.\" Copyright (c) 2001-2003 The Open Group, All Rights Reserved 
.TH "READLINK" 3P 2003 "IEEE/The Open Group" "POSIX Programmer's Manual"
.\" readlink 
.SH PROLOG
This manual page is part of the POSIX Programmer's Manual.
The Linux implementation of this interface may differ (consult
the corresponding Linux manual page for details of Linux behavior),
or the interface may not be implemented on Linux.
.SH NAME
readlink \- read the contents of a symbolic link
.SH SYNOPSIS
.LP
\fB#include <unistd.h>
.br
.sp
ssize_t readlink(const char *restrict\fP \fIpath\fP\fB, char *restrict\fP
\fIbuf\fP\fB,
.br
\ \ \ \ \ \  size_t\fP \fIbufsize\fP\fB);
.br
\fP
.SH DESCRIPTION
.LP
The \fIreadlink\fP() function shall place the contents of the symbolic
link referred to by \fIpath\fP in the buffer \fIbuf\fP
which has size \fIbufsize\fP. If the number of bytes in the symbolic
link is less than \fIbufsize\fP, the contents of the
remainder of \fIbuf\fP are unspecified. If the \fIbuf\fP argument
is not large enough to contain the link content, the first
\fIbufsize\fP bytes shall be placed in \fIbuf\fP.
.LP
If the value of \fIbufsize\fP is greater than {SSIZE_MAX}, the result
is implementation-defined.
.SH RETURN VALUE
.LP
Upon successful completion, \fIreadlink\fP() shall return the count
of bytes placed in the buffer. Otherwise, it shall return a
value of -1, leave the buffer unchanged, and set \fIerrno\fP to indicate
the error.
.SH ERRORS
.LP
The \fIreadlink\fP() function shall fail if:
.TP 7
.B EACCES
Search permission is denied for a component of the path prefix of
\fIpath\fP.
.TP 7
.B EINVAL
The \fIpath\fP argument names a file that is not a symbolic link.
.TP 7
.B EIO
An I/O error occurred while reading from the file system.
.TP 7
.B ELOOP
A loop exists in symbolic links encountered during resolution of the
\fIpath\fP argument.
.TP 7
.B ENAMETOOLONG
The length of the \fIpath\fP argument exceeds {PATH_MAX} or a pathname
component is longer than {NAME_MAX}.
.TP 7
.B ENOENT
A component of \fIpath\fP does not name an existing file or \fIpath\fP
is an empty string.
.TP 7
.B ENOTDIR
A component of the path prefix is not a directory.
.sp
.LP
The \fIreadlink\fP() function may fail if:
.TP 7
.B EACCES
Read permission is denied for the directory.
.TP 7
.B ELOOP
More than {SYMLOOP_MAX} symbolic links were encountered during resolution
of the \fIpath\fP argument.
.TP 7
.B ENAMETOOLONG
As a result of encountering a symbolic link in resolution of the \fIpath\fP
argument, the length of the substituted pathname
string exceeded {PATH_MAX}.
.sp
.LP
\fIThe following sections are informative.\fP
.SH EXAMPLES
.SS Reading the Name of a Symbolic Link
.LP
The following example shows how to read the name of a symbolic link
named \fB/modules/pass1\fP.
.sp
.RS
.nf

\fB#include <unistd.h>
.sp

char buf[1024];
ssizet_t len;
\&...
if ((len = readlink("/modules/pass1", buf, sizeof(buf)-1)) != -1)
    buf[len] = '\\0';
\fP
.fi
.RE
.SH APPLICATION USAGE
.LP
Conforming applications should not assume that the returned contents
of the symbolic link are null-terminated.
.SH RATIONALE
.LP
Since IEEE\ Std\ 1003.1-2001 does not require any association of file
times with symbolic links, there is no requirement
that file times be updated by \fIreadlink\fP(). The type associated
with \fIbufsiz\fP is a \fBsize_t\fP in order to be
consistent with both the ISO\ C standard and the definition of \fIread\fP().
The behavior
specified for \fIreadlink\fP() when \fIbufsiz\fP is zero represents
historical practice. For this case, the standard developers
considered a change whereby \fIreadlink\fP() would return the number
of non-null bytes contained in the symbolic link with the
buffer \fIbuf\fP remaining unchanged; however, since the \fBstat\fP
structure member \fIst_size\fP value can be used to
determine the size of buffer necessary to contain the contents of
the symbolic link as returned by \fIreadlink\fP(), this proposal
was rejected, and the historical practice retained.
.SH FUTURE DIRECTIONS
.LP
None.
.SH SEE ALSO
.LP
\fIlstat\fP(), \fIstat\fP(), \fIsymlink\fP(),
the Base Definitions volume of IEEE\ Std\ 1003.1-2001, \fI<unistd.h>\fP
.SH COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
Electrical and Electronics Engineers, Inc and The Open Group. In the
event of any discrepancy between this version and the original IEEE and
The Open Group Standard, the original IEEE and The Open Group Standard
is the referee document. The original Standard can be obtained online at
http://www.opengroup.org/unix/online.html .