CS256 - Fundamentals of Structured Programming

Displaying exercises/e9/solution/f1.c

#include <stdio.h>

#define K	1024

/**
 * Make a program that takes a filename from the command line, or print the
 * usage message: "Usage: f1 <filename>\n" if it's absent.
 * Open the file and print it out with a leading line number padded to three
 * spaces.  Hint: It would probably be easiest to use fgets to read each line
 * of input from the file.
 */
int main(int argc, char *argv[])
{
  if (argc < 2) {
    printf("Usage: f1 <filename>\n");
    return 1;
  }
  
  FILE *fp = fopen(argv[1], "r");
  if (fp == NULL) {
    printf("Error opening file.\n");
    return 1;
  }
  char buf[K];
  
  int line = 1;
  while(fgets(buf, K, fp) != NULL) {
    printf("%3d %s", line, buf);
    line++;
  }
  
  fclose(fp);
  return 0;
}