C/Development/Command Line Parameters

A program to list the command line arguments

<source lang="cpp">

1. include <stdio.h>

void main(int argc, char *argv[]) {

 int i = 0;
 printf("Program name: %s\n", argv[0]);
 for(i = 1 ; i<argc ; i++)
   printf("\nArgument %d: %s", i, argv[i]);
 return 1;

}

      </source>

Check the command line input

<source lang="cpp">

1. include <stdio.h>

int main(int argc, char *argv) {

 if ( argc > 1 ) 
    printf ( "You have initiated execution with arguments.");

}

      </source>

Check the command line parameter and use it

<source lang="cpp">

1. include <stdio.h>
2. include <stdlib.h>

int main(int argc, char *argv[]) {

 double pounds;
 if(argc!=2) {
   printf("Usage: CONVERT <ounces>\n");
   printf("Try Again");
 }
 else {
   pounds = atof(argv[1]) / 16.0;
   printf("%f pounds", pounds);
 }
 return 0;

}

      </source>

Check the command line parameter: if less than required exit

<source lang="cpp">

1. include <stdio.h>
2. include <stdlib.h>

int main(int argc, char *argv[]) {

 double pounds;
 if( argc != 2 ) {
   printf("Usage: CONVERT <ounces>\n");
   printf("Try Again");
   exit(1); /* stop the program */
 }
 pounds = atof(argv[1]) / 16.0;
 printf("%f pounds", pounds);
 return 0;

}

      </source>

Check the command line parameters

<source lang="cpp">

1. include <stdio.h>
2. include <stdlib.h>

int main(int argc, char *argv[]) {

 if(argc!=2) {
   printf("You forgot to type your name.\n");
   exit(1);
 }
 printf("Hello %s", argv[1]);
 return 0;

}

      </source>

Command line parameter: display all of them

<source lang="cpp">

1. include <stdio.h>

int main(int argc, char *argv[]) {

 int i;
 for(i = 1; i < argc; i++) 
     printf("%s ", argv[ i ]);
 return 0;

}

      </source>

Parse Arguements

<source lang="cpp"> /* Practical C Programming, Third Edition By Steve Oualline Third Edition August 1997 ISBN: 1-56592-306-5 Publisher: O"Reilly

• /

/* This program is an example of how to parse *

* the command line arguments.  It sets up all the  *
* global variables for a real program, it just doesn"t  *
* have any body.          *
**/

/* Program: Print *

*              *
* Purpose:            *
*  Formats files for printing      *
*              *
* Usage:            *
*  print [options] file(s)        *
*              *
* Options:            *
*  -v    Produce versbose messages  *
*  -o<file>  Send output to a file     *
*      (default=print.out)    *
*  -l<lines>  Set the number of lines/page.  *
*      (default=66).      *
*/

1. include <stdio.h>
2. include <stdlib.h>

int verbose = 0; /* verbose mode (default = false) */ char *out_file = "print.out"; /* output filename */ char *program_name; /* name of the program (for errors) */ int line_max = 66; /* number of lines per page */ /*

* do_file -- dummy routine to handle a file            *
*                                                      *
* Parameter                                            *
*      name -- name of the file to print               *
*/

void do_file(char *name) {

   printf("Verbose %d Lines %d Input %s Output %s\n",
       verbose, line_max, name, out_file);

} /*

* usage -- tell the user how to use this program and   *
*              exit                                    *
*/

void usage(void) {

   fprintf(stderr,"Usage is %s [options] [file-list]\n", 
                               program_name);
   fprintf(stderr,"Options\n");
   fprintf(stderr,"  -v          verbose\n");
   fprintf(stderr,"  -l<number>  Number of lines\n");
   fprintf(stderr,"  -o<name>    Set output filename\n");
   exit (8);

} int main(int argc, char *argv[]) {

   /* save the program name for future use */
   program_name = argv[0];
   /* 
    * loop for each option.  
    *   Stop if we run out of arguments
    *   or we get an argument without a dash.
    */
   while ((argc > 1) && (argv[1][0] == "-")) {
       /*
        * argv[1][1] is the actual option character.
        */
       switch (argv[1][1]) {
           /*
            * -v verbose 
            */
           case "v":
               verbose = 1; 
               break;
           /*
            * -o<name>  output file
            *    [0] is the dash
            *    [1] is the "o"
            *    [2] starts the name
            */
           case "o":
               out_file = &argv[1][2];
               break;
           /*
            * -l<number> set max number of lines
            */
           case "l":
               line_max = atoi(&argv[1][2]);
               break;
           default:
               fprintf(stderr,"Bad option %s\n", argv[1]);
               usage();
       }
       /*
        * move the argument list up one
        * move the count down one
        */
       ++argv;
       --argc;
   }
   /*
    * At this point all the options have been processed.
    * Check to see if we have no files in the list
    * and if so, we need to process just standard in.
    */
   if (argc == 1) {
       do_file("print.in");
   } else {
       while (argc > 1) {
         do_file(argv[1]);
         ++argv;
         --argc;
       }
   }
   return (0);

}

      </source>

Process the command line input

<source lang="cpp">

1. include <stdio.h>

int main(int argc, char *argv[]) {

 int t, i;
 for(t=0; t<argc; ++t) {
   i = 0;
   while(argv[t][i]) {
     putchar(argv[t][i]);
     ++i;
   }
   printf("\n");
 }
 return 0;

}

      </source>

Use the command line parameter

<source lang="cpp">

1. include <stdio.h>
2. include <stdlib.h>

int main(int argc, char *argv[]) {

 double pounds;
 pounds = atof(argv[1]) / 16.0;
 printf("%f pounds", pounds);
 return 0;

}

      </source>

Verify the user input and display file content

<source lang="cpp">

1. include <stdio.h>
2. include <stdlib.h>

int main(int argc, char *argv[]) {

 FILE *fp;
 char ch;
 if(argc!=2) {
   printf("You forgot to enter the filename.\n");
   exit(1);
 }
 if((fp=fopen(argv[1], "w"))==NULL) {
   printf("Cannot open file.\n");
   exit(1);
 }
 do {
   ch = getchar();
   putc(ch, fp);
 } while (ch != "$");
 fclose(fp);
 return 0;

}

      </source>