libexplain/message/errno/ungetc.c File Reference

#include <libexplain/ac/stdio.h>
#include <libexplain/buffer/errno/ungetc.h>
#include <libexplain/ungetc.h>

Go to the source code of this file.

Functions
void	explain_message_errno_ungetc (char *message, int message_size, int errnum, int c, FILE *fp)

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Function Documentation

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

The explain_message_errno_ungetc function is used to obtain an explanation of an error returned by the ungetc(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.

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

Example:

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

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

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

Definition at line 26 of file ungetc.c.