DOKK / manpages / debian 12 / libexplain-dev / explain_ungetc_or_die.3.en
explain_ungetc_or_die(3) Library Functions Manual explain_ungetc_or_die(3)

explain_ungetc_or_die - push a character back to a stream and report errors

#include <libexplain/ungetc.h>

void explain_ungetc_or_die(int c, FILE *fp);
int explain_ungetc_on_error(int c, FILE *fp);

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

The explain_ungetc_on_error function is used to call the ungetc(3) system call. On failure an explanation will be printed to stderr, obtained from the explain_ungetc(3) function, but still returns to the caller.

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

The explain_ungetc_or_die function only returns on success, see ungetc(3) for more information. On failure, prints an explanation and exits, it does not return.

The explain_ungetc_on_error function always returns the value return by the wrapped ungetc(3) system call.

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

explain_ungetc_or_die(c, fp);

ungetc(3)
push a character back to a stream
explain_ungetc(3)
explain ungetc(3) errors
exit(2)
terminate the calling process

libexplain version 1.4
Copyright (C) 2010 Peter Miller