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PROLOG

       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

       symlink, symlinkat — make a symbolic link

SYNOPSIS

       #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

       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

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

ERRORS

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.

ENOENT or ENOTDIR
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.

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 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.

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

       None.

APPLICATION USAGE

       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

       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

       None.

COPYRIGHT

       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 http://www.opengroup.org/unix/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                                   2017                                       SYMLINK(3POSIX)