PROLOG | NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | EXAMPLES | APPLICATION USAGE | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT

SYMLINK(3P)               POSIX Programmer's Manual              SYMLINK(3P)

PROLOG         top

       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.

NAME         top

       symlink, symlinkat — make a symbolic link relative to directory file
       descriptor

SYNOPSIS         top

       #include <unistd.h>

       int symlink(const char *path1, const char *path2);
       int symlinkat(const char *path1, int fd, const char *path2);

DESCRIPTION         top

       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().

RETURN VALUE         top

       Upon successful completion, these functions shall return 0.
       Otherwise, these functions shall return −1 and set errno to indicate
       the error.

ERRORS         top

       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.

EXAMPLES         top

       None.

APPLICATION USAGE         top

       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.

RATIONALE         top

       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.

FUTURE DIRECTIONS         top

       None.

SEE ALSO         top

       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)

COPYRIGHT         top

       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)