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2010-05-25T14:20:56Z

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==A program to list the command line arguments==

<source lang="cpp">
#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">
#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">

#include <stdio.h>
#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">

#include <stdio.h>
#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">
#include <stdio.h>
#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">

#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). *
*/
#include <stdio.h>
#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">
#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">

#include <stdio.h>
#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">
#include <stdio.h>
#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>

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