Re: [PATCH 3/4] Fit to Plan 9's ANSI/POSIX compatibility layer

From: brian m. carlson <sandals@crustytoothpaste.net>
Date: Aug 6, 2020, 02:04 UTC
Message-ID: <20200806020407.GR6540@camp.crustytoothpaste.net>
In-Reply-To: <d15ed626de65c51ef2ba31020eeb2111fb8e091f.1596675905.git.gitgitgadget@gmail.com>

On 2020-08-06 at 01:05:03, lufia via GitGitGadget wrote:

> From: lufia <lufia@lufia.org>
> 
> That haven't any commands: cut, expr and printf.

Is this ANSI/POSIX environment the one mentioned at [0]? That page describes it as supporting POSIX 1003.1-1990, which is a bit dated. I think we generally assume one has the 2001 edition or later, so you'll have your work cut out for you.

Show 11 quoted lines

> And its sed(1)'s label is limited to maximum seven characters.
> Therefore I replaced some labels to drop a character.
> 
> * close -> cl
> * continue -> cont (cnt is used for count)
> * line -> ln
> * hered -> hdoc
> * shell -> sh
> * string -> str
> 
> Signed-off-by: lufia <lufia@lufia.org>

I will note that usually the project prefers to have a human's personal name here and in the commit metadata instead of a username. Junio may chime in here with an opinion.

>  command_list () {
> -	eval "grep -ve '^#' $exclude_programs" <"$1"
> +	eval "grep -v -e '^#' $exclude_programs" <"$1"

Is it really the case that Plan 9's grep cannot deal with bundled short options? That seems to be a significant departure from POSIX and Unix behavior. Regardless, this should be explained in the commit message.

>  get_categories () {
> -	tr ' ' '\n'|
> +	tr ' ' '\012'|

Okay, I guess. Is this something we need to handle elsewhere as well? The commit message should tell us why this is necessary, and what Plan 9 does and doesn't support.

Show 9 quoted lines

>  	grep -v '^$' |
>  	sort |
>  	uniq
> @@ -18,13 +18,13 @@ get_categories () {
>  
>  category_list () {
>  	command_list "$1" |
> -	cut -c 40- |
> +	awk '{ print substr($0, 40) }' |

I can tell that you haven't gotten the test suite working because I've added a large number of cut invocations there. I suspect you're going to need to provide a portability wrapper there that implements it using awk, sed, or perl.

Show 6 quoted lines

> +if test -z "$(echo -n)"
> +then
> +	alias print='echo -n'
> +else
> +	alias print='printf %s'
> +fi

Let's avoid an alias here (especially with a common builtin name) and instead use a shell function. Maybe like this (not tab-indented):

  print_nonl () {
    if command -v printf >/dev/null 2>&1
    then
      printf "%s" "$@"
    else
      echo -n "$@"
    fi
  }

Notice also that we prefer the standard form and fall back to the nonstandard form if the system is less capable. I don't know if Plan 9 supports "command -v"; "type" may be preferable, but isn't supported by some other shells (e.g., posh). For portability reasons, we may need to try to run printf and see if it fails.

This is also going to need some patching in the testsuite, since we use printf extensively (more than 1300 times). I do hope you have perl available.

[0] http://doc.cat-v.org/plan_9/4th_edition/papers/ape

-- 
brian m. carlson: Houston, Texas, US