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Groups > comp.os.linux.misc > #35737

Re: correct quoting for variables in bash scripts?

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Barry Stir <scooter@mealteam6.mil> wrote:
> 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?

Hi Barry.

be aware that these forms are not equivalent.

"$LINK1_DIR" and "${LINK1_DIR}" are - kind of - equivalent and
$LINK1_DIR and ${LINK1_DIR} are.

The version with curly brackets is more secure since if you have a
variable "LINK1" defined

  echo "-$LINK1_DIR-"

either triggers an error or just prints "--" while

  echo "-${LINK1}_DIR-"

prints "-<LINK1 contents>_DIR-" and vice versa if you have a variable
"LINK1_DIR" defined.

Regards
    Henning
-- 
It doesn't matter whether you win or lose -- until you lose.

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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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