[root@slave bdkyr]# cat fork_test.c
/*
* create by bdkyr
* date 2015-1-22
*/
#include <stdio.h>
#include <errno.h>
#include <unistd.h>
#include <stdarg.h>
#include <string.h>
#define MAXLINE 4096 /* max line length */
int glob = 6;
char buf[]= "a write to stdout\n";
void err_sys(const char *fmt, ...);
static void err_doit(int, int, const char *, va_list);
int main(void){
int var;
pid_t pid;
var = 88;
if (write (STDOUT_FILENO, buf, sizeof(buf) -1) != sizeof(buf)-1)
err_sys("write error");
printf("before fork\n");
if((pid = fork()) < 0){
err_sys("fork error");
}else if(pid == 0){
glob++;
var++;
}else{
sleep(2);
}
printf("pid=%d, glob = %d, var = %d\n", getpid(),glob, var);
exit(0);
}
void err_sys(const char *fmt, ...){
va_list ap;
va_start(ap, fmt);
err_doit(1, errno, fmt, ap);
va_end(ap);
exit(1);
}
static void err_doit(int errnoflag, int error, const char *fmt, va_list ap){
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);
}
[root@slave bdkyr]# gcc fork_test.c -o fork_test
[root@slave bdkyr]# ./fork_test
a write to stdout
before fork
pid=5209, glob = 7, var = 89
pid=5208, glob = 6, var = 88
