.\"
.\" libexplain - Explain errno values returned by libc functions
.\" Copyright (C) 2008, 2009, 2011 Peter Miller
.\" Written by Peter Miller <pmiller@opensource.org.au>
.\"
.\" This program is free software; you can redistribute it and/or modify
.\" it under the terms of the GNU General Public License as published by
.\" the Free Software Foundation; either version 3 of the License, or
.\" (at your option) any later version.
.\"
.\" This program is distributed in the hope that it will be useful,
.\" but WITHOUT ANY WARRANTY; without even the implied warranty of
.\" MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
.\" General Public License for more details.
.\"
.\" You should have received a copy of the GNU General Public License
.\" along with this program. If not, see <http://www.gnu.org/licenses/>.
.\"
.ds n) explain_access
.cp 0  \" Solaris defaults to ''.cp 1'', sheesh.
.TH explain_access 3
.SH NAME
explain_access \- explain access(2) errors
.if require_index \{
.XX "explain_access(3)" "explain access(2) errors"
.\}
.SH SYNOPSIS
#include <libexplain/access.h>
.br
const char *explain_access(const char *pathname, int mode);
.br
const char *explain_errno_access(int errnum, const char *pathname, int mode);
.br
void explain_message_access(char *message, int message_size,
const char *pathname, int mode);
.br
void explain_message_errno_access(char *message, int message_size,
int errnum, const char *pathname, int mode);
.SH DESCRIPTION
These functions may be used to obtain explanations
for \f[I]access\fP(2) errors.
.\" ------------------------------------------------------------------------
.SS explain_access
const char *explain_access(const char *pathname, int mode);
.PP
The explain_access function is used to obtain an explanation of an
error returned by the \f[I]access\fP(2) system call.  The least the
message will contain is the value of \f[CW]strerror(errno)\fP, but
usually it will do much better, and indicate the underlying cause in
more detail.
.PP
The \f[I]errno\fP global variable will be used to obtain the error value to
be decoded.
.PP
This function is intended to be used in a fashion similar to the
following example:
.RS
.ft CW
.nf
int fd = access(pathname, mode);
if (fd < 0)
{
    fprintf(stderr, "%s\n", explain_access(pathname, mode));
    exit(EXIT_FAILURE);
}
.fi
.ft R
.RE
.TP 8n
\f[I]pathname\fP
The original pathname, exactly as passed to the \f[I]access\fP(2) system call.
.TP 8n
\f[I]mode\fP
The original mode, exactly as passed to the \f[I]access\fP(2) system call.
TP 8n
Returns:
The message explaining the error.  This message buffer is shared
by all libexplain functions which do not supply a buffer in
their argument list.  This will be overwritten by the next call
to any libexplain function which shares this buffer, including
other threads.
.PP
\f[B]Note:\fP
This function is \f[B]not\fP thread safe, because it shares a
return buffer across all threads, and many other functions in
this library.
.\" ------------------------------------------------------------------------
.SS explain_errno_access
const char *explain_errno_access(int errnum, const char *pathname, int mode);
.PP
The explain_errno_access function is used to obtain an explanation
of an error returned by the \f[I]access\fP(2) system call.  The least
the message will contain is the value of \f[CW]strerror(errnum)\fP, but
usually it will do much better, and indicate the underlying cause in
more detail.
.PP
This function is intended to be used in a fashion similar to the
following example:
.RS
.ft CW
.nf
int fd = access(pathname, mode);
if (fd < 0)
{
    int err = errno;
    fprintf(stderr, "%s\n", explain_errno_access(err, pathname,
        mode));
    exit(EXIT_FAILURE);
}
.fi
.ft R
.RE
.TP 8n
\f[I]errnum\fP
The error value to be decoded, usually obtained from the \f[I]errno\fP
global variable just before this function is called.  This is necessary
if you need to call \f[B]any\fP code between the system call to be
explained and this function, because many libc functions will alter the
value of \f[I]errno\fP.
