Make a new name for a file
#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)):
_BSD_SOURCE || _XOPEN_SOURCE >= 500 || _XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED || _POSIX_C_SOURCE >= 200112L
Since glibc 2.10:
_XOPEN_SOURCE >= 700 || _POSIX_C_SOURCE >= 200809L
Before glibc 2.10:
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 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.
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.
On success, zero is returned. On error, -1 is returned, and errno is set appropriately.
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).)
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.
linkpath already exists.
target or linkpath points outside your accessible address space.
An I/O error occurred.
Too many symbolic links were encountered in resolving linkpath.
target or linkpath was too long.
A directory component in linkpath does not exist or is a dangling symbolic link, or target is the empty string.
Insufficient kernel memory was available.
The device containing the file has no room for the new directory entry.
A component used as a directory in linkpath is not, in fact, a directory.
The filesystem containing linkpath does not support the creation of symbolic links.
linkpath is on a read-only filesystem.
The following additional errors can occur for symlinkat():
newdirfd is not a valid file descriptor.
linkpath is a relative pathname and newdirfd refers to a directory that has been deleted.
linkpath is relative and newdirfd is a file descriptor referring to a file other than a directory.
symlinkat() was added to Linux in kernel 2.6.16; library support was added to glibc in version 2.4.
symlink(): SVr4, 4.3BSD, POSIX.1-2001, POSIX.1-2008.
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).
On older kernels where symlinkat() is unavailable, the glibc wrapper function falls back to the use of symlink(2). 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.
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