Re: Rationale for aligning data on even bytes in a Unix shell file?

scott@slp53.sl.home (Scott Lurndal) writes:

Janis Papanagnou <janis_papanagnou+ng@hotmail.com> writes:

In a "C" file (of the Kornshell software) I stumbled across this
comment: "Each command in the history file starts on an even byte
and is null-terminated."
>
I wonder what's the reason behind that even-byte-alignment, on "C"
level or on Unix/files level. Any ideas?

>
Possibly to support 16-bit character sets?

I don't think it supports 16-bit character sets.

Unlike bash history files, which are plain text, ksh history files
are in a binary format.

I don't know whether the format includes any multi-byte integers.
If it does, reading such values directly into memory might be easier
on some platforms if they're aligned.

The relevant source file is src/cmd/ksh93/edit/history.c, in
<https://github.com/ksh93/ksh>.  It has functions to manipulate the
history file, but I don't see a full description of the file format.

--
Keith Thompson (The_Other_Keith) Keith.S.Thompson+u@gmail.com
void Void(void) { Void(); } /* The recursive call of the void */