In Unix Seventh Edition, ls and others read directory entries with fread() and parsed the struct direct themselves in application-mode code. The C library and application mode matter, here.

On the gripping hand, there is no strncpy in the Spinellis 7th Edition source code; 4.2BSD was using strncpy() inside readdir() in 1982, though.

The code for strncpy was in the UNIX kernel since at least V6. It was eventually added to the C library under the name strncpy. Sometimes those entries were processed in userland, e.g., by fsck. The utility of strncpy is noted in the C89 rationale (FWIW I was once a member of X3J11, the C89 standards committee):

"strncpy was initially introduced into the C library to deal with fixed-length name fields in structures such as directory entries. Such fields are not used in the same way as strings: the trailing null is unnecessary for a maximum-length field, and setting trailing bytes for shorter names to null assures efficient field-wise comparisons. strncpy is not by origin a "bounded strcpy," and the Committee has preferred to recognize existing practice rather than alter the function to better suit it to such use."

And I just found this comment from John Mashey (I never met John but he and I both worked under Ted Dolotta, John at Bell Labs and me at ISC in Santa Monica):

https://softwareengineering.stackexchange.com/questions/4380...

"I can answer definitively, since I wrote the originals ~1977, having moved from BTL Piscataway to Murray Hill. They were first named str*n, but were later renamed strn*, as there was some system in BTL that needed first 6 letters of external names to be unique.

I was working on kernel & user code that supported rudimentary per-process accounting, which started with someone else, but needed extensions due to big increase in UNIX systems in computer centers, who wanted more performance analysis. I.e. this was supported by commands like accton(1), acctcms(1),acctcom(1), acctmerge(1) (all in UNIX/TS 1.0, Nov 1978, which was ~Research V7 with first steps of PWB/UNIX influence. Think of that as 1.0, then PWB/UNIX 2.0, then UNIX System III...

The records described in acct(5) held the last 8 characters of the command pathname,truncated if necessary and thus possibly not null-terminated. I found multiple instances of inline code to manipulate these, which seemed a bad idea, so I wrote the str*n functions and replaced the inline code, and also used them in the various commands.

I also thought it was a good idea for better code safety.:-) Sigh."