error.c

#include    <stdio.h>
#include    <errno.h>
#include    <stdlib.h>
#include    <string.h>
#include    <stdarg.h>        /* ANSI C header file */
#include    <syslog.h>        /* for syslog() */

#define     MAXLINE     4096

int        daemon_proc;       /* set nonzero by daemon_init() */

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

/* Nonfatal error related to system call
 * Print message and return */

void err_ret(const char *fmt, ...) {

    va_list        ap;    

    va_start(ap, fmt);    
    err_doit(1, LOG_INFO, fmt, ap);
    va_end(ap);
    return;
}

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

void err_sys(const char *fmt, ...) {

    va_list        ap;

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

/* Fatal error related to system call
 * Print message, dump core, and terminate */

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

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

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

void err_msg(const char *fmt, ...) {

    va_list        ap;

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

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

void err_quit(const char *fmt, ...) {

    va_list        ap;

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

/* Print message and return to caller
 * Caller specifies "errnoflag" and "level" */

static void err_doit(int errnoflag, int level, const char *fmt, va_list ap) {

    int        errno_save, n;
    char    buf[MAXLINE + 1];

    errno_save = errno;                  /* value caller might want printed */
#ifdef    HAVE_VSNPRINTF
    vsnprintf(buf, MAXLINE, fmt, ap);    /* safe */
#else
    vsprintf(buf, fmt, ap);              /* not safe */
#endif
    n = strlen(buf);
    if (errnoflag)
        snprintf(buf + n, MAXLINE - n, ": %s", strerror(errno_save));
    strcat(buf, "\n");

    if (daemon_proc) {
        syslog(level, buf);
    } else {
        fflush(stdout);        /* in case stdout and stderr are the same */
        fputs(buf, stderr);
        fflush(stderr);
    }
    return;
}