Redirecting the output of a child process

Question

There are several ways of redirecting the output of a child process:

1. using freopen(3)
2. using dup(3)
3. using popen(3)

Answer 1

I would expect to find dup2() used mainly.

Neither popen() nor freopen() is designed to handle redirections such as 3>&7. Up to a point, dup() could be used, but the 3>&7 example shows where dup() starts to creak; you'd have to ensure that file descriptors 4, 5, and 6 are open (and 7 is not) before it would handle what dup2() would do without fuss.