[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: printf '%s\n' "$@" versus <<< redirection
From: |
goncholden |
Subject: |
Re: printf '%s\n' "$@" versus <<< redirection |
Date: |
Sun, 19 Feb 2023 17:32:43 +0000 |
------- Original Message -------
On Monday, February 20th, 2023 at 4:32 AM, Kerin Millar <kfm@plushkava.net>
wrote:
> On Sun, 19 Feb 2023 16:25:13 +0000
> goncholden goncholden@protonmail.com wrote:
>
> > ------- Original Message -------
> > On Sunday, February 19th, 2023 at 3:17 AM, Greg Wooledge greg@wooledge.org
> > wrote:
> >
> > > On Sat, Feb 18, 2023 at 10:46:08AM +0000, goncholden wrote:
> > >
> > > > My intention is to use prinf line by line on arguments containing
> > > > newlines. With a newline also introduced between arguments $1 $2 $3 etc.
> > >
> > > This is quite unique. I don't believe I've ever seen someone try to
> > > write a command where each argument is a group of lines, and all of
> > > the groups of lines are supposed to be concatenated together to form
> > > one bigger group of lines.
> > >
> > > For this goal, printf '%s\n' "$@" seems to be the correct choice.
> > >
> > > The <<< "$@" construct is nonsensical. Whatever it does (which is
> > > pretty hard to predict, since it doesn't have a real definition), it
> > > will not serve your goal.
> > >
> > > If you want to avoid a pipeline which would cause your processing loop
> > > to run in a subshell, then your syntax of choice would be:
> > >
> > > while read ...
> > > do
> > > ...
> > > done < <(printf '%s\n' "$@")
> >
> > I have found that nested loops are most clear Consequently, I have either
> > this one
> >
> > Code:
> >
> > # Loop over arguments
> > for arg in "$@"; do
> > # Loop over lines
> > printf '%s\n' "$arg" |
> > while IFS= read -r vl ; do
> > ...
> > done
> > done
> >
> > or this
> >
> > Code:
> >
> > # Loop over arguments
> > for arg in "$@"; do
> > # Loop over lines
> > while IFS= read -r vl ; do
> > ...
> > done < <(printf '%s\n' "$arg")
> > done
>
>
> The use of a process substitution - as in your second example - is typical in
> bash because, by having the while command be run in the initial shell, it's
> immune to the issue of 'disappearing' variables. See
> https://mywiki.wooledge.org/BashFAQ/024 for further details. Whether that
> truly matters in your case depends on what "..." is exactly.
>
> --
> Kerin Millar
One purpose is to pass documentation information with colour designators for
consecutive lines.
var1="
Blue:
-h, --help
Prints help.
Green:
For more details see section 3."
var2="
Examples
Blue:
theone -d DIR
White:
Transfers files to directory DIR"
thefunc "var1" "var2"
Re: printf '%s\n' "$@" versus <<< redirection, alex xmb ratchev, 2023/02/18
- Re: printf '%s\n' "$@" versus <<< redirection, Kerin Millar, 2023/02/18
- Re: printf '%s\n' "$@" versus <<< redirection, alex xmb ratchev, 2023/02/18
- Re: printf '%s\n' "$@" versus <<< redirection, Mike Jonkmans, 2023/02/18
- Re: printf '%s\n' "$@" versus <<< redirection, Kerin Millar, 2023/02/18
- Re: printf '%s\n' "$@" versus <<< redirection, goncholden, 2023/02/19
- Re: printf '%s\n' "$@" versus <<< redirection, Kerin Millar, 2023/02/19
- Re: printf '%s\n' "$@" versus <<< redirection, Greg Wooledge, 2023/02/19
- Re: printf '%s\n' "$@" versus <<< redirection, Kerin Millar, 2023/02/19