[c++] Search in a string

hylke · 06-13-2004, 10:57 AM

Hello
I want to read evrything between " and " in a string, how do i do that?
So if i have 'hello "test" another' in a string it puts
'test' in an other string.
Thanks Hylke

Majjj · 06-13-2004, 12:23 PM

Try this code :-

string s1 = ("hello \"test\" another");
char c = '"';

int a = s1.find(c,0);
int b = s1.find(c,a+1);

if(a<0 || b<0)
cout << "Pattern not found" << endl;
else {
string s2(s1,a+1,b-a-1);
cout << s2 << endl;
}

Now string s2 has the result.

majjj

phlogistonjohn · 06-13-2004, 01:03 PM

I can think of a couple of ways to do it... depends on how robust you want to make it, and how many sub-strings you want to be able to match. Here is a cheezy example I whipped up using a few string.h functions.

Code:

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

#define MAXSTR 128
#define START 0
#define END 1

int main (void)
{
        int index;
        char* position [2];

        char mystring [MAXSTR] = "this is an \"example\" string\n";
        char deststr [MAXSTR];


        //initialise the boundry pointers
        position[START] = NULL;
        position[END] = NULL;

        //find index of begin and end quotes
        position[START] = strchr( mystring, '"');  //first quote mark
        position[END] = strrchr( mystring, '"');  //last quote mark



        if( position[START] > 0 && position[END]  > 0 &&
                        position[START] < position[END] )
        {
                strncpy( deststr, position[START]+1,
                                position[END]-position[START]-1 );
                //since we're only copying part of the string
                //we need to fill in the null byte ourselves
                deststr[  position[END]-position[START]-1  ] = 0;
        }
        else
        {
                printf("Error case\n");
                return 1;
        }


        printf( "OLD STRING: %s\n", mystring );
        printf( "NEW STRING: %s\n", deststr );


        return 0;
}

I hope you can build off that.

hylke · 06-13-2004, 01:15 PM

Thanks all you guys, i'il use majjj's code.
But there's only one thing i don't understand:

Code:

                string s2(s1,a+1,b-a-1);

What does it do?
Thanx Hylke

Majjj · 06-14-2004, 03:37 AM

hi

Code:

                string s2(s1,a+1,b-a-1);

s2 (string, start, size)

this means the constructor takes the string (here its s1)and copies the content from start to start+size into s2.

a is the first occurance of "
b is the second

so the size of becomes b-(a+1)

I hope this helps

Majjj

hylke · 06-14-2004, 11:20 AM

Thanx, i finaly understand it