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About linux : Bash-script-process-substitution-Syntax-error-unexpected

Question Detail

I want to run this script:

echo <(true)

I run it as:

sh file.sh

And I get “Syntax error: "(" unexpected” . I found some similar situations but still can’t solve this.
I’m a beginner at shell scripting , but as I understand:

  1. the shebang I use is correct and chooses the bash shell , so the process substitution syntax should work
  2. I try the same from the command line and it works. I checked with echo $0 and it gives me “bash” , so what’s the difference from running the command in the command line and from a script that invokes the same shell?

Maybe it’s something simple, but I couldn’t find an explanation or solution.

Question Answer

You should run your script with bash, i.e. either bash ./script.sh or making use of the shebang by ./script.sh after setting it to executable. Only running it with sh ./script.sh do I get your error, as commented by Cyrus.

See also: role of shebang at unix.SE

Remove export POSIXLY_CORRECT=1 from your ~/.bashrc or ~/.profile (etc.) files.

The issue is that process substitution is an added bash feature that is not part of the posix standards.

sh file.sh

errorsh: 3: Syntax error: “(” unexpected


bash file.sh

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