Implementation of cat from book The C Programming Language 2e

cat.c

#include <stdio.h>
#include <stdlib.h>

int main(int argc, char *argv[]) {
  FILE *fp;
  void filecopy(FILE *, FILE *);

  if (argc == 1) {
    // no input, so copy stdin
    filecopy(stdin, stdout);
  }

  else {
    while (--argc > 0) {
      if ((fp = fopen(*++argv, "r")) == NULL) {
        printf("cat: Can't open file '%s'", *argv);
        return 1;

      } else {
        filecopy(fp, stdout);
        fclose(fp);
      }
    }
  }
  return 0;
}

void filecopy(FILE *ifp, FILE *ofp) {
  int c;
  while ((c = getc(ifp)) != EOF) {
    putc(c, ofp);
  }
}