Write a c function to extract a substring s2 of j characters starting from jth position of a given string s1?

Answer 1

The standard library is your friend here - look for 'strlcpy'

Without error checking, it should look something like this...

// START CODE

// we need an extra char

// for the null character at the end - so we need j + 1 chars

char * s2 = malloc( sizeof(char) * (j + 1 ) );

strlcpy( s2, s1 + j, j + 1 );

// END CODE

Hope this helps.

EDIT:::::::

Oops... strlcpy is not actually part of the C standard library... :(

It ought to be kicking around on most Linux distros...

If your environment does not provide strlcpy, use its cousin, strncpy

to do this with strncpy... (strncpy has poorer error handling than

strlcpy imo, but they operate very similarly)

// START CODE

char * s2 = malloc( sizeof( char ) * ( j + 1 ) );

strncpy( s2, s1 + j, j + 1);

s2[j] = '\0'; // strncpy does not guarantee a null-terminated result :(

// END CODE

Hope this helps - and isn't broken ;)