// myerr.h

#include <errno.h>/* for definition of errno */
#include <stdarg.h>/* ISO C variable aruments */


static void err_doit(int, int, const char *, va_list);


/*
 * Nonfatal error related to a system call.
 * Print a message and return.
 */
void
err_ret(const char *fmt, ...)
{
va_list ap;


va_start(ap, fmt);
err_doit(1, errno, fmt, ap);
va_end(ap);
}


/*
 * Fatal error related to a system call.
 * Print a message and terminate.
 */
void
err_sys(const char *fmt, ...)
{
va_list ap;


va_start(ap, fmt);
err_doit(1, errno, fmt, ap);
va_end(ap);
exit(1);
}


/*
 * Fatal error unrelated to a system call.
 * Error code passed as explict parameter.
 * Print a message and terminate.
 */
void
err_exit(int error, const char *fmt, ...)
{
va_list ap;


va_start(ap, fmt);
err_doit(1, error, fmt, ap);
va_end(ap);
exit(1);
}


/*
 * Fatal error related to a system call.
 * Print a message, dump core, and terminate.
 */
void
err_dump(const char *fmt, ...)
{
va_list ap;


va_start(ap, fmt);
err_doit(1, errno, fmt, ap);
va_end(ap);
abort(); /* dump core and terminate */
exit(1); /* shouldn't get here */
}


/*
 * Nonfatal error unrelated to a system call.
 * Print a message and return.
 */
void
err_msg(const char *fmt, ...)
{
va_list ap;


va_start(ap, fmt);
err_doit(0, 0, fmt, ap);
va_end(ap);
}


/*
 * Fatal error unrelated to a system call.
 * Print a message and terminate.
 */
void
err_quit(const char *fmt, ...)
{
va_list ap;


va_start(ap, fmt);
err_doit(0, 0, fmt, ap);
va_end(ap);
exit(1);
}


/*
 * Print a message and return to caller.
 * Caller specifies "errnoflag".
 */
static void
err_doit(int errnoflag, int error, const char *fmt, va_list ap)
{
    char buf[MAXLINE];
    vsnprintf(buf, MAXLINE, fmt, ap);
    if (errnoflag)
        snprintf(buf+strlen(buf), MAXLINE-strlen(buf), ": %s", strerror(error));
    strcat(buf, "\n");
    fflush(stdout);/* in case stdout and stderr are the same */
    fputs(buf, stderr);
    fflush(NULL); /* flushes all stdio output streams */
}