What does this line do ?
while (wait(NULL)== -1);
This line is written inside a parent process after fork.
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3See the [man page for wait](http://man7.org/linux/man-pages/man2/wait.2.html). – Paul R Apr 12 '18 at 15:06
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1This loop will keep the parent process from exiting until `wait` function returns a valid `pid`. – Sergey Kalinichenko Apr 12 '18 at 15:09
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1When you have a function that you don't understand, either type "man func" if you are on linux, or "msdn func" if you are on windows. For C function, the man page is suffisant. – Tom's Apr 12 '18 at 15:09
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@Tom's "sufficient"? – user202729 Apr 12 '18 at 15:14
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@user202729 Yes, "sufficient". "suffisant" is the french word ... I make a mistake. – Tom's Apr 12 '18 at 15:17
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EDIT: I stand corrected! Thanks @interjay
From the wait man page:
wait() and waitpid() The wait() system call suspends execution of the calling process until one of its children terminates. The call wait(&status) is equivalent to: waitpid(-1, &status, 0)
From wait man page
wait(): on success, returns the process ID of the terminated child; on error, -1 is returned.
So what the code is doing here is waiting for any child process to terminate with an error, and we are ignoring the return value. (passing in a NULL ptr instead of a ptr to an int which the return value would be stored in).
Carson Harmon
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You quoted the wrong bit about the return value of `-1`. What it actually means is that there was an error. What you quoted is about the parameter to `waitpid`. – interjay Apr 12 '18 at 19:41
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