APUE函数笔记: 附录

附录:

#include <stdio.h>
#include <errno.h>
#include <string.h>
#include <stdlib.h>
#include <stdarg.h>
#include <syslog.h>

#define MAXLINE  4096  /* max line length */


/*
 * default file access permissions for new files
 */
#define FILE_MODE  (S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH)

/*
 * default permissions for new directories
 */
#define DIR_MODE   (FILE_MODE | S_IXUSR | S_IXGRP | S_IXOTH)


/*
 * print a message and return to caller
 * caller specifies "errnoflag"
 */
void 
err_doit(int errnoflag, int error, const char * fmt, va_list ap)
{
    int   len;
    char  buf[MAXLINE];

    vsnprintf(buf, MAXLINE, fmt, ap);
    if (errnoflag) {
        len = strlen(buf);
        snprintf(buf + len, MAXLINE - len, ": %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 */
}

/*
 * 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);
}


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

/*
 * print a message and return to caller
 * caller specifies "errnoflag" and "priority"
 */
void 
log_doit(int errnoflag, int priority, const char * fmt, va_list ap)
{
    int   len;
    int   errno_save;
    char  buf[MAXLINE];

    errno_save = errno;  /* value caller might want printed */
    vsnprintf(buf, MAXLINE, fmt, ap);
    if (errnoflag) {
        len = strlen(buf);
        snprintf(buf + len, MAXLINE - len, ": %s", strerror(errno_save));
    }
    strcat(buf, "\n");
    if (log_to_stderr) {
        fflush(stdout);
        fputs(buf, stderr);
        fflush(stderr);
    }
    else {
        syslog(priority, "%s", buf);
    }
}

/*
 * initialize syslog(), if running as daemon
 */
void 
log_open(const char * ident, int option, int facility)
{
    if (log_to_stderr == 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);
}

/*
 * 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);
}

/*
 * 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);
}