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link(2)

link(2)                          System Calls                          link(2)

NAME
       link, linkat - link to a file

SYNOPSIS
       #include <unistd.h>

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


       int linkat(int fd1, const char *path1, int fd2, const char *path2,
            int flag);

DESCRIPTION
       The  link()  function creates a new hard link (directory entry) for the
       existing file and increments its link count by one. The path1  argument
       provides  the pathname of an existing file. The path2 argument provides
       the pathname of the new directory entry to be created.


       To create hard links, both files must be on the same file system.  Both
       the  old and the new link share equal access and rights to the underly‐
       ing object. Hard links to directories are not allowed. The  file  named
       by path1 must not be a directory.


       Upon  successful completion, link() marks for update the st_ctime field
       of the file. Also, the st_ctime and st_mtime fields  of  the  directory
       that contains the new entry are marked for update.


       If  link() fails, no link is created and the link count of the file re‐
       mains unchanged.


       The linkat() function is equivalent to link() except in the case  where
       either  path1 or path2 or both are relative paths. In this case a rela‐
       tive path path1 is interpreted relative  to  the  directory  associated
       with  the  file descriptor fd1 instead of the current working directory
       and similarly for path2 and the file descriptor fd2. If  the  file  de‐
       scriptor  was  opened without O_SEARCH, the function checks whether di‐
       rectory searches are permitted using the current permissions of the di‐
       rectory underlying the file descriptor.  If  the  file  descriptor  was
       opened with O_SEARCH, the function does not perform the check.


       The  fd1  and fd2 arguments to linkat() can be set to the special value
       AT_FDCWD, specifying that the corresponding path argument is to be  in‐
       terpreted  relative to the current working directory, the same behavior
       provided by link().


       Values for flag are constructed by a bitwise-inclusive OR of flags from
       the following list, defined in <fcntl.h>.

       AT_SYMLINK_FOLLOW    If path1 names a symbolic link, a new link for the
                            target of the symbolic link is created.



       If the AT_SYMLINK_FOLLOW flag is clear in the  flag  argument  and  the
       path1  argument  names  a  symbolic link, a new link is created for the
       symbolic link path1 and not its target.

RETURN VALUES
       Upon successful completion, 0 is returned. Otherwise, −1  is  returned,
       no link is created, and errno is set to indicate the error.

ERRORS
       The link() and linkat() functions will fail if:

       EACCES          A component of either path prefix denies search permis‐
                       sion,  or  the requested link requires writing in a di‐
                       rectory with a mode that denies write permission.


       EDQUOT          The directory where the entry for the new link is being
                       placed cannot be extended because the user's  quota  of
                       disk blocks on that file system has been exhausted.


       EEXIST          The link named by path2 exists.


       EFAULT          The  path1  or  path2 argument points to an illegal ad‐
                       dress.


       EILSEQ          The path argument includes non-UTF8 characters and  the
                       file  system  accepts only file names where all charac‐
                       ters are part of the UTF-8 character codeset.


       EINTR           A signal was caught during the execution of the  link()
                       function.


       ELOOP           Too many symbolic links were encountered in translating
                       path.


       EMLINK          The  maximum  number  of  links  to a file would be ex‐
                       ceeded.


       ENAMETOOLONG    The length of  the  path1  or  path2  argument  exceeds
                       PATH_MAX,  or  the length of a path1 or path2 component
                       exceeds NAME_MAX while _POSIX_NO_TRUNC is in effect.


       ENOENT          The path1 or path2 argument is a null pathname; a  com‐
                       ponent  of  either  path  prefix does not exist; or the
                       file named by path1 does not exist.


       ENOLINK         The path1 or path2 argument points to a remote  machine
                       and the link to that machine is no longer active.


       ENOSPC          The directory that would contain the link cannot be ex‐
                       tended.


       ENOTDIR         A component of either path prefix is not a directory.


       EPERM           The  file named by path1 is a directory; the Oracle So‐
                       laris implementation prohibits links to directories.

                       The effective user ID does not match the owner  of  the
                       file  and the {PRIV_FILE_LINK_ANY} privilege is not as‐
                       serted in the effective set of the calling process.


       EROFS           The requested link requires writing in a directory on a
                       read-only file system.

                       The file named by path1 is  read-only  because  of  the
                       mwac(7) policy.


       EXDEV           The link named by path2 and the file named by path1 are
                       on different logical devices (file systems).



       The linkat() function will fail if:

       EBADF    The  path1 or path2 argument does not specify an absolute path
                and the fd1 or fd2 argument, respectively, is neither AT_FDCWD
                nor a valid file descriptor open for reading.



       The link() and linkat() functions may fail if:

       ELOOP           More than {SYMLOOP_MAX} symbolic links were encountered
                       during resolution of the path1 or path2 argument.


       ENAMETOOLONG    The length of a pathname exceeds {PATH_MAX},  or  path‐
                       name resolution of a symbolic link produced an interme‐
                       diate result with a length that exceeds {PATH_MAX}.


       EXDEV           The link named by path2 and the file named by path1 are
                       on different logical devices (file systems).



       The linkat() function may fail if:

       EINVAL     The value of the flag argument is not valid.


       ENOTDIR    The  path1 or path2 argument is not an absolute path and fd1
                  or fd2, respectively, is neither AT_FDCWD  nor  a  file  de‐
                  scriptor associated with a directory.


ATTRIBUTES
       See attributes(7) for descriptions of the following attributes:

       tab()  box; cw(2.75i) |cw(2.75i) lw(2.75i) |lw(2.75i) ATTRIBUTE TYPEAT‐
       TRIBUTE VALUE _ Interface  StabilityCommitted  _  MT-LevelAsync-Signal-
       Safe _ StandardSee standards(7).


SEE ALSO
       symlink(2),  unlink(2),  mwac(7),  attributes(7),  privileges(7), stan‐
       dards(7)

HISTORY
       The linkat() function and AT_SYMLINK_FOLLOW flag were added to  Solaris
       in the Solaris 11.0 release.


       The link() function has been included in all Sun and Oracle releases of
       Solaris.

Oracle Solaris 11.4               30 Jan 2023                          link(2)
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