Bash: Bad Substitution
Answer : The default shell ( /bin/sh ) under Ubuntu points to dash , not bash . me@pc:~$ readlink -f $(which sh) /bin/dash So if you chmod +x your_script_file.sh and then run it with ./your_script_file.sh , or if you run it with bash your_script_file.sh , it should work fine. Running it with sh your_script_file.sh will not work because the hashbang line will be ignored and the script will be interpreted by dash , which does not support that string substitution syntax. I had the same problem. Make sure your script didnt have #!/bin/sh at the top of your script. Instead, you should add #!/bin/bash For others that arrive here, this exact message will also appear when using the env variable syntax for commands, for example ${which sh} instead of the correct $(which sh)