readlinkat(2) - NetBSD Manual Pages

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READLINK(2)               NetBSD System Calls Manual               READLINK(2)

readlink, readlinkat -- read value of a symbolic link
Standard C Library (libc, -lc)
#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);
readlink() places the contents of the symbolic link path in the buffer buf, which has size bufsiz. readlink() does not append a NUL character to buf. readlinkat() works the same way as readlink() except if path is relative. In that case, it is looked up from a directory whose file descriptor was passed as fd. Search permission is required on this directory. fd can be set to AT_FDCWD in order to specify the current directory.
The call returns the count of characters placed in the buffer if it suc- ceeds, or a -1 if an error occurs, placing the error code in the global variable errno.
A typical use is illustrated in the following piece of code which reads the contents of a symbolic link named /symbolic/link and stores them as null-terminated string: #include <limits.h> #include <unistd.h> char buf[PATH_MAX]; ssize_t len; if ((len = readlink("/symbolic/link", buf, sizeof(buf)-1)) == -1) error handling; buf[len] = '\0';
readlink() and readlinkat() will fail if: [EACCES] Search permission is denied for a component of the path prefix. [EFAULT] buf extends outside the process's allocated address space. [EINVAL] The named file is not a symbolic link. [EIO] An I/O error occurred while reading from the file sys- tem. [ELOOP] Too many symbolic links were encountered in translat- ing the pathname. [ENAMETOOLONG] A component of a pathname exceeded {NAME_MAX} charac- ters, or an entire path name exceeded {PATH_MAX} char- acters. [ENOENT] The named file does not exist. [ENOTDIR] A component of the path prefix is not a directory. In addition, readlinkat() will fail if: [EBADF] path does not specify an absolute path and fd is nei- ther AT_FDCWD nor a valid file descriptor open for reading or searching. [ENOTDIR] path is not an absolute path and fd is a file descrip- tor associated with a non-directory file.
lstat(2), stat(2), symlink(2), symlink(7)
The readlink() function conforms to IEEE Std 1003.1-2001 (``POSIX.1''). readlinkat() conforms to IEEE Std 1003.1-2008 (``POSIX.1'').
The readlink() function appeared in 4.2BSD. The type returned was changed from int to ssize_t in NetBSD 2.1. NetBSD 10.99 July 28, 2013 NetBSD 10.99
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