Thread: Simple Removal of string in string via strtok.

Hello!!!

I want to remove the string "/op" from my inputString. I've tried to do this with strtok but he replaces more things then just /op for example if my inputstring is '/op lalalala operhoofd' it will not only remove '/op' but also the 'op' from 'operhoofd'. So my output is 'lalalala herhfd'

Am I using the wrong command or am I just going all wrong.

The code:

Code:

        strcat(userinfo, strtok(inputText,"/op"));

Greetz!
Vincent

Originally Posted by Vincent Wouters

Am I using the wrong command or am I just going all wrong.

Well, strtok() is destructive of the input in the sense that it chops your string up by zeroing out the delimiters. Sometimes that is useful, other times it is not.

Also, the delimiter string argument to strtok is not a string in the sense that "/op" will just match (and erase) "/op"; it will match '/', 'o', and 'p'. Think of it as an array of characters to match.

To remove a substring, you might want to try something with strstr(). Find the substring you want to remove, then place a null terminator '\0' there and strcat() onto it the remainder from after the eliminated substring.

Code:

#include <stdio.h>
#include <string.h>

void removeSubstr (char *string, char *sub) {
	char *match;
	int len = strlen(sub);
	while ((match = strstr(string, sub))) {
		*match = '\0';
		strcat(string, match+len);
	}
}

int main(int argc, const char *argv[]) {
	char test[] = "okay/op 1234 /opdone";
	removeSubstr(test, "/op");
	puts(test);
	return 0;
}

It struck me later that the code is not very optimal, because it continuously rescans the string. Also, if you feed it this:

Code:

char eg[]= "hellolowworld";
removeSubstr(eg, "low");

You'd end up with "helorld", which might not be what you want. So a better version is:

Code:

void removeSubstr (char *string, char *sub) {
	char *match = string;
	int len = strlen(sub);
	while ((match = strstr(match, sub))) {
		*match = '\0';
		strcat(string, match+len);
                match++;
	}
}

Which does not repeatedly re-scan, and thereby also misses the helorld pitfall.

Originally Posted by Vincent Wouters

Do you know how to remove everything before a certain charachter 2? For Example with a string like C:\test.txt how do your remove everything before '\'?

It's normally done with something like 'Left()'?

Greetz!

Check out strchr() and strrchr(). That and some more stuff with moving pointers/copying/concatenating (like in removeSubstr) will get you there.