extracting a substring based on position

This is a discussion on extracting a substring based on position within the C Programming forums, part of the General Programming Boards category; Hi Lets say i have a string "ABCDEFGHIJKLMN" and my requirment is that i need to extract a substring from ...

  1. #1
    Registered User
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    Exclamation extracting a substring based on position

    Hi Lets say i have a string "ABCDEFGHIJKLMN"

    and my requirment is that i need to extract a substring from position 5-10 of the string. how do i do it in C? (i.e FGHIJK)

    Thanks

  2. #2
    Woof, woof! zacs7's Avatar
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    If you're allowed to smash the original string, then just put a null-terminator at 10 and return from 5.

    i.e.,
    Code:
    char * substr(char * str, size_t from, size_t to)
    {
       size_t len = strlen(str);
    
       if(from > len || to > len)
          return NULL;
    
       // end the string at to
       str[to] = '\0';
    
       return &str[from];
    }
    Of course if you don't want to modify the original string, then just use memcpy() in the same sort of fashion. Allocating memory for the substring before you copy it in, (from - to) characters, starting from &str[from].
    Last edited by zacs7; 06-22-2009 at 01:10 AM. Reason: WTF, strncpy()? You mean memcpy(). Noob.

  3. #3
    ATH0 quzah's Avatar
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    You mean like memcpy?
    Code:
    memcpy( tohere, fromhere, len );
    tohere[ len ] = '\0';
    You could of course actually TRY.


    Quzah.
    Hope is the first step on the road to disappointment.

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