How do I duplicate a file descriptor in C?
Answer: the dup system call. Here’s an example of duplicating the descriptor 1, which refers to the standard out pipe.
#include <unistd.h>
#define WRITE(F, S) write((F), (S), sizeof(S))
int main(void) {
WRITE(1, "This is written to stdout via descriptor 1\n");
int new_stdout = dup(1);
WRITE(new_stdout, "This is written to stdout via new descriptor\n");
return 0;
}By duplicating the file descriptor, we get two references to the same underlying pipe.
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