Thread: Remove whitespaces from char*

Post your code. Basically, set all the whitespace characters into a string of their own, and then use strstr() to find them. If a subsequent strstr() call returns an adjacent address to the prior saved address, you found a character you can remove.

If you work on your character array from right to left, it's easier.

Todd

You need to make your own (or find one on the "interweb").

It's probably good practice to learn by making your own. The essential principle is that you need a read and a write position in the string, you then read a character. If it's not a space, write it. Continue this until you are at the end of the string. If you want to do exactly trim, then you will need to:
1. use "isspace()" to identify whitespace characters in the string.
2. Identify when you reach the first non-space character and stop removing spaces.
3. When you reach the end of the string, walk back across any whitespace and terminate the string after the point of non-space. [You can of course "remember the last non-space"].

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Mats

That will remove ALL spaces, which is not what "trim" does, but yes, that works.

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Mats

Code:

char* trim(char*s)
{
    char *end = s + strlen(s)-1;
    while(*s && isspace(*s))
        *s++ = 0;
    while(isspace(*end))
        *end-- = 0;
    return s;
}

Nice robust and portable solution, returns the start of the trimmed string. Should not be used on dynamically allocated strings, except if the pointer to the string trimmed start is stored at a different variable.

I have a theory: Programmers are such egomaniacs, you can post a homework question without any proof of effort, and eventually someone will give you the complete answer while trying to show off his expertise.

Originally Posted by Prelude

I have a theory: Programmers are such egomaniacs, you can post a homework question without any proof of effort, and eventually someone will give you the complete answer while trying to show off his expertise.

I think your theory is right... Particularly if you post to many enough forums.

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Mats

Originally Posted by Prelude

I have a theory: Programmers are such egomaniacs, you can post a homework question without any proof of effort, and eventually someone will give you the complete answer while trying to show off his expertise.

I am sorry but to not be misunderstood, firstly it didn't seem like a homework question, secondly even if it was, then the person doing the assignment might use a black box function to get him started, and thirdly the replies up to then were probably more confusing than a simple clean answer itself.
I don't recall any assignment that is about trimming strings, and i understand the purpose of the forum. But a familiar tool can always help someone to solve an unfamiliar problem.

>firstly it didn't seem like a homework question
"Homework" is generally used here as a catchall term for stuff you should attempt to solve on your own before asking for a solution. More often than not it refers to tasks that any sane programmer would use an existing library to accomplish, yet for some reason the "homeworkee" wants to do manually.

>the replies up to then were probably more confusing than a simple clean answer itself
I don't disagree, but you'll also notice that the OP didn't ask for clarification.

>I don't recall any assignment that is about trimming strings
I've seen them before. In fact, I've seen a lot of assignments that involve string processing, and trim is one of the more basic ones.

Originally Posted by Prelude

I have a theory: Programmers are such egomaniacs, you can post a homework question without any proof of effort, and eventually someone will give you the complete answer while trying to show off his expertise.

I don't study IT at college (though I most probably plan to), so it's not a homework. I'm still in highschool and it's just a hobby of mine.

And..um..what kind of homework would be to remove whitespaces ? It that what it's like studying IT at school ? Solving this kind of puzzles ?

P.S. Thanks everyone for your help. My own (not sure actually if it's my own cause I read much of it from another forum) code was something like this:

Code:

char *trim_spaces (char *str, int c)
{
	if (str != NULL)
	{
		char ch = (char)c;
		char *a, *b;
		for (a = str; *a == ch; a++); str = a;

		for (b = str; *b != ch; b++) ; *b = '\0';
		return str;
	}
	else return str;
}

Best wishes, Des

Homework can be all sorts of things, and it's obviously not always easy to determine what is homework or not. By the way, I didn't even suggest it was homework, I just didn't want to give you the code, because writing it yourself would be the best way to learn how to do things with strings.

Of course, finding the solution on another forum only teaches you better google skills, not programming skills.

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Mats