Question

I am writing a program that processes the output of another program.

Assume my testing program is called test and I want to process the stdout output of program named file.

In test, I am reading stdin as a file as follows:

FILE *fp;
fp = fopen("/dev/stdin", "r");

This works when I run the following in command line: ./file | ./test.

But I assume I want to use I/O redirection, so: ./file > ./test. How can I handle that in C?

Answer 1

I/O redirection using > is not for piping output from one program into another program. It redirects the output from one program into a file. The command

./file > ./test

runs the program file and creates a new file test that contains the output from file. It does not run a program called test, and in fact it will overwrite one if it exists.