copying argv

[code_lover]

Hello ,
I want to copy argv as strings , I don,t know the size of the arguments .
example .
these are command line arguments

mr james and john .
mr james , isaac .

I don,t know if it is possible copying the address of the names( james ,john and isaac )

[CommonTater]

Of course it is... the argv array is just an array of strings... strlen() will tell you how long they are, strcpy() will make copies... or (although non-standard) _strdup() will allocate memory and hand you a pointer to a copy.

However; there is no need to copy these strings unless you are planning to modify them. They are variables, passed into a function, just like any other variable, passed into a function...

Try this to learn more...

#include <stdio.h>

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

    for (i = 0; i < argc; i++)
       printf("%s (%d)\n",argv[i],strlen(argv[i]));

    return 0; }

This will let you see how your parameters transfer from the command line to your argv string array.

[quzah]

#include<stdio.h>
#include<string.h>
#include<stdlib.h>
int main( int argv, char **argc )
{
    char *dest = NULL;
    int x;
    for( x = 0; x < argv; x++ )
    {
        dest = malloc( strlen( argc[ x ] ) + 1 );
        if( dest )
        {
            strcpy( dest, argc[ x ] );
            printf( "argc[ %d ] is %s\n", x, dest );
            free( dest );
        }
    }
    return 0;
}

Looks about right.


Quzah.

[code_lover]

Hi, Thanks for your reply.

#include<stdio.h>
#include<string.h>
#include<stdlib.h>
int main( int argv, char **argc )
{
    char *dest = NULL;
    int x;
    for( x = 0; x < argv; x++ )
    {
        dest = malloc( strlen( argc[ x ] ) + 1 );
        if( dest )
        {
            strcpy( dest, argc[ x ] );
            printf( "argc[ %d ] is %s\n", x, dest );
            free( dest );
        }
    }
    return 0;
}

Can you please explain this a little bit to me .

dest = malloc( strlen( argc[ x ] ) + 1 );

Is malloc allocating memory locating memory enough for one arquments or can this memory allocated used to store three arquments.
thanks
or is it better to allocate memory to store maximum number of chars.

[CommonTater]

Quzah's code is demonstrating how to allocate memory to copy a string... the malloc call is allocating a memory block big enough to hold each string in the array in turn, copying the string, printing it and then freeing the memory. If you want to copy the entire argv array, you need to make dest into an array of pointers to strings (char *dest[argc])

However, as demonstrated in my post #2 there's no need for all that since argc gives you the number of strings, and argv is already an array of strings, no magic, just a perfectly ordinary array of strings. There's no need to copy them unless you intend to change them...

Try the code in post #2 ... you'll see how it works.

[code_lover]

Thanks , I want to copy many argv , i.e i want to copy the names

mr james and john .
mr james , isaac .

the names (james, john , isaac )
my problem is that I don,t know the size of what I am copying .
I need to allocate memory big enough to hold many strings.

[quzah]

It's impossible to do what you want apparently.


Quzah.

[code_lover]

Ok.
I gat it , I thank I need to count what am trying to copy , then allocate memory for that .
I think that will solve my problem .

[code_lover]

Hello can I get a help on this please, The program complied and ran , it worked and outputed something on the first file , but I get errors saying
[code]
Program received signal EXC_BAD_ACCESS, Could not access memory.

int main(int argc , char **argv[]) {
    
    int i = 0 ;
    int sir_count = 0; // for counting sir and sirs
    for(i = 0; i < argc; i++) {
        
        if( strcmp( argv[i] , "Sir") == 0 ) {  // counting sir 
            ++sir_count;
        }
        if( strcmp( argv[i] , "Sirs") == 0 ) { // counting sirs
             ++sir_count;
             if( strcmp( argv[i+2] , "and") == 0 ) {
                 ++sir_count;
             }
             if( strcmp( argv[i+1][ strlen( argv[i+1] )-1 ] , "," ) == 0  ) {
                 ++sir_count;
                 
                 if( !strcmp( argv[i+3] , "and") ==0 ) {
                 ++sir_count;
                 }
             }
         }
         
    }

    printf("The number of Sir/Sirs in the file is : %d ", sir_count );
    return EXIT_SUCCESS;       
}

[code_lover]

I get errors on the second file.

[iceaway]

I get errors on the second file.

argv[i+2]

You cannot do this (i+2) inside your loop! i will count up to the number of elements in the array argv, so when you put i+2 in there you will try to access elements beyond the size of your array (memory which you don't have access to) at the end of the loop.

[AndrewHunter]

You are exceeding the bounds of your array on your array, argv, on line 12, 15, and 18 strcmp checks.

[code_lover]

If I can't do argv[i+1] , how do I get access to the next argv if I can,t wait for the statement to return to the loop.

[quzah]

You can do it, so long as you make sure i+1 is less than argc.


Quzah.

[code_lover]

You can do it, so long as you make sure i+1 is less than argc.

I don,t understand . passing argv[i+2] , lets say i at that moment is 2 , then argv[i+2] is still the same with argv[4]
Please clear me on this ,Thanks