Given a starting and ending indices, how can I cop

问题:

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.

回答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.

回答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)

回答3:

Just use memcpy.

If the destination isn't big enough, strncpy won't null terminate. if the destination is huge compared to the source, strncpy just fills the destination with nulls after the string. strncpy is pointless, and unsuitable for copying strings.

strncpy is like memcpy except it fills the destination with nulls once it sees one in the source. It's absolutely useless for string operations. It's for fixed with 0 padded records.