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explain_fgetpos

explain_fgetpos

Section: C Library Functions (3)
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NAME

explain_fgetpos - explain fgetpos(3) errors  

SYNOPSIS

#include <libexplain/fgetpos.h>

const char *explain_fgetpos(FILE *fp, fpos_t *pos);
const char *explain_errno_fgetpos(int errnum, FILE *fp, fpos_t *pos);
void explain_message_fgetpos(char *message, int message_size, FILE *fp, fpos_t *pos);
void explain_message_errno_fgetpos(char *message, int message_size, int errnum, FILE *fp, fpos_t *pos);  

DESCRIPTION

These functions may be used to obtain explanations for errors returned by the fgetpos(3) system call.  

explain_fgetpos

const char *explain_fgetpos(FILE *fp, fpos_t *pos);

The explain_fgetpos function is used to obtain an explanation of an error returned by the fgetpos(3) system call. The least the message will contain is the value of strerror(errno), but usually it will do much better, and indicate the underlying cause in more detail.

The errno global variable will be used to obtain the error value to be decoded.

fp
The original fp, exactly as passed to the fgetpos(3) system call.
pos
The original pos, exactly as passed to the fgetpos(3) system call.
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.

Note: This function is not thread safe, because it shares a return buffer across all threads, and many other functions in this library.

Example: This function is intended to be used in a fashion similar to the following example:

if (fgetpos(fp, pos) < 0)
{
fprintf(stderr, "%s\n", explain_fgetpos(fp, pos));
    exit(EXIT_FAILURE);
}

The above code example is available pre-packaged as the explain_fgetpos_or_die(3) function.  

explain_errno_fgetpos

const char *explain_errno_fgetpos(int errnum, FILE *fp, fpos_t *pos);

The explain_errno_fgetpos function is used to obtain an explanation of an error returned by the fgetpos(3) system call. The least the message will contain is the value of strerror(errno), but usually it will do much better, and indicate the underlying cause in more detail.

errnum
The error value to be decoded, usually obtained from the errno global variable just before this function is called. This is necessary if you need to call any code between the system call to be explained and this function, because many libc functions will alter the value of errno.
fp
The original fp, exactly as passed to the fgetpos(3) system call.
pos
The original pos, exactly as passed to the fgetpos(3) system call.
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.

Note: This function is not thread safe, because it shares a return buffer across all threads, and many other functions in this library.

Example: This function is intended to be used in a fashion similar to the following example:

if (fgetpos(fp, pos) < 0)
{
    int err = errno;
fprintf(stderr, "%s\n", explain_errno_fgetpos(err, fp, pos));
    exit(EXIT_FAILURE);
}

The above code example is available pre-packaged as the explain_fgetpos_or_die(3) function.  

explain_message_fgetpos

void explain_message_fgetpos(char *message, int message_size, FILE *fp, fpos_t *pos);

The explain_message_fgetpos function is used to obtain an explanation of an error returned by the fgetpos(3) system call. The least the message will contain is the value of strerror(errno), but usually it will do much better, and indicate the underlying cause in more detail.

The errno global variable will be used to obtain the error value to be decoded.

message
The location in which to store the returned message. If a suitable message return buffer is supplied, this function is thread safe.
message_size
The size in bytes of the location in which to store the returned message.
fp
The original fp, exactly as passed to the fgetpos(3) system call.
pos
The original pos, exactly as passed to the fgetpos(3) system call.

Example: This function is intended to be used in a fashion similar to the following example:

if (fgetpos(fp, pos) < 0)
{
    char message[3000];
explain_message_fgetpos(message, sizeof(message), fp, pos);
    fprintf(stderr, "%s\n", message);
    exit(EXIT_FAILURE);
}

The above code example is available pre-packaged as the explain_fgetpos_or_die(3) function.  

explain_message_errno_fgetpos

void explain_message_errno_fgetpos(char *message, int message_size, int errnum, FILE *fp, fpos_t *pos);

The explain_message_errno_fgetpos function is used to obtain an explanation of an error returned by the fgetpos(3) system call. The least the message will contain is the value of strerror(errno), but usually it will do much better, and indicate the underlying cause in more detail.

message
The location in which to store the returned message. If a suitable message return buffer is supplied, this function is thread safe.
message_size
The size in bytes of the location in which to store the returned message.
errnum
The error value to be decoded, usually obtained from the errno global variable just before this function is called. This is necessary if you need to call any code between the system call to be explained and this function, because many libc functions will alter the value of errno.
fp
The original fp, exactly as passed to the fgetpos(3) system call.
pos
The original pos, exactly as passed to the fgetpos(3) system call.

Example: This function is intended to be used in a fashion similar to the following example:

if (fgetpos(fp, pos) < 0)
{
    int err = errno;
    char message[3000];
explain_message_errno_fgetpos(message, sizeof(message), err, fp, pos);
    fprintf(stderr, "%s\n", message);
    exit(EXIT_FAILURE);
}

The above code example is available pre-packaged as the explain_fgetpos_or_die(3) function.  

SEE ALSO

fgetpos(3)
reposition a stream
explain_fgetpos_or_die(3)
reposition a stream and report errors
 

COPYRIGHT

libexplain version 0.37
Copyright (C) 2010 Peter Miller


 

Index

NAME
SYNOPSIS
DESCRIPTION
explain_fgetpos
explain_errno_fgetpos
explain_message_fgetpos
explain_message_errno_fgetpos
SEE ALSO
COPYRIGHT

This document was created by man2html, using the manual pages.
Time: 21:45:48 GMT, April 16, 2011