Short C program that repeats a string forever

, updated (originally posted )

I recently wanted a command that would endlessly repeat a string at the command line. Like the yes command, but without newlines.

Update: After I published this, Sven told me about the jot command, which can do exactly what I want. For example:

jot -b abc -s '' 0 | head -c 30
# => abcabcabcabcabcabcabcabcabcabc

Before Sven reached out, I couldn’t find a good way to do this, so I gave up and wrote a short C program to do it. Here’s it is:

#include <stdio.h>
#include <string.h>

int main(int argc, char **argv) {
  if (argc != 2) {
    fprintf(stderr, "error: please supply exactly one argument\n");
    return 1;

  char *arg = argv[1];

  if (strlen(arg) == 0) {
    fprintf(stderr, "error: please no empty strings\n");
    return 1;

  while (fputs(arg, stdout) != EOF) {

  return 0;

Once compiled, I run it like this:

./repeat abc | head -c 30
# => abcabcabcabcabcabcabcabcabcabc

It’s a little slow and probably doesn’t work in some cases, but it was good enough for me. (Now I’ll probably be using jot—thanks again, Sven.)

If this is useful to you, great! That’s why I published it! (You can download it here.)