[root@slave bdkyr]# cat fork_test.c
/*
* create by bdkyr
* date 2015⑴⑵2
*/
#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 ";
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) ⑴) != sizeof(buf)⑴)
err_sys("write error");
printf("before fork ");
if((pid = fork()) < 0){
err_sys("fork error");
}else if(pid == 0){
glob++;
var++;
}else{
sleep(2);
}
printf("pid=%d,glob = %d,var = %d ",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,ap);
if(errnoflag)
snprintf(buf+strlen(buf),MAXLINE-strlen(buf),": %s",strerror(error));
strcat(buf," ");
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
