Given a starting and ending indices, how can I copy part of a string in C?

Question

In C, how can I copy a string with begin and end indices, so that the string will only be partially copied (from begin index to end index)?

This would be like 'C string copy' strcpy, but with a begin and an end index.

Solution 1

Have you checked strncpy?

char * strncpy ( char * destination, const char * source, size_t num );

You must realize that begin and end actually defines a num of bytes to be copied from one place to another.

Solution 2

Use strncpy

e.g.

strncpy(dest, src + beginIndex, endIndex - beginIndex);

This assumes you've

1. Validated that dest is large enough.
2. endIndex is greater than beginIndex
3. beginIndex is less than strlen(src)
4. endIndex is less than strlen(src)