errorlog.c

来自「APUE(第二版)的随书源代码,与第一版的代码相比增加了一些章节的代码(详见第二」· C语言 代码 · 共 100 行

/* Error routines for programs that can run as a daemon. */

#include	<errno.h>		/* for definition of errno */
#include	<stdarg.h>		/* ANSI C header file */
#include	<syslog.h>
#include	"ourhdr.h"

static void	log_doit(int, int, const char *, va_list ap);

extern int	debug;		/* caller must define and set this:
						   nonzero if interactive, zero if daemon */

/* Initialize syslog(), if running as daemon. */

void
log_open(const char *ident, int option, int facility)
{
	if (debug == 0)
		openlog(ident, option, facility);
}

/* Nonfatal error related to a system call.
 * Print a message with the system's errno value and return. */

void
log_ret(const char *fmt, ...)
{
	va_list		ap;

	va_start(ap, fmt);
	log_doit(1, LOG_ERR, fmt, ap);
	va_end(ap);
	return;
}

/* Fatal error related to a system call.
 * Print a message and terminate. */

void
log_sys(const char *fmt, ...)
{
	va_list		ap;

	va_start(ap, fmt);
	log_doit(1, LOG_ERR, fmt, ap);
	va_end(ap);
	exit(2);
}

/* Nonfatal error unrelated to a system call.
 * Print a message and return. */

void
log_msg(const char *fmt, ...)
{
	va_list		ap;

	va_start(ap, fmt);
	log_doit(0, LOG_ERR, fmt, ap);
	va_end(ap);
	return;
}

/* Fatal error unrelated to a system call.
 * Print a message and terminate. */

void
log_quit(const char *fmt, ...)
{
	va_list		ap;

	va_start(ap, fmt);
	log_doit(0, LOG_ERR, fmt, ap);
	va_end(ap);
	exit(2);
}

/* Print a message and return to caller.
 * Caller specifies "errnoflag" and "priority". */

static void
log_doit(int errnoflag, int priority, const char *fmt, va_list ap)
{
	int		errno_save;
	char	buf[MAXLINE];

	errno_save = errno;		/* value caller might want printed */
	vsprintf(buf, fmt, ap);
	if (errnoflag)
		sprintf(buf+strlen(buf), ": %s", strerror(errno_save));
	strcat(buf, "\n");
	if (debug) {
		fflush(stdout);
		fputs(buf, stderr);
		fflush(stderr);
	} else
		syslog(priority, buf);
	return;
}