bash: Bad Substitution
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 $(which sh)
The default shell (/bin/sh
) under Ubuntu points to dash
, not bash
.
me@pc:~$ 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.
Your script syntax is valid bash and good.
Possible causes for the failure:
Your
bash
is not really bash butksh
or some other shell which doesn't understand bash's parameter substitution. Because your script looks fine and works with bash. Dols -l /bin/bash
and check it's really bash and not sym-linked to some other shell.If you do have bash on your system, then you may be executing your script the wrong way like:
ksh script.sh
orsh script.sh
(and your default shell is not bash). Since you have proper shebang, if you have bash./script.sh
orbash ./script.sh
should be fine.