Thread: Mallocin' strlen(argv) into a char*

edit:

gotcha!

Code:

 
s = malloc(strlen(argv[1]) * sizeof(char));

Good afternoon friends. How can I malloc argv in main?

Code:

 
#include <stdio.h> 
#include <stdlib.h> /* for exit() */
#include <string.h> 

void Strcpy(char*, char*);

void Strcpy(char* s, char* t) 
{ 
   while ( (*s++ = *t++) )
   ;     
}

int main(int argc, char** argv) 
{ 
   char* s = malloc(strlen(argv) * sizeof(char));
   
   if(argc < 2) 
   { 
     printf("Please enter [Executable][string]\n");  
     exit(0);
   }
   Strcpy(s, *(argv + 1));
   printf("Clone is %s\n", s);
   
   free(s);
   return 0;
}

I expect that you would malloc space to store pointers to char, then malloc space for each string.

Originally Posted by laserlight

I expect that you would malloc space to store pointers to char, then malloc space for each string.

how would I do that ?

Now I'm getting /strcpy from the output.

Code:

 
./strcpy thames
Clone is /strcpy

Code:

 
#include <stdio.h> 
#include <stdlib.h> /* for exit() */
#include <string.h> 

void Strcpy(char*, char*);

void Strcpy(char* s, char* t) 
{ 
   while( (*s++ = *t++) )
   ;
}

int main(int argc, char** argv) 
{ 
   char* s;
   
   if(argc < 2) 
   { 
     printf("Please enter [Executable][string]\n");  
     exit(0);
   }
   
   s = malloc(strlen(argv[1]) * sizeof(char));
   
   Strcpy(s, (*argv) + 1);
   printf("Clone is %s\n", s);
   
   free(s);
   return 0;
}

Originally Posted by thames

how would I do that ?

Read the comments.

Code:

#include <stdio.h>
#include <string.h> /* strcpy */
#include <stdlib.h> /* malloc */

char **get(int n, int m) /* Malloc the 2D array (n x m) */
{
    int i;
    char** table;

    /* Malloc n char pointers */
    table=malloc(n*sizeof(char *));

    /* For every char pointer, malloc space for the string
    * that they are going to point to    */
    for(i=0 ; i<n ; i++)
         /* *(table+i) is equivalent to table[i] */
        *(table+i)=malloc( m*sizeof(char) );
    return table;
}

int main(void)
{
        int numberOfcharPtrs = 5;

        int spaceForEveryString = 20;

        int i;

        char** arrayOfStrings;

        arrayOfStrings = get( numberOfcharPtrs, spaceForEveryString);

        /* Fill the array with strings */
        for( i = 0 ; i < numberOfcharPtrs ; i++)
                strcpy( arrayOfStrings[i] , "Example for thames from Brazil");


        /* Print all the strings */
        for( i = 0 ; i < numberOfcharPtrs ; i++)
                printf("At index %d we have stored : %s\n",i,arrayOfStrings[i]);

        return 0;
}

Code:

for(j = 1, i = 0; i < MAXCHARS; i++, j++)

How many strings should you copy inside your array?
- I should copy inside be array as many strings as the user gives in the cmd

How many does he input?
- argc
No
- why?
Because argc contains the name of the executable too, so the number is

Code:

argc-1

Originally Posted by std10093

How many strings should you copy inside your array?
- I should copy inside be array as many strings as the user gives in the cmd

I'm using j for that purpose (to start argv at index 1) . I fixed the for:

Code:

 
for(j = 1, i = 0; i < MAXPOINTERS; i++, j++) 
   { 
      Strcpy(s[i], argv[j]);  
   }

But I'm still getting the same error.

edit:

okey-dokey, I fixed this else as you told me:

Code:

 
else if(argc >= MAXPOINTERS) 
   { 
     printf("You can write up to %d words", MAXPOINTERS);
     exit(0);   
   }

The current code:

Code:

 
  #include <stdio.h> 
#include <stdlib.h> /* for exit and malloc*/
#include <string.h> 

#ifndef MAXPOINTERS
  #define MAXPOINTERS 20
#endif 

#ifndef MAXCHARS
  #define MAXCHARS 100
#endif    

void Strcpy(char*, char*);
char** Malloc2D(int, int);

void Strcpy(char* s, char* t) 
{ 
   while( (*s++ = *t++) )
   ;
}

char** Malloc2D(int nPointers, int nChars)
{
   int i; 
   char** strings;
   
   strings = malloc(nPointers * sizeof(char*));
   
   for(i = 0; i < nPointers; i++) 
   { 
     *(strings + i) = malloc(nChars * sizeof(char));  
   }
   
   return strings;            
}     

int main(int argc, char** argv) 
{ 
   int i, j;
   char** s;
   
   
   if(argc < 2) 
   { 
     printf("Please enter [Executable][string]\n");  
     exit(0);
   }
   
   else if(argc >= MAXPOINTERS) 
   { 
     printf("You can write up to %d words", MAXPOINTERS);
     exit(0);   
   }        
   
   s = Malloc2D(MAXPOINTERS, MAXCHARS);
   
   for(j = 1, i = 0; i < MAXPOINTERS; i++, j++) 
   { 
      Strcpy(s[i], argv[j]);  
   }        
   
   printf("The strings which were input are:\n");
   for(i = 0; i < MAXPOINTERS; i++) 
   { 
      printf("%d.\t%s", i, s[i]);   
   }         
   
   return 0;
}

argv[0] containts the executable name, argv[1] will contain the first string and so on...

So what I said before in code is this

Code:

for(j = 1, i = 0; i < argc-1; i++, j++)

Of course do not forget to act likewise for the printing part of your code

Isn't it nice when you find the solution by yourself? ( With some ideas from other people, but still it seems that you did understand )

A last tip : I wouldn't print all the pointers. I would print only how many input I have.
In code

Code:

printf("\nThe strings which were input are:\n");
   for(i = 0; i < MAXPOINTERS; i++) 
   { 
      printf("\n%d.\t%s", i + 1, s[i]);   
   }

This can achieved by modifying the red part

You know you are welcome. Very glad that I helped