explain_fclose(3)

NAME
explain_fclose - explain fclose(3) errors

SYNOPSIS
#include <libexplain/fclose.h>
const char *explain_fclose(FILE *fp);
const char *explain_errno_fclose(int errnum, FILE *fp);
void explain_message_fclose(char *message, int message_size, FILE *fp);
void explain_message_errno_fclose(char *message, int message_size, int errnum, FILE *fp);

DESCRIPTION
These functions may be used to obtain explanations of fclose(3) errors.

  explain_fclose
const char *explain_fclose(FILE * fp);

The explain_fclose function is used to obtain an explanation of an error returned by the fclose(3) function. 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 (fclose(fp))
    {
        fprintf(stderr, "%s\n", explain_fclose(fp));
        exit(EXIT_FAILURE);
    }

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

Note: 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 fflush(3), as in the following example
    if (fflush(fp))
    {
        fprintf(stderr, "%s\n", explain_fflush(fp));
        exit(EXIT_FAILURE);
    }
    if (fclose(fp))
    {
        fprintf(stderr, "%s\n", explain_fclose(fp));
        exit(EXIT_FAILURE);
    }

  explain_errno_fclose
const char *explain_errno_fclose(int errnum, FILE * fp);

The explain_errno_fclose function is used to obtain an explanation of an error returned by the fclose(3) function. 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 (fclose(fp))
    {
        int err = errno;
        fprintf(stderr, "%s\n", explain_errno_fclose(err, 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.

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

Note: 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 fflush(3), as in the following example
    if (fflush(fp))
    {
        int err = errno;
        fprintf(stderr, "%s\n", explain_errno_fflush(err, fp));
        exit(EXIT_FAILURE);
    }
    if (fclose(fp))
    {
        int err = errno;
        fprintf(stderr, "%s\n", explain_errno_fclose(err, fp));
        exit(EXIT_FAILURE);
    }

  explain_message_fclose
void explain_message_fclose(char *message, int message_size, FILE *fp);

The explain_message_fclose function is used to obtain an explanation of an error returned by the fclose(3) function. 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 (fclose(fp))
    {
        char message[3000];
        explain_message_fclose(message, sizeof(message), fp);
        fprintf(stderr, "%s\n", message);
        exit(EXIT_FAILURE);
    }

message
    The location in which to store the returned message. Because a message return buffer has been 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 fclose(3) system call.

Note: 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 fflush(3), as in the following example
    if (fflush(fp))
    {
        char message[3000];
        explain_message_fflush(message, sizeof(message), fp);
        fprintf(stderr, "%s\n", message);
        exit(EXIT_FAILURE);
    }
    if (fclose(fp))
    {
        char message[3000];
        explain_message_fclose(message, sizeof(message), fp);
        fprintf(stderr, "%s\n", message);
        exit(EXIT_FAILURE);
    }

  explain_message_errno_fclose
void explain_message_errno_fclose(char *message, int message_size, int errnum, FILE *fp);

The explain_message_errno_fclose function is used to obtain an explanation of an error returned by the fclose(3) function. 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 exameple:
    if (fclose(fp))
    {
        int err = errno;
        char message[3000];
        explain_message_errno_fclose(message, sizeof(message),
            err, fp);
        fprintf(stderr, "%s\n", message);
        exit(EXIT_FAILURE);
    }

message
    The location in which to store the returned message. Because a message return buffer has been 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 fclose(3) system call.

Note: 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 fflush(3), as in the following example
    if (fflush(fp))
    {
        int err = errno;
        char message[3000];
        explain_message_errno_fflush(message, sizeof(message),
            err, fp);
        fprintf(stderr, "%s\n", 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\n", message);
        exit(EXIT_FAILURE);
    }

COPYRIGHT
libexplain version
Copyright (C) 2008 Peter Miller

AUTHOR
Written by Peter Miller <pmiller@opensource.org.au>