Question

I’m writing a C program where I fork() read a file in parent and pass to child via a pipe, then in child redirect the file receive from the pipe to the program I want to execv,

For example, if I exec /bin/less with doc.txt, I will read doc.txt in parent and pass to child, then execute less with the string receive from the read end of pipe.
Everything else is ok, except the execv() part.

I have read the man page for execv(), but it doesn’t really help on doing this…

Any help?

Answer 1

Since any forked child share the parents file descriptors, you can simply redirect stdin to a file descriptor with dup2() then just fork and exec away in your child process.

When the child process reads data from stdin, it’ll read from the file descriptor you opened (which could be a descriptor to your doc.txt).