAX} or the length of the
path1 argument is longer than {SYMLINK_MAX}.
ENOENT A component of the path prefix of path2 does not name an
existing file or path2 is an empty string.
ENOSPC The directory in which the entry for the new symbolic link is
being placed cannot be extended because no space is left on
the file system containing the directory, or the new symbolic
link cannot be created because no space is left on the file
system which shall contain the link, or the file system is out
of file-allocation resources.
ENOTDIR
A component of the path prefix of path2 names an existing file
that is neither a directory nor a symbolic link to a
directory.
EROFS The new symbolic link would reside on a read-only file system.
The symlinkat() function shall fail if:
EACCES fd was not opened with O_SEARCH and the permissions of the
directory underlying fd do not permit directory searches.
EBADF The path2 argument does not specify an absolute path and the
fd argument is neither AT_FDCWD nor a valid file descriptor
open for reading or searching.
ENOTDIR
The path2 argument is not an absolute path and fd is a file
descriptor associated with a non-directory file.
These functions may fail if:
ELOOP More than {SYMLOOP_MAX} symbolic links were encountered during
resolution of the path2 argument.
ENAMETOOLONG
The length of the path2 argument exceeds {PATH_MAX} or
pathname resolution of a symbolic link in the path2 argument
produced an intermediate result with a length that exceeds
{PATH_MAX}.
The following sections are informative.
None.
Like a hard link, a symbolic link allows a file to have multiple
logical names. The presence of a hard link guarantees the existence
of a file, even after the original name has been removed. A symbolic
link provides no such assurance; in fact, the file named by the path1
argument need not exist when the link is created. A symbolic link can
cross file system boundaries.
Normal permission checks are made on each component of the symbolic
link pathname during its resolution.
The purpose of the symlinkat() function is to create symbolic links
in directories other than the current working directory without
exposure to race conditions. Any part of the path of a file could be
changed in parallel to a call to symlink(), resulting in unspecified
behavior. By opening a file descriptor for the target directory and
using the symlinkat() function it can be guaranteed that the created
symbolic link is located relative to the desired directory.
None.
fdopendir(3p), fstatat(3p), lchown(3p), link(3p), open(3p),
readlink(3p), rename(3p), unlink(3p)
The Base Definitions volume of POSIX.1‐2008, unistd.h(0p)
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2013 Edition, Standard for Information
Technology -- Portable Operating System Interface (POSIX), The Open
Group Base Specifications Issue 7, Copyright (C) 2013 by the
Institute of Electrical and Electronics Engineers, Inc and The Open
Group. (This is POSIX.1-2008 with the 2013 Technical Corrigendum 1
applied.) In the event of any discrepancy between this version and
the original IEEE and The Open Group Standard, the original IEEE and
The Open Group Standard is the referee document. The original
Standard can be obtained online at http://www.unix.org/online.html .
Any typographical or formatting errors that appear in this page are
most likely to have been introduced during the conversion of the
source files to man page format. To report such errors, see
https://www.kernel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group 2013 SYMLINK(3P)
Pages that refer to this page: unistd.h(0p), fdopendir(3p), fstatat(3p), lchown(3p), link(3p), open(3p), readdir(3p), readlink(3p), rename(3p), unlink(3p)