readlink - read the contents of a symbolic link
#include <unistd.h>
ssize_t readlink(const char *restrict path,
char *restrict buf, size_t bufsiz);
ssize_t readlinkat(int fd, const char *restrict path,
char *restrict buf, size_t bufsiz);
The readlink() and readlinkat() functions place the contents of
the symbolic link referred to by path in the buffer buf which
has size bufsiz. If the number of bytes in the symbolic link is less
than bufsiz, the contents of the remainder of buf are left
unchanged. If the buf argument is not large enough to contain the link
content, the first bufsize bytes are placed in buf.
The realinkat() function behaves similarly to
readlink(); however, when path is a relative path, it is
resolved relative to the directory referred to by fd. To use the
current working directory, fd should be the special value
AT_FDCWD.
Upon successful completion, readlink() and readlinkat() return the
count of bytes placed in the buffer. Otherwise, they returns −1,
leave the buffer unchanged, and set errno to indicate the error.
The readlink() and readlinkat() functions will fail if:
EACCES
Search permission is denied for a component of the path
prefix of path.
EFAULT
path or buf points to an illegal
address.
EINVAL
The path argument names a file that is not a
symbolic link.
EIO
An I/O error occurred while reading from the file
system.
ENOENT
A component of path does not name an existing file
or path is an empty string.
ELOOP
A loop exists in symbolic links encountered during
resolution of the path argument.
ENAMETOOLONG
The length of path exceeds {PATH_MAX}, or a
pathname component is longer than {NAME_MAX} while
_POSIX_NO_TRUNC is in effect.
ENOTDIR
A component of the path prefix is not a directory. For
readlinkat(), if path is a relative path and fd refers to
a valid file descriptor which is not a directory.
ENOSYS
The file system does not support symbolic links.
The readlinkat() function will fail if:
EBADF
The path argument is a relative path and fd
is not a valid, open file descriptor or the special value
AT_FDCWD.
The readlink() function may fail if:
EACCES
Read permission is denied for the directory.
ELOOP
More than {SYMLOOP_MAX} symbolic links were
encountered in resolving path.
ENAMETOOLONG
As a result of encountering a symbolic link in resolution
of the path argument, the length of the substituted pathname string exceeded
{PATH_MAX}.
Portable applications should not assume that the returned contents of the
symbolic link are null-terminated.
See attributes(7) for descriptions of the following attributes:
| ATTRIBUTE
TYPE |
ATTRIBUTE VALUE |
| Interface Stability |
Standard |
| MT-Level |
Async-Signal-Safe |