program error :counting length of string

**bigjoke** · 12-25-2005

Hi,
I am a newbie and have been learning this language for only 3 months as a part of university degree. I can't figure out the problem with this code.

It is basically a simple programme which tells a user how many letters he has entered. I have debugged the programme and it all works fine until it reaches the for loop inside string_length_func(string_data) this function. please help as i am stuck quite bad.

cheers

Code:

#include <stdio.h>
#define MAX_SIZE 10

int string_length_func(char string_data[]); //func prorotype

int main(void)
{
	/* Declare a character array to store the string in */
	
	char string_data[MAX_SIZE];
	
        int length_word;
	
	/* Ask the user for a string */
	printf("Enter a word: ");
	scanf("%9s", string_data);
      
        /* calling a      function*/
       
 length_word = string_length_func(string_data);
	
printf("This word contains %d letters",length_word);

int string_length_func(char string_data[])
{
	int element_num =0;

/* here lies the problem as i have checked with debugger and all worked fine until here. */
       

for (element_num = 0;((element_num < MAX_SIZE) &&    !(element_num == 0)) ; element_num ++)

	if (string_data [0] == '\0')
	printf("no letter was entered");


return (element_num);
}

**Salem** · 12-25-2005

> printf("This word contains %d letters",length_word);
> int string_length_func(char string_data[])
You've started on your new funcion before you've finished main().
From the look of things, a closing brace is all that is required.

> !(element_num == 0)
Why would you stop at the first character?
Shouldn't you be testing string_data[element_num] == '\0' ?

**bigjoke** · 12-25-2005

Code:

for (element_num = 0;((element_num < MAX_SIZE) && !(element_num == '\0')) ; element_num ++)

I have changed the for loop condition now...

The output of this program without any error or warning is....

Code:

enter a word: four
the word contains 0 letters //zero

Now what should i do. Should it not say 4. i am so confused.

**Salem** · 12-25-2005

Yeah, but what did you change it to?

**bigjoke** · 12-25-2005

the condition in for loop now states !(element_num == '\0') whearas, before it was plain 0. but it is still not working. and no i am not missing any braces or whatever. its down to the problem with for loop. as it is not working as it should be.

thanks salem

**Salem** · 12-25-2005

"Shouldn't you be testing string_data[element_num] == '\0' ?"
Like I said, your loop always exists on the first iteration with your test. You need to test each character (not each index).

**bigjoke** · 12-25-2005

thanks salem.
i appreciate your help very much. the key was the word "character and index" in your post. I totally mixed them up.

anyways... its working now
bravo Salem. You are the man

**Maragato** · 12-25-2005

Originally Posted by bigjoke

thanks salem.
i appreciate your help very much. the key was the word "character and index" in your post. I totally mixed them up.

anyways... its working now
bravo Salem. You are the man

Please get used to post the right solution after you fix it so al can check

**bigjoke** · 12-25-2005

this is the working for loop. just replace it within original code and viola you have a program which counts the number of characters user has typed in

Code:

for (element_num = 0; 
	(element_num < MAX_SIZE) && !(string_data[element_num] == '\0'); 
	element_num ++);

**dwks** · 12-27-2005

Presumably you ended main() and added a return statement too?

And any part of a for loop can be empty, and since element_num is already 0, you can get rid of this:

Code:

for (element_num = 0;

->

Code:

for ( ;

And you might find

Code:

string_data[element_num] != '\0'

easier to read than

Code:

!(string_data[element_num] == '\0')

This code

Code:

scanf("%9s", string_data);

is making assumptions about the value of MAX_SIZE. I would either use

Code:

scanf("%*s", MAX_SIZE-1, string_data);

or fgets()

Code:

fgets(string_data, MAX_SIZE, stdin);

or, even better

Code:

fgets(string_data, sizeof(string_data), stdin);

And don't forget to remove the newline:

Code:

#include <string.h>

char *p;
fgets(string_data, sizeof(string_data), stdin);
if(p = strchr(string_data, '\n')) *p = 0;

**kermit** · 12-27-2005

Code:

#include <string.h>

char *p;
fgets(string_data, sizeof(string_data), stdin);
if((p = strchr(string_data, '\n'))!= NULL) {
 *p = 0;
}

**Dave_Sinkula** · 12-27-2005

Originally Posted by dwks

This code

Code:

scanf("%9s", string_data);

is making assumptions about the value of MAX_SIZE. I would either use

Code:

scanf("%*s", MAX_SIZE-1, string_data);

Since this makes no sense, that'll leave us with fgets.

**dwks** · 12-27-2005

You can't do that with scanf()? It works with printf().

[edit]
No, you're right: http://www.cplusplus.com/ref/cstdio/scanf.html

How do you do it with scanf(), then?
[/edit]

**Dave_Sinkula** · 12-27-2005

Originally Posted by dwks

How do you do it with scanf(), then?

I believe the general form of the hack is like this.

Code:

   char format[20];
   sprintf(format, "%%%lus", (long unsigned)(sizeof format - 1));
   scanf(format, string_data);

But then that has a similar issue. You can work around it, but this just seems to make a greater case for using fgets.

**dwks** · 12-27-2005

Well, fgets() it is, then.

Code:

if((p = strchr(string_data, '\n'))!= NULL) {

What's wrong with mine?

Code:

if(p = strchr(string_data, '\n'))

Should it be like this?

Code:

if((p = strchr(string_data, '\n')))

But that doesn't make sense -- the FAQ uses this:

Code:

while(file = readdir(dir))

[edit]
No, it doesn't. [edit=2] The FAQ, I mean. [/edit] So it probably does need the extra ()'s, right?

It needs the ()'s to compile with TC 2.01, but of course that means nothing.
[/edit]

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