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Groups > comp.os.linux.misc > #35733

Re: correct quoting for variables in bash scripts?

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On 17.10.2022 at 19:28, Barry Stir scribbled:

> I see various formats, such as
>    if [[ -L ${LINK1_DIR} ]]; then
> 
>    if [[ -L "$LINK1_DIR" ]]; then
> 
> rather than just $LINK1_DIR
> I presume this is insurance to ensure script works in every version
> of Red Hat, Debian, Arch whatever...
> So which is the ideal extra character to put around the environment 
> variable?

There are different reasons for using either notation, and they are not
mutually exclusive.  Portability between distributions is irrelevant in
this regard.

  ° The ${VARIABLE} notation bears preference due to the fact that it
    protects against errors caused by concatenation.

  ° The "$VARIABLE" notation is used when there is a chance of the
    variable containing spaces or other special characters, such as
    e.g. a backslash or a newline character.

Therefore, one can combine the two formats as "${VARIABLE}" if
one suspects that the variable may contain spaces and/or other
special characters AND if the variable is to be concatenated with
either a literal or another variable.

-- 
With respect,
= Aragorn =

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Thread

correct quoting for variables in bash scripts? Barry Stir <scooter@mealteam6.mil> - 2022-10-17 19:28 +0800
  Re: correct quoting for variables in bash scripts? Aragorn <telcontar@duck.com> - 2022-10-17 14:10 +0200
  Re: correct quoting for variables in bash scripts? Ralf Fassel <ralfixx@gmx.de> - 2022-10-17 14:15 +0200
    Re: correct quoting for variables in bash scripts? Jerry Peters <jerry@example.invalid> - 2022-11-01 20:27 +0000
  Re: correct quoting for variables in bash scripts? "Carlos E. R." <robin_listas@es.invalid> - 2022-10-17 14:39 +0200
  Re: correct quoting for variables in bash scripts? Rich <rich@example.invalid> - 2022-10-17 14:02 +0000
  Re: correct quoting for variables in bash scripts? Henning Hucke <h_hucke+spam.news@newsmail.aeon.icebear.org> - 2022-10-17 13:54 +0000
  Re: correct quoting for variables in bash scripts? Eli the Bearded <*@eli.users.panix.com> - 2022-10-17 23:35 +0000
    Re: correct quoting for variables in bash scripts? Ralf Fassel <ralfixx@gmx.de> - 2022-10-18 11:31 +0200
      Re: correct quoting for variables in bash scripts? Rich <rich@example.invalid> - 2022-10-18 12:02 +0000
        Re: correct quoting for variables in bash scripts? Ralf Fassel <ralfixx@gmx.de> - 2022-10-18 15:01 +0200
          Re: correct quoting for variables in bash scripts? Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2022-10-18 14:17 +0000
            The difference between /bin/test and /bin/[ Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2022-10-18 14:58 +0000
              Re: The difference between /bin/test and /bin/[ Eli the Bearded <*@eli.users.panix.com> - 2022-10-21 04:41 +0000
            Re: correct quoting for variables in bash scripts? Ralf Fassel <ralfixx@gmx.de> - 2022-10-19 12:04 +0200

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