Linux man pages : link (2)
LINK(2) Linux Programmer's Manual LINK(2)
link - make a new name for a file
int link(const char *oldpath, const char *newpath);
link creates a new link (also known as a hard link) to an existing
If newpath exists it will not be overwritten.
This new name may be used exactly as the old one for any operation;
both names refer to the same file (and so have the same permissions and
ownership) and it is impossible to tell which name was the `original'.
On success, zero is returned. On error, -1 is returned, and errno is
EXDEV oldpath and newpath are not on the same filesystem.
EPERM The filesystem containing oldpath and newpath does not support
the creation of hard links.
EFAULT oldpath or newpath points outside your accessible address space.
EACCES Write access to the directory containing newpath is not allowed
for the process's effective uid, or one of the directories in
oldpath or newpath did not allow search (execute) permission.
oldpath or newpath was too long.
ENOENT A directory component in oldpath or newpath does not exist or is
a dangling symbolic link.
A component used as a directory in oldpath or newpath is not, in
fact, a directory.
ENOMEM Insufficient kernel memory was available.
EROFS The file is on a read-only filesystem.
EEXIST newpath already exists.
EMLINK The file referred to by oldpath already has the maximum number
of links to it.
ELOOP Too many symbolic links were encountered in resolving oldpath or
ENOSPC The device containing the file has no room for the new directory
EPERM oldpath is a directory.
EIO An I/O error occurred.
Hard links, as created by link, cannot span filesystems. Use symlink if
this is required.
SVr4, SVID, POSIX, BSD 4.3, X/OPEN. SVr4 documents additional ENOLINK
and EMULTIHOP error conditions; POSIX.1 does not document ELOOP.
X/OPEN does not document EFAULT, ENOMEM or EIO.
On NFS file systems, the return code may be wrong in case the NFS
server performs the link creation and dies before it can say so. Use
stat(2) to find out if the link got created.
symlink(2), unlink(2), rename(2), open(2), stat(2), ln(1)
Linux 2.0.30 1997-12-10 LINK(2)