CODEWITHSUNDEEP
linuxfork
MK.
MK.

Reputation: 4027

making parent process wait till child has called exec

In linux, after calling fork(), my child process is going to call exec soon. Is there a way for the parent process to wait() and not do anything till the child has exec'ed?

Thanks.

Upvotes: 2

Views: 1338

Answers (3)

wildplasser
wildplasser

Reputation: 44250

There is no (API) way for the parent to know that the child is performing an exec().

But there is a nice pipe-trick: have the child inherit a filedescriptor (for a pipe) and (before the fork() ) set the close-on-exec flag for the pipe. The parent will be notified by an EOF on the pipe when it is closed by the exec().

Please note that this does not need any collaboration from the child.

Upvotes: 4

twalberg
twalberg

Reputation: 62519

Use vfork() instead of fork(). That causes the parent to be suspended until the child either exits or calls one of the execve() family of functions.

Upvotes: 4

Ed Heal
Ed Heal

Reputation: 60037

You need to use waitpid using the process ID returned from the fork call that is returned to the parent.

EDIT

Or if you mean that you want to know that the child is about to call exec use pause in the parent. Get the child to call kill with a suitable signal to the parent (whose process ID can be obtained from getppid). USR1 signal might be useful to use. Do this just before the exec.

Upvotes: 1

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