Re: Bash script problem

From	<tomas@tuxteam.de>
Newsgroups	linux.debian.user
Subject	Re: Bash script problem
Date	2021-08-05 10:10 +0200
Message-ID	<CIGBX-Lf-1@gated-at.bofh.it> (permalink)
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On Wed, Aug 04, 2021 at 08:47:30PM -0700, Gary L. Roach wrote:
> Thanks for the help but I still have the problem of the if statement
> always being true. This time I enclosed the file so you can test it.

Please, don't top quote. It confuses the hell out of me.

Now, I think in your script

  if test A="0 ;  "

should read

  if test "$A" = "0 ;  "

or, in the square bracket version:

  if [ "$A" = "0 ;  " ]

Basically, I'm repeating what Greg wrote, in somewhat other words. Greg's
mails are worth being read twice or three times.

Look carefully. Note a couple of things:

** white spaces around the "=":
   `test' and its fancy cousin `[' are regular programs [1] invoked
   by the shell: what follows are arguments which get interpreted by
   `test', in this case, the args are "$A", = and "0 ;  ", i.e. the
   first arg, an operator (=) and the second arg. As always in the
   shell, the args HAVE TO BE SEPARATED BY WHITESPACE (huh sorry for
   raising my voice :)

** shell is not your regular php
   the shell's power (and strangeness) derives from its text replacement
   model. You have to bear that in mind. When the shell processes a
   line, it does text replacements until it thinks it's ready, then
   it invokes the command (typically a binary somewhere in $PATH, but
   it can be a builtin, an alias or a function). In your case:

     if test "$A" = "0 ;  "

   transforms to

     if test "0 ;  " = "0 ;  "

   ...so the binary `test' gets to see three args (due to the quotes).
   It dutily finishes with exit code 0, meaning "okidoki".

** watch those quotes
   this follows a bit from the above. Imagine what happens if you lose
   the quotes around "$A":

     if test $A = "0 ;  "

   now transforms to

     if test 0 ;   = "0 ;  "

   Now test sees *four* arguments: "0", ";", "=" and "0 ;  ". this
   confuses the hell out of it and it balks at you:

     bash: test: too many arguments

Shell programming is a tad different than Python, Perl, Ruby or what
you have. The textual replacement model takes some thought, but it
rewards you (as long as you use shells for what they were meant to).

I hope that gets you on track :)

And oh, in things shell, read Greg's mails. Perhaps also his wiki [2].

Cheers

[1] Nowadays this is a little white lie: most shells have them
   as builtins, but they are supposed to behave like regular
   programs, for compat. There /is/ a /bin/test, but I can't
   find a /bin/[ on my system anymore.

[2] https://mywiki.wooledge.org/BashGuide/

-- tomás

Thread

Bash script problem "Gary L. Roach" <garyroach719@gmail.com> - 2021-08-05 02:00 +0200
  Re: Bash script problem Greg Wooledge <greg@wooledge.org> - 2021-08-05 02:10 +0200
    Re: Bash script problem "Gary L. Roach" <garyroach719@gmail.com> - 2021-08-05 05:50 +0200
      Re: Bash script problem john doe <johndoe65534@mail.com> - 2021-08-05 09:00 +0200
      Re: Bash script problem <tomas@tuxteam.de> - 2021-08-05 10:10 +0200
        Re: Bash script problem Greg Wooledge <greg@wooledge.org> - 2021-08-05 13:20 +0200
          test vs. [ [was: Bash script problem] <tomas@tuxteam.de> - 2021-08-05 14:00 +0200
            Re: test vs. [ [was: Bash script problem] Greg Wooledge <greg@wooledge.org> - 2021-08-05 14:40 +0200
              Re: test vs. [ [was: Bash script problem] <tomas@tuxteam.de> - 2021-08-05 15:00 +0200
      Re: Bash script problem Greg Wooledge <greg@wooledge.org> - 2021-08-05 14:30 +0200
  Re: Bash script problem Anssi Saari <as@sci.fi> - 2021-08-05 09:40 +0200
    Re: Bash script problem Tixy <tixy@yxit.co.uk> - 2021-08-05 10:30 +0200
      Re: Bash script problem <tomas@tuxteam.de> - 2021-08-05 10:40 +0200
        Re: Bash script problem Greg Wooledge <greg@wooledge.org> - 2021-08-05 14:00 +0200
          Re: Bash script problem "Gary L. Roach" <garyroach719@gmail.com> - 2021-08-05 22:10 +0200
            Re: Bash script problem Greg Wooledge <greg@wooledge.org> - 2021-08-05 22:20 +0200
              Re: Bash script problem "Gary L. Roach" <garyroach719@gmail.com> - 2021-08-06 17:00 +0200
                Re: Bash script problem <tomas@tuxteam.de> - 2021-08-06 17:10 +0200
            Re: Bash script problem David <bouncingcats@gmail.com> - 2021-08-06 01:40 +0200
              Re: Bash script problem Greg Wooledge <greg@wooledge.org> - 2021-08-06 02:10 +0200
                Re: Bash script problem Polyna-Maude Racicot-Summerside <debian@polynamaude.com> - 2021-08-06 02:20 +0200
                Re: Bash script problem Greg Wooledge <greg@wooledge.org> - 2021-08-06 02:30 +0200
                Re: Bash script problem The Wanderer <wanderer@fastmail.fm> - 2021-08-06 03:50 +0200
                Re: Bash script problem Greg Wooledge <greg@wooledge.org> - 2021-08-06 04:10 +0200
              Re: Bash script problem Polyna-Maude Racicot-Summerside <debian@polynamaude.com> - 2021-08-06 02:10 +0200
                Re: Bash script problem Christian Groessler <chris@groessler.org> - 2021-08-06 02:30 +0200
                Re: Bash script problem Christian Groessler <chris@groessler.org> - 2021-08-06 03:00 +0200
                Re: Bash script problem Greg Wooledge <greg@wooledge.org> - 2021-08-06 03:10 +0200
                Re: Bash script problem David <bouncingcats@gmail.com> - 2021-08-06 03:10 +0200
                Re: Bash script problem David <bouncingcats@gmail.com> - 2021-08-06 03:00 +0200
                Re: Bash script problem <tomas@tuxteam.de> - 2021-08-06 09:00 +0200
              Re: Bash script problem David Wright <deblis@lionunicorn.co.uk> - 2021-08-06 05:10 +0200
                Re: Bash script problem David <bouncingcats@gmail.com> - 2021-08-06 05:50 +0200
              Re: Bash script problem Darac Marjal <mailinglist@darac.org.uk> - 2021-08-06 09:20 +0200
  Re: Bash script problem Tom Browder <tom.browder@gmail.com> - 2021-08-06 01:00 +0200

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