unix_system_call.c

#include <unistd.h>
#include <stdlib.h>

#define STDIN  0
#define STDOUT 1
#define STDERR 2

int main (int argc, char** argv) {
  const int buffer_size = 128;
  char buffer[buffer_size];

  // Reads a c-string from standard input
  int nread;
  nread = read(STDIN, buffer, buffer_size);
  if (nread == -1) {
    write(STDERR, "A read error has occurred\n", 26);
  }

  // Writes a c-string to standard output (or to standard error).
  size_t nwrite;
  nwrite = write(STDOUT, buffer, nread);
  if (nwrite == nread) {
    return 0;
  }
  write(STDERR, "A write error has occured on file descriptor 1\n", 46);

  exit(0);
}