Syntax error: "(" unexpected

Question

While executing the below command directly over the terminal, its working fine:

comm -2 -3 <(sort FileOne.txt) <(sort FileTwo.txt) > myFile.txt

But while trying to execute it via .sh file, its giving error: Syntax error: "(" unexpected

Here is my code:

#!/bin/bash
##this will return the unique lines from the first file.
comm -2 -3 <(sort FileOne.txt) <(sort FileTwo.txt) > myFile.txt

I run the script like this:

sh ./myfilename.sh

Please help me to solve it.

Thanks!

Answer 1

If needed, make the script executable first by running:

chmod +x myfilename.sh

Then, run the script like this:

./myfilename.sh

Or run it explicitly with bash like this:

bash myfilename.sh

(These first two commands are essentially the same, since you have the bash shebang #!/bin/bash at the beginning of your script.)

DO NOT run like this:

sh myfilename.sh

Because then you are running the script with Dash (sh) and not with Bash (since your script has Bash-specific syntax).

Answer 2

The answer is similar to answer already posted, but giving an explanantion.

I thing you are running this script sh code.sh. This means you are using sh to run the script, but the first line (#!/bin/bash) implies it's been written for bash.

On some systems sh and bash are the same, but on others they are not; and, when invoked as sh, Bash turns off some non-POSIX features. So it's important to use the right shell and the right invocation.

Use bash code.sh or better still, make the script executable (chmod a+x code.sh) and then run it directly (./code.sh)