CIS 71 (section 1): Homework 8 - Hints

1. Using command line parameters
   Here is an example of a program that makes sure that you have a command line parameter and prints out its value:

        #include <stdio.h>
        int main (int argc, char *argv[]){
           if (argc != 2) {
              printf("Usage: %s filename\n", argv[0]);
              exit(0);
           }
           printf("You have typed:\n"
                  "\t%s %s\n", argv[0], argv[1]);
   

   For example, if this program is compiled into a.out we will have:

        % a.out
        usage: a.out filename
   
        % a.out hmw8.c
        You have typed
            a.out hmw8.c
   

2. Printing out a text file
   Here is a program that prints out a text file [just like the cat command]:

   
      #include <stdio.h>
      int main (int argc, char *argv[]){
         FILE *fp;
         char c;
   
         if (argc != 2) {
            printf("Usage: %s filename\n", argv[0]);
            exit(0);
         }
   
         if ((fp = fopen(argv[1], "r"))==NULL) {
           perror("fopen");
           exit(1);
         }
         while((c=getc(fp))!=EOF)
           putchar(c);
         fclose(fp);
      }