libexplain/fgets.h File Reference

explain fgets(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
char *	explain_fgets_or_die (char *data, int data_size, FILE *fp)
char *	explain_fgets_on_error (char *data, int data_size, FILE *fp) LIBEXPLAIN_WARN_UNUSED_RESULT
const char *	explain_fgets (char *data, int data_size, FILE *fp) LIBEXPLAIN_WARN_UNUSED_RESULT
const char *	explain_errno_fgets (int errnum, char *data, int data_size, FILE *fp) LIBEXPLAIN_WARN_UNUSED_RESULT
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)

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Detailed Description

explain fgets(3) errors

Definition in file fgets.h.

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Function Documentation

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);
 }

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

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);
 }

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

Parameters:

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.

char* explain_fgets_on_error	(	char *	data,
		int	data_size,
		FILE *	fp
	)

The explain_fgets_on_error function is used to call the fgets(3) system call. On failure an explanation will be printed to stderr, obtained from the explain_fgets(3) function.

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

 if (explain_fgets_on_error(data, data_size, fp) < 0)
 {
     ...cope with error
     ...no need to print error message
 }

Parameters:

data	The data, exactly as to be passed to the fgets(3) system call.
data_size	The data_size, exactly as to be passed to the fgets(3) system call.
fp	The fp, exactly as to be passed to the fgets(3) system call.

Returns:

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

char* explain_fgets_or_die	(	char *	data,
		int	data_size,
		FILE *	fp
	)

The explain_fgets_or_die function is used to call the fgets(3) system call. On failure an explanation will be printed to stderr, obtained from the explain_fgets(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_fgets_or_die(data, data_size, fp);

Parameters:

data	The data, exactly as to be passed to the fgets(3) system call.
data_size	The data_size, exactly as to be passed to the fgets(3) system call.
fp	The fp, exactly as to be passed to the fgets(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_fgets	(	char *	message,
		int	message_size,
		int	errnum,
		char *	data,
		int	data_size,
		FILE *	fp
	)

The explain_message_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;
     char message[3000];
     explain_message_errno_fgets(message, sizeof(message), err, data,
         data_size, fp);
     fprintf(stderr, "%s\n", message);
     exit(EXIT_FAILURE);
 }

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

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

The explain_message_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.

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);
 }

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