Thread: how to use argc and argv

what is the different in use between

Code:

main(void)

and

Code:

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

i knew that
argc :an integer containing a count of the number of words the user typed
argv :an array of pointers to strings, these strings are the actual words the user typed or
an exact copy of them.

but i don't understand what is the importance of argc and argv and how to use them in my program . ?

When you run a program, you are allowed to type other things as well. For instance, when you type something like

Code:

C:\> ren foo.c foo.bak

you are running the command ren (or rename) but with two command-line arguments, "foo.c" and "foo.bak".

Here's a simple and easy tutorial on the usage of argc and argv.

Originally Posted by Salahuddin

but i don't understand what is the importance of argc and argv and how to use them in my program . ?

Pretty much any way you like.... main() is a function like any other. argc and argv (they could actually be named anything you like) are parameters passed into the function, just like any other... The only thing special about them is their origin. They come from the command line you typed to start the program.

C:\> ren foo.c foo.bak

i don't know any thing about this code and how to write it
i saw it alot but i don't understand it
i mean , does the user type this code or the programmer
would you please explain or give me a link explaining this code

The only thing special about them is their origin. They come from the command line you typed to start the program.

i don't get what command line i type to start the program
i just type the source code then run the program
would you please make it clearer

argc :an integer containing a count of the number of words the user typed
argv :an array of pointers to strings, these strings are the actual words the user typed or
an exact copy of them.

how can i use the count of the number of words the user typed?? and the words themselves ??
i'm confused ..

thanks

Ok... before you're ever going to be a programmer, you need to know how to operate the machines you're using...

At your present level you are writing comand line programs. ... The Windows Command Line Interpreter, Batch Files, and Scripting- Using the Command Shell (DOS Prompt) (Click the cute red part!) ... That is programs that run in a text mode window on your desktop. To open a command shell in windows type WIN+R in the run dialog type CMD and click Ok... this is the environment you need to learn how to work with.

A command line is a string of characters that does two things... it starts the program and it feeds preliminary data (options, paths, filenames, etc) into the probram which are then accessible as argc and argv ...

When you compile your programs, you are creating an executable... this is a real program that can be run from the command shell, without your programming IDE even loaded into the system... Needless to say, you need to understand how this works.

i'm working on ubuntu 11.04 so the command shell is the terminal i guess right?
the link you suggest is for windows is there any for linux , or are they the same ?

Originally Posted by Salahuddin

i'm working on ubuntu 11.04 so the command shell is the terminal i guess right?
the link you suggest is for windows is there any for linux , or are they the same ?

The "Command Shell" is a terminal emulator which runs a shell program, in your case(by default), bash.

Yes, it works similarly here.

The argc and argv (or whatever name we can them) are very useful when we want to use the command line parameters.
I will give an example to explain this. (Daily life example)

You must have used the copy command in windows. Here the syntax is copy <source-file> <dest>
Suppose you want to make your own C program for copying one file to another, then either you can take these inputs using conventional scanf() function
or you can command line arguments to take your inputs from the user.

Whatever the user will type during the program run in command line, they will availbale to you in an array (which you can access with the help
of argv pointer: argv is a pointer to an array of pointers, where each element of the array points to the string typed by the user).

I hope you got basic idea about using argc and argv.
Hope this helps

///Regards
Sumit

Originally Posted by Salahuddin

what is the different in use between

Code:

main(void)

and

Code:

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

i knew that
argc :an integer containing a count of the number of words the user typed
argv :an array of pointers to strings, these strings are the actual words the user typed or
an exact copy of them.

but i don't understand what is the importance of argc and argv and how to use them in my program . ?

Perhaps an example will help...


Compile the following code as... myprog

Code:

int main(int argc, char *argv[]);
  { int i;
     printf("arg c = %d\n",argc);
     for i = 0; i < argc; i++)
        printf(" argv[%d] = %s\n",i, argv[i]);

    return 0;
}

Run it from the command line... not your ide... Type.... myprog oldfile.txt newfile.txt -c <Enter>
You should see...
argc = 4
argv[0] = myprog
argv[1] = oldfile.txt
argv[2] = newfile.txt
argv[3] = -c

One of the best ways to understand things is to try them out!

when i open terminal in linux ->>> Salahuddin@ubuntu:~$ <<<<<<<<<<-
is written .. so i have to write --->>>>>>myprog oldfile.txt newfile.txt -c <<<<<<<- after it?
i have tried so but the next line appears saying --->>>>myprog:command not found<<<<-

by the way ,when i finish typing the code on eclipse i just press Ctrl+F11 and the program is run below the same eclipse window in a tab called console
showing me .. ->>>>>>>>>
arg c = 1
argv[0] = /home/salahuddin/SAMP/Getchar() and Putchar()/Debug/Getchar() and Putchar()
<<<<<<
and i can't write anything else in this sub window
so i'm confused .. where to write the code?
please help ..

The problem is that i don't deal with the shell-of ubuntu 11.04- at all , the eclipse environment-which i'm working on- has a Console tab already , so i don't type any code to run the program i just press Ctrl+F11.
if you have a tutorial for dealing with shell ,i'll be grateful.
thanks

Originally Posted by Salahuddin

The problem is that i don't deal with the shell-of ubuntu 11.04- at all , the eclipse environment-which i'm working on- has a Console tab already , so i don't type any code to run the program i just press Ctrl+F11.
if you have a tutorial for dealing with shell ,i'll be grateful.
thanks

Something to think about... no need to answer...

How do you expect to program a computer you don't even know how to operate?