How can I implement a timeout with subprocess.Popen()?

[I. Myself]

I want my Python program to invoke a compiled C program, and capture the
text output.
Here's a fragment from a program that works, using subprocess.Popen:

p = Popen(execName, stdout=PIPE)
while(1):
line = p.stdout.readline() # get next line
outfile.write(line)
(Then I test for a certain unique phrase in line, and then break
if it occurs)

The above works fine as long as the target program runs for a little
while and then stops. But what if it does not stop? It might run
forever, with or without outputting any lines. How can I make this
robust? The keyword might not occur. The target might crash. It might
run forever, with or without text output.

Thanks,

Mitchell Timin

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