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.\"     @(#)readlink.2	8.1 (Berkeley) 6/4/93
.\"
.Dd June 4, 1993
.Dt READLINK 2
.Os BSD 4.2
.Sh NAME
.Nm readlink ,
.Nm readlinkat ,
.Nm freadlink
.Nd read value of a symbolic link
.Sh SYNOPSIS
.Fd #include <unistd.h>
.Ft  ssize_t
.Fo readlink
.Fa "const char *restrict path"
.Fa "char *restrict buf"
.Fa "size_t bufsize"
.Fc
.Ft ssize_t
.Fo readlinkat
.Fa "int fd" "const char *restrict path" "char *restrict buf" "size_t bufsize"
.Fc
.Ft ssize_t
.Fo freadlink
.Fa "int fd" "char *restrict buf" "size_t bufsize"
.Fc
.Sh DESCRIPTION
.Fn readlink
places the contents of the symbolic link
.Fa path
in the buffer
.Fa buf ,
which has size
.Fa bufsize .
.Nm Readlink
does not append a
.Dv NUL
character to
.Fa buf .
.Pp
The
.Fn readlinkat
system call is equivalent to
.Fn readlink
except in the case where
.Fa path
specifies a relative path.
In this case the symbolic link whose content is read relative to the
directory associated with the file descriptor
.Fa fd
instead of the current working directory.
If
.Fn readlinkat
is passed the special value
.Dv AT_FDCWD
in the
.Fa fd
parameter, the current working directory is used and the behavior is
identical to a call to
.Fn readlink .
The
.Fn freadlink
system call returns the same information about an open symbolic link file referenced by descriptor 
.Fa fd .
.Sh RETURN VALUES
The call returns the count of characters placed in the buffer
if it succeeds, or a -1 if an error occurs, placing the error
code in the global variable
.Va errno .
.Sh ERRORS
.Fn readlink
will fail if:
.Bl -tag -width Er
.\" ===========
.It Bq Er EACCES
Search permission is denied for a component of the path prefix.
.\" ===========
.It Bq Er EFAULT
.Fa Buf
extends outside the process's allocated address space.
.\" ===========
.It Bq Er EINVAL
The named file is not a symbolic link.
.\" ===========
.It Bq Er EIO
An I/O error occurred while reading from the file system.
.\" ===========
.It Bq Er ELOOP
Too many symbolic links are encountered in translating the pathname.
This is taken to be indicative of a looping symbolic link.
.\" ===========
.It Bq Er ENAMETOOLONG
A component of a pathname exceeded 
.Dv {NAME_MAX}
characters, or an entire path name
(possibly expanded by a symbolic link) exceeded 
.Dv {PATH_MAX}
characters.
.\" ===========
.It Bq Er ENOENT
The named file does not exist.
.\" ===========
.It Bq Er ENOTDIR
A component of the path prefix is not a directory.
.El
.Pp
In addition to the errors returned by the
.Fn readlink ,
the
.Fn readlinkat
may fail if:
.Bl -tag -width Er
.It Bq Er EBADF
The
.Fa path
argument does not specify an absolute path and the
.Fa fd
argument is neither
.Dv AT_FDCWD
nor a valid file descriptor open for searching.
.It Bq Er ENOTDIR
The
.Fa path
argument is not an absolute path and
.Fa fd
is neither
.Dv AT_FDCWD
nor a file descriptor associated with a directory.
.El
.Sh LEGACY SYNOPSIS
.Fd #include <unistd.h>
.Pp
.Ft int
.br
.Fo readlink
.Fa "const char *path"
.Fa "char *buf"
.Fa "int bufsize"
.Fc ;
.Pp
The function type and the type of
.Fa bufsize
have changed.
.Sh SEE ALSO
.Xr lstat 2 ,
.Xr stat 2 ,
.Xr symlink 2 ,
.Xr compat 5 ,
.Xr symlink 7
.Sh STANDARDS
The
.Fn readlinkat
system call is expected to conform to POSIX.1-2008 .
.Sh HISTORY
The
.Fn readlink
function call appeared in
.Bx 4.2 .
The
.Fn readlinkat
system call appeared in OS X 10.10.
The
.Fn freadlink
system call appeared in macOS 13.0.