explain_fgets(3)

NAME
explain_fgets - explain fgets(3) errors

SYNOPSIS
#include <libexplain/fgets.h>

const char *explain_fgets(char *data, int data_size, FILE *fp);
const char *explain_errno_fgets(int errnum, char *data, int data_size, FILE *fp);
void explain_message_fgets(char *message, int message_size, char *data, int data_size, FILE *fp);
void explain_message_errno_fgets(char *message, int message_size, int errnum, char *data, int data_size, FILE *fp);

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

  explain_fgets
const char *explain_fgets(char *data, int data_size, FILE *fp);

The explain_fgets function is used to obtain an explanation of an error returned by the fgets(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.

This function is intended to be used in a fashion similar to the following example:
    if (fgets(data, data_size, fp) < 0)
    {
        fprintf(stderr, "%s\n", explain_fgets(data, data_size, fp));
        exit(EXIT_FAILURE);
    }

data
    The original data, exactly as passed to the fgets(3) system call.

data_size
    The original data_size, exactly as passed to the fgets(3) system call.

fp  The original fp, exactly as passed to the fgets(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.

  explain_errno_fgets
const char *explain_errno_fgets(int errnum, char *data, int data_size, FILE *fp);

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

This function is intended to be used in a fashion similar to the following example:
    if (fgets(data, data_size, fp) < 0)
    {
        int err = errno;
        fprintf(stderr, "%s\n", explain_errno_fgets(err, data, data_size, fp));
        exit(EXIT_FAILURE);
    }

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.

data
    The original data, exactly as passed to the fgets(3) system call.

data_size
    The original data_size, exactly as passed to the fgets(3) system call.

fp  The original fp, exactly as passed to the fgets(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.

  explain_message_fgets
void explain_message_fgets(char *message, int message_size, char *data, int data_size, FILE *fp);

The explain_message_fgets function may be used to obtain an explanation of an error returned by the fgets(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.

This function is intended to be used in a fashion similar to the following example:
    if (fgets(data, data_size, fp) < 0)
    {
        char message[3000];
        explain_message_fgets(message, sizeof(message), data, data_size, fp);
        fprintf(stderr, "%s\n", message);
        exit(EXIT_FAILURE);
    }

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.

data
    The original data, exactly as passed to the fgets(3) system call.

data_size
    The original data_size, exactly as passed to the fgets(3) system call.

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

  explain_message_errno_fgets
void explain_message_errno_fgets(char *message, int message_size, int errnum, char *data, int data_size, FILE *fp);

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

This function is intended to be used in a fashion similar to the following example:
    if (fgets(data, data_size, fp) < 0)
    {
        int err = errno;
        char message[3000];
        explain_message_errno_fgets(message, sizeof(message), err,
            data, data_size, fp);
        fprintf(stderr, "%s\n", message);
        exit(EXIT_FAILURE);
    }

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.

data
    The original data, exactly as passed to the fgets(3) system call.

data_size
    The original data_size, exactly as passed to the fgets(3) system call.

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

SEE ALSO

fgets(3)
    input of strings

explain_fgets_or_die(3)
    input of strings and report errors

COPYRIGHT
libexplain version
Copyright (C) 2008 Peter Miller