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- Subject: Re: Lua 5.4.2 New assorted suggestions
- From: Sean Conner <sean@...>
- Date: Mon, 16 Nov 2020 17:49:05 -0500
It was thus said that the Great Ranier Vilela once stated:
> Em seg., 16 de nov. de 2020 às 12:41, Andre Leiradella <email@example.com>
> > Not false, since strcmp only goes as far as the first NUL is found in one
> > of the strings.
> Maybe you can then explain why they implemented strncmp, if strcmp solves
> everything and is as fast and better than strncmp?
I know Roberto said not to contribute more to this thread, but I feel that
at least this question can (and probably should) be answered.
"They" were Ken Thompson, Brian Kerningham and Dennis Ritchie, creators of
Unix and C (they were developed in tandem). The early versions of Unix (and
I'm talking about 1974, 1975 or there abouts) the file system of Unix was
still quite simple, and a directory was nothing more than a special file
that allowed 14 bytes for a file name and an integer (two bytes) to point to
the inode, an on-disk structure that contains the actual file contents.
These two fields comprised an entry, and an array of these were the
struct dir directory;
Two functions were developed to help scan and update this structure,
strncmp() and strncpy(). That is why strncpy() does NOT include the NUL
byte if 'n' is reached---to avoid overwriting the inode field. That is why
strncmp() was developed---to help maintain a simple file system. It had a
very particular use case. That is all.