printf in Linux does not work right

Question

pid_t pid=fork();
printf("%d\n",pid);
if(pid==0){
     sleep(3);
     printf("!");
}
else  
{   
   printf("@");
   read_routine(clnt_sock,buf);
}

On my console, I can see two pid and !, but there is no @.

And when I delete the statement read_routine(clnt_sock,buf);, then I can see @ on console.

In read_routine function, there is just some input statement using fgets().

Are there some secrets of printf?

There some secrets of stdout. Line-buffering is one of them. — Martin James, Feb 22 '16 at 15:43
Dupe to http://stackoverflow.com/q/13035075/694576 and and and? — alk, Feb 22 '16 at 15:43

score 3 · Answer 1 · answered Feb 22 '16 at 15:40

3

Your output is probably buffered. After the printf, you will likely want to fflush(stdout);.

answered Feb 22 '16 at 15:40

Toby Speight

score 2 · Answer 2 · answered Feb 22 '16 at 15:40

2

Add fflush(stdout) after print and try.

answered Feb 22 '16 at 15:40

user2026753

2 Answers2