Delete char from string?

**samuelmoneill** · 04-23-2009

Is it possible to set an index of a char array (string) to NULL.

I know that you cant do the following:

Code:

int MAXBUFFERSIZE] = 5
char buffer[MAXBUFFERSIZE];
buffer[4] = 't';
buffer[4] = NULL;

Is there a way to set buffer[4] = ''; or null?

**matsp** · 04-23-2009

If you have a string "abcdef" and you want to remvoe 'c' from the string, you need to "cut it out" by copying the first part of the string, skipping the c and then concatenating the rest onto the first part.

--
Mats

**Ideswa** · 04-23-2009

You could make a linked list to store your string in. (Every node stores a char of the string).

**anon** · 04-23-2009

I guess moving a couple of characters from one place to another is simpler than doing a linked list (you'd also need to reimplement all string functions).

**cas** · 04-23-2009

Code:

char buffer[MAXBUFFERSIZE];
buffer[4] = 't';
buffer[4] = NULL;

Assigning NULL as above is incorrect. NULL is a null pointer constant, and not the null character. It's possible that on some systems, depending on how NULL is defined, that will work and do what's expected, but it's not guaranteed. To represent the null character, use either 0 or '\0'.

Just changing NULL to 0 won't solve your problem, but I wanted to point out this (somewhat common) misconception.

Edit: I realize that you knew the above wouldn't be a solution to your problem; but I'm not sure if you understood why.

**ssharish2005** · 04-23-2009

>Is it possible to set an index of a char array (string) to NULL.
Well, it is possible. But you would achieve what you wanted. Like you wanted to skip that index value.

Instead it would just print string up tp the '\0' char. Here is an example

Code:

#include <stdio.h>

int main()
{
    char str[] = { "Its a bit obvious." };
    
    printf("Before placing NULL : %s\n", str);
    
    str[10] = '\0';

    printf("After placing NULL : %s\n", str);
    
    getchar();
    return 0;
}    

/* my output 
Before placing NULL : Its a bit obvious.
After placing NULL : Its a bit
*/

-ssharish

**samf** · 04-24-2009

If you want to delete a character from a string you can try these handy functions I found in a book:

Code:

$ cat testdel.c
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

void strdelcn(char *s, int n, char c);
void strdelc(char *s, char c);

int main ()
{
 char teststr[100];

 memset(teststr, 0, sizeof(teststr));

 strcpy(teststr, "This is my test string.");
 printf("teststr before strdelcn [%s], len[%d]\n", teststr, (int) strlen(teststr));
 strdelcn(teststr, 1, 's');
 printf("teststr after strdelcn [%s], len[%d]\n", teststr, (int) strlen(teststr));

 strcpy(teststr, "This is my test string.");
 printf("teststr before strdelc [%s], len[%d]\n", teststr, (int) strlen(teststr));
 strdelc(teststr, 's');
 printf("teststr after strdelc [%s], len[%d]\n", teststr, (int) strlen(teststr));

 exit (0);

}

/*****
                                 strdelcn()
      This function deletes the specified number of
      occurrences of a given character given from a string.
   Argument list:    char *s        the string to be searched
                     int n          the number of occurrences to delete
                     char c         the character to be deleted
   Return value:     void
*****/
void strdelcn(char *s, int n, char c)
{
   while (*s) {
      if (*s == c && n) {
         strcpy(s, s + 1);
         n--;
      } else {
         s++;
      }
   }
}

/*****
                                 strdelc()
      This function deletes all occurrances of a character from a string.
   Argument list:    char *s        the string to be searched
                     char c         the character to be deleted
   Return value:     void
*****/
void strdelc(char *s, char c)
{
   while (*s) {
      if (*s == c) {
         strcpy(s, s + 1);
      } else {
         s++;
      }
   }
}

$ ./testdel.exe
teststr before strdelcn [This is my test string.], len[23]
teststr after strdelcn [Thi is my test string.], len[22]
teststr before strdelc [This is my test string.], len[23]
teststr after strdelc [Thi i my tet tring.], len[19]

**cas** · 04-24-2009

If you want to delete a character from a string you can try these handy functions I found in a book:

Code:

...
strcpy(s, s + 1);
...

Unfortunately, this is not valid code. You cannot use strcpy() with overlapping objects. It may work on some systems, depending on how strcpy() is implemented, but there are no guarantees.

**quzah** · 04-24-2009

You can however use memmove.

Quzah.

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