Subscript of string

[LotusE]

Hi,

I'm fairly new to C, but I need to program a barcode scanner.

I need a function that allows me to substract a small string from a larger string, but I want to be able to give the starting and end position.

For example:

String= "abcdefgh"

I want to able to get all the letters from position 2 to 5 in the string, for example, so it will give me "bcde".

Is this possible, because I can't find a standard function in C that will allow me to do this.

Thanks in advance for your reply!

Cheers

Steve

 

[LotusE]

I meant of course "Substring" of a string. Not fully awake yet, I think..

 

[sedj]

One way :

int iParentIdx;
int iSubStrIdx;
char szSubStr[16];
char* szParentStr = "abcdefgh";
memset(szSubStr, '\0', sizeof(szSubStr));
iSubStrIdx = 0;
for (iParentIdx = 2; iParentIdx <= 5; iParentIdx++) {
  szSubStr[iSubStrIdx++] = szParentStr[iParentIdx];
}

--------------------------------------------------
Free Java/J2EE Database Connection Pooling Software

http://www.primrose.org.uk

 

[sedj]

Or perhaps memcpy() :

char szParentStr[]= "abcdefgh";
char szSubStr[16];
memset(szSubStr, '\0', sizeof(szSubStr));
memcpy (szSubStr, &szParentStr[2], 3);

--------------------------------------------------
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http://www.primrose.org.uk

 

[cpjust]

I'd prefer strncpy(). That way you don't need the memset() to set szSubStr to all NULLs.

 

[DaveSinkula]

[tt]strncpy[/tt] does not necessarily null terminate a string.

 

[cpjust]

That's only if your string completely fills the buffer, but in that case, you should use a bigger char* buffer anyways.

 

[DaveSinkula]

It doesn't null terminate the string in a particularly relevant case.

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

int main(void)
{
   char a[] = "XXXXXXXXXXXXX", b[] = "hello";
   strncpy(a, b, 4);
   puts(a);
   return 0;
}

/* my output
hellXXXXXXXXX
*/

 

[cpjust]

Oh crap, that'll teach me for posting when I'm in a hurry...

 

[LotusE]

Thanks guys for all your answers!

Cheers

LotusE