How to count the number of characters in a command line argument by using and creating a function

Question

I am having trouble understanding how to create a function to count the characters in a command line argument. It only has to compute the result in the 'my_strlen()' function, but to print the result out in main(). I am very new to C, but here is my code so far;

int my_strlen(  char string[]);
{
     strcpy(string, argv[1];
     return 1;
}
int main(int argc, char *argv[])
{
  if(argv != 2)
  {
    printf("You must run this program with an argument\n");
    return 2;
  }
  printf("%d", strlen(string);
  return 0;
}

So as you can see, I am pretty confused, I also didn't know how to store the value of strlen(string) to call it later as its own integer.

Answer 1

Try this simple code.

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

/* Function to calculate length of given string */
int my_strlen(char *input_string)
{
    /* Loop through all the characters in the string till null-terminator */
    int i;
    for(i=0; input_string[i] != '\0'; i++);
    return i;
}

int main(int argc, char *argv[])
{
  int length = -1;
  if(argc != 2) /* Check the number of command line arguments */
  {
    printf("You must run this program with an argument\n");
    return 2;
  }
  else
  {
    /* Your function to calculate length of the string */
    length = my_strlen(argv[1]); 
    printf("Length of command line argument is: %d\n", length);
  }
  return 0;
}

Here
argv[0] is program name.
argv[1] is the argument to the program.