libexplain/ferror.h File Reference

explain ferror(3) errors More...

#include <libexplain/gcc_attributes.h>
#include <libexplain/large_file_support.h>
#include <stdio.h>

Go to the source code of this file.

Functions
void	explain_ferror_or_die (FILE *fp)
int	explain_ferror_on_error (FILE *fp) LIBEXPLAIN_WARN_UNUSED_RESULT
const char *	explain_ferror (FILE *fp) LIBEXPLAIN_WARN_UNUSED_RESULT
const char *	explain_errno_ferror (int errnum, FILE *fp) LIBEXPLAIN_WARN_UNUSED_RESULT
void	explain_message_ferror (char *message, int message_size, FILE *fp)
void	explain_message_errno_ferror (char *message, int message_size, int errnum, FILE *fp)

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Detailed Description

explain ferror(3) errors

Definition in file ferror.h.

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Function Documentation

const char* explain_errno_ferror	(	int	errnum,
		FILE *	fp
	)

The explain_errno_ferror function is used to obtain an explanation of an error returned by the ferror(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 (ferror(fp) < 0)
 {
     int err = errno;
     fprintf(stderr, "%s\n", explain_errno_ferror(err, fp));
     exit(EXIT_FAILURE);
 }

It is essential that this function cal be placed as close as possible to the I/O code that has caused the problem, otherwise intervening code could have altered the errno global variable.

The above code example is available pre-packaged as the explain_ferror_or_die function.

Parameters:

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 ferror(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.

const char* explain_ferror

(

FILE *

fp

)

The explain_ferror function is used to obtain an explanation of an error returned by the ferror(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 (ferror(fp) < 0)
 {
     fprintf(stderr, "%s\n", explain_ferror(fp));
     exit(EXIT_FAILURE);
 }

It is essential that this function cal be placed as close as possible to the I/O code that has caused the problem, otherwise intervening code could have altered the errno global variable.

The above code example is available pre-packaged as the explain_ferror_or_die function.

Parameters:

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

int explain_ferror_on_error

(

FILE *

fp

)

The explain_ferror_on_error function is used to call the ferror(3) system call. On failure an explanation will be printed to stderr, obtained from the explain_ferror(3) function.

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

 if (explain_ferror_on_error(fp) < 0)
 {
     ...cope with error
     ...no need to print error message
 }

Parameters:

fp	The fp, exactly as to be passed to the ferror(3) system call.

Returns:

The value returned by the wrapped ferror(3) system call.

void explain_ferror_or_die

(

FILE *

fp

)

The explain_ferror_or_die function is used to call the ferror(3) system call. On failure an explanation will be printed to stderr, obtained from the explain_ferror(3) function, and then the process terminates by calling exit(EXIT_FAILURE).

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

 explain_ferror_or_die(fp);

Parameters:

fp	The fp, exactly as to be passed to the ferror(3) system call.

Returns:

This function only returns on success. On failure, prints an explanation and exits, it does not return.

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

The explain_message_errno_ferror function is used to obtain an explanation of an error returned by the ferror(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 (ferror(fp) < 0)
 {
     int err = errno;
     char message[3000];
     explain_message_errno_ferror(message, sizeof(message), err, fp);
     fprintf(stderr, "%s\n", message);
     exit(EXIT_FAILURE);
 }

It is essential that this function cal be placed as close as possible to the I/O code that has caused the problem, otherwise intervening code could have altered the errno global variable.

The above code example is available pre-packaged as the explain_ferror_or_die function.

Parameters:

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 ferror(3) system call.

void explain_message_ferror	(	char *	message,
		int	message_size,
		FILE *	fp
	)

The explain_message_ferror function is used to obtain an explanation of an error returned by the ferror(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.

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

It is essential that this function cal be placed as close as possible to the I/O code that has caused the problem, otherwise intervening code could have altered the errno global variable.

The above code example is available pre-packaged as the explain_ferror_or_die function.

Parameters:

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 ferror(3) system call.