SoloCodigo

19.30:   How can I invoke another program or command and trap its output?

A:   Unix and some other systems provide a popen() function, which
   sets up a stdio stream on a pipe connected to the process
   running a command, so that the output can be read (or the input
   supplied).  (Also, remember to call pclose().)

   If you can't use popen(), you may be able to use system(), with
   the output going to a file which you then open and read.

   If you're using Unix and popen() isn't sufficient, you can learn
   about pipe(), dup(), fork(), and exec().

   (One thing that probably would *not* work, by the way, would be
   to use freopen().)

   References: PCS Sec. 11 p. 169.