GENWiki

SYMLINK(2) Linux Programmer's Manual SYMLINK(2)

NAME

     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 renam-
     ing 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 sym-
     link(), 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  dan-
            gling 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  direc-
            tory 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  rela-
     tive  pathname,  glibc constructs a pathname based on the symbolic link
     in /proc/self/fd that corresponds to the newdirfd argument.