Re: Scripting for /bin/ksh

[Chavdar Ivanov <ci4ic4%gmail.com@localhost>]

On Wed, 4 Aug 2021 at 22:30, Todd Gruhn <tgruhn2%gmail.com@localhost> wrote:
>
> Thanks for the link, Lewis. I have never seen this site. I DID find a
> book in PDF format
> regarding /bin/ksh programming.
>
> My new problem is testing user rank/id.
>
> I want to see if the user is "root"
>
> if (user != root), then print message and die.

#  [[ $(id -u)  -eq  0 ]] && echo  "you are root"
you are root



>
> This is easy in PERL; I have not done it in /bin/ksh.
> I would also like it to execute this test before running the borg command and
> spitting out junk...
>
> On Wed, Aug 4, 2021 at 2:47 PM J. Lewis Muir <jlmuir%imca-cat.org@localhost> wrote:
> >
> > On 08/02, Chavdar Ivanov wrote:
> > > On Mon, 2 Aug 2021 at 14:16, Todd Gruhn <tgruhn2%gmail.com@localhost> wrote:
> > > >
> > > > Thanks for the code Matt.
> > > > I will try this.
> > > > By 'execute' I mean generate
> > > > ${cmd}
> > > > then execute/do whatever ${cmd} turns out to be.
> > >
> > > Depending on the contents of cmd, you might have to use
> > >
> > > eval ${cmd}
> >
> > Yes, and there's the rub: the corner cases.  To correctly build up
> > a command like this and execute it where spaces and other special
> > characters are parsed correctly, you have to shell-quote cmd before
> > passing it to eval.  See the "Shell-quoting arbitrary strings" section
> > in:
> >
> >   https://www.etalabs.net/sh_tricks.html
> >
> > For example, here's a test program that correctly constructs and
> > executes two commands, touch and ls, to create and list some
> > "interesting" test files:
> >
> > ----
> > #!/bin/ksh
> >
> > set -e
> >
> > # https://www.etalabs.net/sh_tricks.html
> > quote() {
> >   printf %s\\n "$1" | sed "s/'/'\\\\''/g;1s/^/'/;\$s/\$/'/"
> > }
> >
> > # https://dwheeler.com/essays/filenames-in-shell.html
> > nl=$(printf '\nX')
> > nl=${nl%X}
> >
> > f1='test_a space'
> > f2='test_b"double-quote'
> > f3="test_c'single-quote"
> > f4="test_d${nl}newline"
> > f5='test_e\backslash'
> >
> > f1_quoted=$(quote "$f1")
> > f2_quoted=$(quote "$f2")
> > f3_quoted=$(quote "$f3")
> > f4_quoted=$(quote "$f4")
> > f5_quoted=$(quote "$f5")
> >
> > cmd="touch $f1_quoted $f2_quoted $f3_quoted $f4_quoted $f5_quoted"
> > printf 'cmd: %s\n' "$cmd"
> > eval "$cmd"
> > cmd="ls -B1 $f1_quoted $f2_quoted $f3_quoted $f4_quoted $f5_quoted"
> > printf 'cmd: %s\n' "$cmd"
> > eval "$cmd"
> > ----
> >
> > Lewis



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