Ubuntu Manpage: symlink, symlinkat - make a new name for a file

NAME

       symlink, symlinkat - make a new name for a file

LIBRARY

       Standard C library (libc, -lc)

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 <= 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 (except when the protected_symlinks feature is enabled, as explained in proc(5)),
       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.

       See openat(2) for an explanation of the need for symlinkat().

RETURN VALUE

       On  success, zero is returned.  On error, -1 is returned, and errno is set to indicate the
       error.

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).)

EBADF (symlinkat()) linkpath is relative but newdirfd is neither AT_FDCWD nor a valid
file descriptor.

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.

ENOENT (symlinkat()) linkpath is a relative pathname and newdirfd refers to a directory
that has been deleted.

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.

ENOTDIR
(symlinkat()) linkpath is relative and newdirfd is a file descriptor referring to a
file other than a directory.

EPERM The filesystem containing linkpath does not support the creation of symbolic links.

EROFS linkpath is on a read-only filesystem.

VERSIONS

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

STANDARDS

       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.