Problem with argv

[timprograms]

I'm running a linux... actually an android with Terminal IDE installed(amazing app) and I created this program with command line arguments...
I run it no errors, but I want them to be able to add a -h option
I have the =="-h" part but still no luck any help would be great...

#include <stdio.h>
int main(int argc, const char *argv[])
{
if (argc==1)
{
printf("Please add an argument\n");
return 1;
}
if(argc==2 && argv[1]=="-h")
{
printf(" Usage:\n");
printf("./hello [-h] NAME\n");
printf("-h displays help\n");
}
if(argc==2 && (argv[1]!="-h"))
{
printf("Hello, ");
printf(argv[1]);
printf("! Thank You!\n");
}
return 0;
} 

[abhishekm71]

What is the output of the above program if you give -h as the parameter?

[MikeyBoy]

argv[1]=="-h"

That's not how you compare C-style char* strings. Use strcmp.

[vlad from moscow]

#include <stdio.h>
#include <string.h>

int main(int argc, const char *argv[])
{
   if ( argc == 1 )
   {
      printf( "Please add an argument\n" );
      return 1;
   }
   else if ( argc == 2 )
   {
      if ( stdcmp( argv[1], "-h" ) == 0 )
      {
         printf( " Usage:\n" );
         printf( "./hello [-h] NAME\n" );
         printf("-h displays help\n");
      }
      else 
      {
         printf( "Hello, " );
         printf( argv[1] );
         printf("! Thank You!\n");
      }
   }

   return 0;
} 

[andywestken]

With single char switches like -h it is also quite common to use operator[] and a switch statement, like below, rather than strcmp. (The code is also tweaked so it treats arg counts other than 1 or 2, and also switches other than -h, as an error.)

And note that that, for historic reasons, the standard from of main uses char* argv[] rather than const char* argv[].

Andy

#include <stdio.h>

void usage()
{
    const char msg[] =
        "Usage:\n"
        "./hello NAME\n"
        "  displays NAME\n"
        "./hello -h\n"
        "  displays help\n";
    printf("%s", msg);
}

int main(int argc, char* argv[])
{
    if (argc!=2)
    {
        printf("Please provide a single argument\n\n");
        usage();
        return 1;
    }

    if (argv[1][0]=='-')
    {
        switch (argv[1][1])
        {
        case 'h':
        case 'H':
            usage();
            break;
        default:
            printf("invalid switch : %s\n\n", argv[1]);
            usage();
            return 1;
        }
    }
    else
    {
        printf("Hello, %s! Thank You!\n", argv[1]);
    }

    return 0;
}

[kooth]

I highly recommend using getopt (3C) which is the best portable way to handle command line arguments IMO.

[Cubbi]

I like boost.program_options more than the posix getopt
http://www.boost.org/doc/libs/release/doc/html/program_options.html

[timprograms]

Thank you for all your help... It works perfectly but question...
Line #23 & #25 why a 2 dimmensional string...

[timprograms]

Hey vlad I would try your code... but I have to get a copy of string.h, iostream, etc. Does anyone know where I can get this? My compiler didn't build right

[MikeyBoy]

Line #23 & #25 why a 2 dimmensional string...

There's no such thing as a "2 dimensional string". argv is an array of strings. The first member, argv[0], is the name of the application. Each subsequent member of the array is one word from the command line.

I have to get a copy of string.h, iostream, etc. Does anyone know where I can get this?

They're part of the C++ standard library, and should be supplied with any compiler.

[vlad from moscow]

@timprograms

Hey vlad I would try your code... but I have to get a copy of string.h, iostream, etc. Does anyone know where I can get this? My compiler didn't build right

First of all you should decide whether you will write the program in C or C++. If the program will be written in C you need to include header <string.h>. If the program will be written in C++ you need to include header <cstring>. These headers are part of the standard libraries of the compiler. So it will be simply enough to specify them in your program.

[timprograms]

Thank you for you help it worked with the 2d array