CODEWITHSUNDEEP
arraysccharc-strings
user14677223
user14677223

Reputation:

How to remove first 80 characters form a char array?

I've my char array, that has maximum size 1024. Anyway it contains a string of 200 characters. I want to remove exactly the first 80 characters from this 200 characters string. How can I do it?

    char my_array[1024];
     for(int i = 80; i < sizeof(my_array); i+=1)
 {
    my_array[i-80] = my_array[i];
 }

I tryed this, but it doesn't work. Do you know any solution to do this? Thank you everybody for your help!

Upvotes: 0

Views: 233

Answers (2)

12431234123412341234123
12431234123412341234123

Reputation: 1

Instead of changing the array, you could, depending on your need, just create a pointer pointing to the 81th char of the original string, this pointer now points to a string where 80 char are removed. Here a shorter example with just 10 chars removed.

int main(void)
{
  char orig[]="This is a long string";
  char *s=orig+10;
  puts(s);
  return 0;
}

This will print

long string

Character counting problem:

You said you want to remove characters. A char is not the same as a character, which is not simple to define and hard to count. First, you have to know the encoding and the value of CHAR_BIT. Most likely you will use UTF-8 and CHAR_BIT==8. Counting code points is relatively easy, just count the chars which indicate the beginning of a code point (Bit 7 is 0 or Bit 6 is set). But then it gets complicated. You need to be aware of combining characters which are code points that are combined with other code points to create a single character. Which is also harder because, depending on the context, a character can't be combined. Then you need to define how you count. For example, in Korean, multiple simple "characters" can be combined into a single "character" by placing them in a single square, how do you count them? (Disclamer i don't understand Korean and i don't really understand how Korean works.)

Counting character goes beyond this answer, i only want to show you that "removing 80 characters" isn't easy to define.

Upvotes: 0

Vlad from Moscow
Vlad from Moscow

Reputation: 310950

Use the standard C string function memmove. For example

#include <string.h>

//...

memmove( my_array, my_array + 80, strlen( my_array ) - 79 );

The magic number 79 means that you need to copy all characters in the string except 80 characters but including the terminating zero character '\0'.

You need to guarantee that the array indeed contains a string and that the stored string has length (strlen( my_array )) not less than 80 characters.

For example

size_t n = strlen( my_array );
if ( !( 80 < n ) )
{
    myarray[0] = '\0';
}
else
{
    memmove( my_array, my_array + 80, n - 79 );
}

Here is a demonstrative program that removes first 7 characters from a string stored in a character array.

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

int main( void ) 
{
    char s[] = "Hello World";
    size_t n = 6;
    
    puts( s );
    
    memmove( s, s + n, strlen( s ) - n + 1 );
    
    puts( s );
}

The program output is

Hello World
World

Upvotes: 2

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