.\"
.\" 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_fclose
.cp 0  \" Solaris defaults to ''.cp 1'', sheesh.
.TH explain_fclose 3
.SH NAME
explain_fclose \- explain fclose(3) errors
.if require_index \{
.XX "explain_fclose(3)" "explain fclose(3) errors"
.\}
.SH SYNOPSIS
#include <libexplain/fclose.h>
.br
const char *explain_fclose(FILE *fp);
.br
const char *explain_errno_fclose(int errnum, FILE *fp);
.br
void explain_message_fclose(char *message, int message_size, FILE *fp);
.br
void explain_message_errno_fclose(char *message, int message_size,
int errnum, FILE *fp);
.SH DESCRIPTION
These functions may be used to obtain explanations of
\f[I]fclose\fP(3) errors.
.\" ------------------------------------------------------------------------
.SS explain_fclose
const char *explain_fclose(FILE * fp);
.PP
The explain_fclose function is used to obtain an explanation of an
error returned by the \f[I]fclose\fP(3) function.  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
if (fclose(fp))
{
    fprintf(stderr, "%s\en", explain_fclose(fp));
    exit(EXIT_FAILURE);
}
.fi
.ft R
.RE
.TP 8n
\f[I]fp\fP
The original fp, exactly as passed to the \f[I]fclose\fP(3) 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.
.PP
\f[B]Note:\fP
This function may be of little diagnostic value, because libc may have
destroyed any useful context, leaving nothing for libexplain to work
with (this is true of glibc in particular).  For files that are open
for writing, you will obtain more useful information by first calling
\f[I]fflush\fP(3), as in the following example
.RS
.ft CW
.nf
if (fflush(fp))
{
    fprintf(stderr, "%s\en", explain_fflush(fp));
    exit(EXIT_FAILURE);
}
if (fclose(fp))
{
    fprintf(stderr, "%s\en", explain_fclose(fp));
    exit(EXIT_FAILURE);
}
.fi
.ft R
.RE
.\" ------------------------------------------------------------------------
.SS explain_errno_fclose
const char *explain_errno_fclose(int errnum, FILE * fp);
.PP
The explain_errno_fclose function is used to obtain an explanation
of an error returned by the \f[I]fclose\fP(3) function.  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
if (fclose(fp))
{
    int err = errno;
    fprintf(stderr, "%s\en", explain_errno_fclose(err, fp));
    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]fp\fP
The original fp, exactly as passed to the \f[I]fclose\fP(3) 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.
.PP
\f[B]Note:\fP
This function may be of little diagnostic value, because libc may have
destroyed any useful context, leaving nothing for libexplain to work
with (this is true of glibc in particular).  For files that are open
for writing, you will obtain more useful information by first calling
\f[I]fflush\fP(3), as in the following example
.RS
.ft CW
.nf
if (fflush(fp))
{
    int err = errno;
    fprintf(stderr, "%s\en", explain_errno_fflush(err, fp));
    exit(EXIT_FAILURE);
}
if (fclose(fp))
{
    int err = errno;
    fprintf(stderr, "%s\en", explain_errno_fclose(err, fp));
    exit(EXIT_FAILURE);
}
.fi
.ft R
.RE
.\" ------------------------------------------------------------------------
.SS explain_message_fclose
void explain_message_fclose(char *message, int message_size, FILE *fp);
.PP
The explain_message_fclose function is used to obtain an explanation
of an error returned by the \f[I]fclose\fP(3) function.  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
if (fclose(fp))
{
    char message[3000];
    explain_message_fclose(message, sizeof(message), fp);
    fprintf(stderr, "%s\en", 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]fp\fP
The original fp, exactly as passed to the \f[I]fclose(3)\fP system call.
.PP
\f[B]Note:\fP
This function may be of little diagnostic value, because libc may have
destroyed any useful context, leaving nothing for libexplain to work
with (this is true of glibc in particular).  For files that are open
for writing, you will obtain more useful information by first calling
\f[I]fflush\fP(3), as in the following example
.RS
.ft CW
.nf
if (fflush(fp))
{
    char message[3000];
    explain_message_fflush(message, sizeof(message), fp);
    fprintf(stderr, "%s\en", message);
    exit(EXIT_FAILURE);
}
if (fclose(fp))
{
    char message[3000];
    explain_message_fclose(message, sizeof(message), fp);
    fprintf(stderr, "%s\en", message);
    exit(EXIT_FAILURE);
}
.fi
.ft R
.RE
.\" ------------------------------------------------------------------------
.SS explain_message_errno_fclose
void explain_message_errno_fclose(char *message, int message_size,
int errnum, FILE *fp);
.PP
The explain_message_errno_fclose function is used to obtain
an explanation of an error returned by the \f[I]fclose\fP(3)
function.  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
if (fclose(fp))
{
    int err = errno;
    char message[3000];
    explain_message_errno_fclose(message, sizeof(message),
        err, fp);
    fprintf(stderr, "%s\en", 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]fp\fP
The original fp, exactly as passed to the \f[I]fclose\fP(3) system call.
.PP
\f[B]Note:\fP
This function may be of little diagnostic value, because libc may have
destroyed any useful context, leaving nothing for libexplain to work
with (this is true of glibc in particular).  For files that are open
for writing, you will obtain more useful information by first calling
\f[I]fflush\fP(3), as in the following example
.RS
.ft CW
.nf
if (fflush(fp))
{
    int err = errno;
    char message[3000];
    explain_message_errno_fflush(message, sizeof(message),
        err, fp);
    fprintf(stderr, "%s\en", message);
    exit(EXIT_FAILURE);
}
if (fclose(fp))
{
    int err = errno;
    char message[3000];
    explain_message_errno_fclose(message, sizeof(message),
        err, fp);
    fprintf(stderr, "%s\en", message);
    exit(EXIT_FAILURE);
}
.fi
.ft R
.RE
.\" ------------------------------------------------------------------------
.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>