Copy STDIN to STDOUT

#include<stdio.h>

int main() {
    char c;
    while ((c = getchar()) != EOF) {
        putchar(c);
    }

    return 0;
}

• stdio.h is needed to get the definition of EOF End of file.

gcc copy.c

./a.out
Type some text
Ctrl-D

• On Linux and macOS we can press Ctrl-D on an empty line to send EOF.
• We can also redirect some file. e.g. ./a.out < copy.c will redirect the content of the copy.c file to the STDIN of the program and that will print it to the screen.