Alex Rivera | Logout

popen() alternative

Asked 2011-07-19T07:40:49.597
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My question is extension of this one: popen creates an extra sh process

Motives:

1) My program need to create a child which does tail on a file. I need to process the output line by line. That is why I am using popen because it returns FILE *. I can easily fetch single line, do what I need to do and print it.

One problem with popen is that you do not get pid of child (tail command in my case).

2) My program should not exit before its child is done. So I need to do wait; but without pid, I cannot do it.

How can I achieve both the goals?

A possible (kludge) solution: do execvp("tail -f file > tmpfile") and the keep reading that tmpfile. I am not sure how good this solution is, though.

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  1. You can use pipe, a function of the exec* family and fdopen. This is non-standard, but so is popen.
  2. You don't need to wait. Just read the pipe up to EOF.
  3. execvp("tail -f file > tmpfile") won't work, redirection is a feature of the shell and you're not running the shell here. Even if it worked it would be an awful solution. Suppose you have read to the end of the file, but the child process has not ended yet. What do you do?
answered 2011-07-19T08:13:05.737

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