c8-1 : usage of fork

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#define OK 0
int glob = 6;
char buf[] = "a write to stdout\r\n";
int main(int argc, char *argv[])
{
int var;
pid_t pid;
var = 88;
if (write(STDOUT_FILENO,buf,sizeof(buf-1)) != sizeof(buf)-1){
printf("write error\r\n");
}
printf("before fork\r\n");
if ( (pid = fork()) < 0){
printf("fork error\r\n");
}else if (pid == 0){
glob++;
var++;
}else {
sleep(2);
}
printf("pid = %d,glob = %d var = %d\r\n",getpid(),glob,var);
getchar();
return OK;
}
apue:210
同标准库函数的缓冲有关系。
ubutu@ubutu-desktop:~$ uname -v
#48-Ubuntu SMP Fri Oct 16 14:04:26 UTC 2009
ubutu@ubutu-desktop:~$ gcc -v
Using built-in specs.
Target: i486-linux-gnu
ubutu@ubutu-desktop:~$ gcc -o fork fork.c
ubutu@ubutu-desktop:~$ ./fork
a write to stdout
before fork
pid = 3437,glob = 7 var = 89
pid = 3436,glob = 6 var = 88
ubutu@ubutu-desktop:~$ ./fork  >a.txt
ubutu@ubutu-desktop:~$ cat a.txt
a write to stdout
before fork
pid = 3439,glob = 7 var = 89
before fork