输出至标准出错文件的出错处理函数

[root@localhost unix_env_advance_prog]# cat error.c 

#include "apue.h"

#include <errno.h>

#include <stdarg.h>



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 dand terminate.

*/

void 

err_dump(const char *fmt, ...)

{

        va_list ap;



        va_start(ap, fmt);

        err_doit(1, errno, fmt, ap);

        va_end(ap);

        abort();

        exit(1);

}



/*

* 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 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);

        fputs(buf, stderr);

        fflush(NULL);

}