bytesort.c

#define _FILE_OFFSET_BITS 64
#include <string.h>
#include <sys/types.h>
#include <sys/uio.h>
#include <unistd.h>

#define N 16384
int main() {
  ssize_t r, counts[256] = {0};
  unsigned char buf[N];
  while ((r = read(0, (void*) buf, N)) > 0)
    for (ssize_t j = 0; j < r; j++)
      counts[buf[j]]++;
  if (r != 0) return 1;
  for (int i = 0; i < 256; i++) {
    ssize_t count = counts[i];
    memset(buf, i, (count < N) ? count : N);
    for (; count >= N; count -= N)
      if (write(1, buf, N) < 0)
        return 1;
    if (write(1, buf, count) < 0)
      return 1;
  }
}