strchr

This is a discussion on strchr within the C Programming forums, part of the General Programming Boards category; I know that strchr, searches for the first occurences of a char in a string... I just wanted know if ...

  1. #1
    Registered User client's Avatar
    Join Date
    May 2002
    Posts
    12

    Question strchr

    I know that strchr, searches for the first occurences of a char in a string... I just wanted know if I can use this code to count characters in a string as example.

    String: An apple a day keeps the doctor away

    Char to search: a

    Result: Found a 6 times in String.

    1. I have figured out something like this.
    Code:
    #include <string.h>
    #include <stdio.h>
    
    int main(void)
    {
       char string[15];
       char *ptr, c = 'i';
       int i;
    
       strcpy(string, "This is a string");
       ptr = strchr(string, c);
       if (ptr)
          while(ptr)
               {
                ptr = strchr(string, NULL);
                i++;
                }
          printf("Char %c, found %d times in string", c, i);
       else
          printf("Char was not found in string");
    }
    But this code didn't work... so I just need a bugfix in this code could you help me out a little bit ???

    2. How do I get this code to find also the Uppercase and the Lowercase 'A' in this code ?

    Thanks in advance
    Client

  2. #2
    Registered User C_Coder's Avatar
    Join Date
    Oct 2001
    Posts
    523
    Do you have to use strchr? its easy enough to do without it
    Code:
    #include <stdio.h>
    #include <ctype.h>
    
    int main( void )
    {
    	
    	char string[] = "An apple a day keeps the doctor away";
    	char *p = string;
    	char ch;
    	int count = 0;
    	
    	printf( "\nEnter character to search for: ");
    	ch = getchar();
    	ch = tolower( ch ); //ensure ch is lowercase
    
    	// all processing done here
    	while( *p )
    	{
    		if( tolower( *p ) == ch  ) //test ch against a lowercase *p
    			++count;           // if the same increment count
    
    		++p;
    	}
    
    	//display results
    	printf( "\n%c occured %d times in the string \"%s\"\n", ch, count, string );
    
    	return 0;
    }
    All spelling mistakes, syntatical errors and stupid comments are intentional.

  3. #3
    End Of Line Hammer's Avatar
    Join Date
    Apr 2002
    Posts
    6,231
    Or the strchr() method:
    Code:
    #include <string.h>
    #include <stdio.h>
    
    int main(void)
    {
    	char	string[30];
    	char	*ptr, c = 'i';
    	int	i = 0;
    
    	strcpy(string, "This is a string");
    	ptr = strchr(string, c);
    	while ((ptr = strchr(ptr, c)) != NULL)
    		{i++;ptr++;}
    
    	printf("Char %c, found %d times in string", c, i);
    	
    	return (0);
    }
    Three main things wrong with the original code.
    - string was 15 bytes long, but the text strcpy()'d into was 16 bytes. Instant buffer overflow... oops.
    - i was not initialised before use. You must set it to 0 first!
    - incorrect args passed to strchr().

    Have fun.........
    When all else fails, read the instructions.
    If you're posting code, use code tags: [code] /* insert code here */ [/code]

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