Re: HISTFILE support for /bin/sh

[RVP <rvp%SDF.ORG@localhost>]

On Sat, 6 Jul 2024, Robert Elz wrote:

>  | Or provide a cmd to write out the history (non-append mode) in the
>  | EXIT handler?
>
> I think that will be possible; if HISTAPPEND gets set, the current
> history buffer will be flushed to the file immediately - it needs to
> be or history order wrt future commands would be broken.   If you
> were to set HISTAPPEND=yes in the exit trap, then (assuming HISTFILE is
> set of course) the history buffer would be flushed, and of course, by
> the time the exit trap is run, no more commands are going to be read,
> so (apart from causing the buffer to be flushed) turning HISTAPPEND
> on wouldn't do anything else.   You'd want to leave it set to prevent
> the shell from writing the history buffer again (destroying your work)
> when the shell exits.

OK, so this is working out quite well so far. I have:

# ~/.profile

```
if [ -n "$NETBSD_SHELL" ]
then    export HISTFILE=$HOME/.sh.hist
        export HISTAPPEND=true
        export HISTSIZE=100000
fi
trap 'suniq.sh "$HISTFILE"' EXIT
```

# ~/bin/suniq.sh

```
#!/bin/sh
#
# Massage NetBSD /bin/sh's history file before running nuniq.awk.

set -eu -o pipefail

F=${1:-$HOME/.sh.hist}
[ -f "$F" ] || exit 0                   # no file

H=$(head -n1 "$F")
[ "$H" = _HiStOrY_V2_ ] || exit 0       # nolle pros.

n=$(who | awk -v U="$(id -nu)" '$1==U { n++ } END { print n+0 }')
[ $n -eq 1 ] || exit 0                  # not final sess.

T=$(mktemp "$F.XXXXXX")
trap '[ -f "$T" ] && rm -f "$T"' EXIT   # clean-up

> "$T" (
echo "$H"                               # signature
sed -Ee '
    # delete 1st line, lines w/ leading blanks.
    # remove trailing blanks.
    1d
    /^(\\040|\\011)/d
    s/(\\040|\\011)+\\012$/\\012/
' "$F" | nuniq.awk && mv -f "$T" "$F"
)
```

# ~/bin/nuniq.awk

```
#!/usr/bin/awk -f

{
        if ($0 in A)
                delete L[A[$0]]
        L[NR] = $0
        A[$0] = NR
}
END {
        for (i = 1; i <= NR; i++)
                if (i in L)
                        print L[i]
}
```

Gets rid of duplicate lines and lines beginning with blanks (just like in
bash). Suggestions for improvement welcome.

-RVP