.TP 8n
\f[I]pathname\fP
The original pathname, exactly as passed to the \f[I]access\fP(2) system call.
.TP 8n
\f[I]mode\fP
The original mode, exactly as passed to the \f[I]access\fP(2) system call.
.TP 8n
Returns:
The message explaining the error.  This message buffer is shared
by all libexplain functions which do not supply a buffer in
their argument list.  This will be overwritten by the next call
to any libexplain function which shares this buffer, including
other threads.
.PP
\f[B]Note:\fP
This function is \f[B]not\fP thread safe, because it shares a
return buffer across all threads, and many other functions in
this library.
.\" ------------------------------------------------------------------------
.SS explain_message_access
void explain_message_access(char *message, int message_size,
const char *pathname, int mode);
.PP
The explain_message_access function is used to obtain an
explanation of an error returned by the \f[I]access\fP(2) system call.  The
least the message will contain is the value of \f[CW]strerror(errno)\fP, but
usually it will do much better, and indicate the underlying cause in
more detail.
.PP
The \f[I]errno\fP global variable will be used to obtain the error value to
be decoded.
.PP
This function is intended to be used in a fashion similar to the
following example:
.RS
.ft CW
.nf
int fd = access(pathname, mode);
if (fd < 0)
{
    char message[3000];
    explain_message_access(message, sizeof(message), pathname,
        mode);
    fprintf(stderr, "%s\n", message);
    exit(EXIT_FAILURE);
}
.fi
.ft R
.RE
.TP 8n
\f[I]message\fP
The location in which to store the returned message.  Because
a message return buffer has been supplied, this function is
thread safe.
.TP 8n
\f[I]message_size\fP
The size in bytes of the location in which to store the returned
message.
.TP 8n
\f[I]pathname\fP
The original pathname, exactly as passed to the \f[I]access\fP(2) system call.
.TP 8n
\f[I]mode\fP
The original mode, exactly as passed to the \f[I]access\fP(2) system call.
.\" ------------------------------------------------------------------------
.SS explain_message_errno_access
void explain_message_errno_access(char *message, int message_size,
int errnum, const char *pathname, int mode);
.PP
The explain_message_errno_access function is used to obtain
an explanation of an error returned by the \f[I]access\fP(2)
system call.  The least the message will contain is the value of
\f[CW]strerror(errnum)\fP, but usually it will do much better, and
indicate the underlying cause in more detail.
.PP
This function is intended to be used in a fashion similar to the
following exameple:
.RS
.ft CW
.nf
int fd = access(pathname, mode);
if (fd < 0)
{
    int err = errno;
    char message[3000];
    explain_message_errno_access(message, sizeof(message), err,
        pathname, mode);
    fprintf(stderr, "%s\n", message);
    exit(EXIT_FAILURE);
}
.fi
.ft R
.RE
.TP 8n
\f[I]message\fP
The location in which to store the returned message.  Because
a message return buffer has been supplied, this function is
thread safe.
.TP 8n
\f[I]message_size\fP
The size in bytes of the location in which to store the returned
message.
.TP 8n
\f[I]errnum\fP
The error value to be decoded, usually obtained from the \f[I]errno\fP
global variable just before this function is called.  This is necessary
if you need to call \f[B]any\fP code between the system call to be
explained and this function, because many libc functions will alter the
value of \f[I]errno\fP.
.TP 8n
\f[I]pathname\fP
The original pathname, exactly as passed to the \f[I]access\fP(2) system call.
.TP 8n
\f[I]mode\fP
The original mode, exactly as passed to the \f[I]access\fP(2) system call.
.\" ------------------------------------------------------------------------
.SH COPYRIGHT
.so etc/version.so
.if n .ds C) (C)
.if t .ds C) \(co
libexplain version \*(v)
.br
Copyright \*(C) 2008 Peter Miller
.SH AUTHOR
Written by Peter Miller <pmiller@opensource.org.au>