#include "apue.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. */voiderr_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. */voiderr_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. */voiderr_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. */voiderr_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. */voiderr_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. */voiderr_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 voiderr_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 */}