What is the syntax for removing the characters from a string?

Answer 1

There is no need to remove any characters, simply overwrite the first character with a null terminator.

Example:

#include<stdio.h>

void clear_string (char* pstr) {

if (pstr!=0) pstr[0]='\0';

}

int main (void) {

char str[] = "Hello world!";

printf ("\n%s", str); // prints Hello world! on a new line clear_string (str);

printf ("\n%s", str); // prints an empty string

return 0;

}

Note that the character array, str, will effectively contain the character sequence "\0llo World!\0", however the first null-terminator marks the end of the string, so the rest is simply ignored. There is no point in shrinking an array (even a string) unless you absolutely have to, but even then you can only do that with strings allocated on the heap, like so:

#include<stdio.h>

void clear_heap_string (char** ppstr) {

if (ppstr==0 *ppstr==0) return;

char* pstr = realloc (*ppstr, 1 * sizeof(char));

if (pstr==0) return;

pstr[0] = '\0';

*ppstr = pstr;

}

int main (void) {

char* pstr = malloc (13 * sizeof(char));

*pstr = "Hello world!";

printf ("\n%s", pstr); // prints Hello world! on a new line clear_heap_string (&pstr);

printf ("\n%s", pstr); // prints an empty string

free (pstr);

return 0;

}

Note that if the reallocation fails, pstr will still be pointing at the Hello world! string. For that reason it is simpler to just overwrite the first character with a null-terminator, which is always guaranteed to succeed.