symlink(3p) — Linux manual page


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

SYNOPSIS         top

       #include <unistd.h>

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

       #include <fcntl.h>

       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 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 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.

       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.

              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.

              The path2 argument contains at least one non-<slash>
              character and ends with one or more trailing <slash>
              characters. If path2 without the trailing <slash>
              characters would name an existing file, an [ENOENT] error
              shall not occur.

       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.

              A component of the path prefix of path2 names an existing
              file that is neither a directory nor a symbolic link to a

       EROFS  The new symbolic link would reside on a read-only file

       The symlinkat() 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 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.

              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.

              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



       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.



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.1‐2017, fcntl.h(0p),

COPYRIGHT         top

       Portions of this text are reprinted and reproduced in electronic
       form from IEEE Std 1003.1-2017, Standard for Information
       Technology -- Portable Operating System Interface (POSIX), The
       Open Group Base Specifications Issue 7, 2018 Edition, Copyright
       (C) 2018 by the Institute of Electrical and Electronics
       Engineers, Inc and The Open Group.  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 .

       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 .

IEEE/The Open Group               2017                       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)