How to check for bash shell syntax errors in practice?

Question

I need to check whether a set of scripts are syntactically correct. I know there are couple of posts around suggesting to use bash -n <script_name> but I run this and I get nothing out e.g.

good.sh

#!/bin/bash

echo "hello"

bad.sh

#!/bin1/bash1

eco "hello"

If I do:

$ bash -n bad.sh; echo $?
0
$ bash -n good.sh; echo $?
0

So how do you discriminate between good and bad exactly?

As far as bash knows, there may be a command by the name of eco, so this isn't really a syntax error. — Tom Fenech
– Tom Fenech, Commented Nov 27, 2014 at 14:47
OK I see. If you answer and put a bad example I will accept. Thank you. — SkyWalker
– SkyWalker, Commented Nov 27, 2014 at 14:50
I know there are others but they are not specific enough probably. — SkyWalker
– SkyWalker, Commented Nov 27, 2014 at 14:50
dvd818 showed that there is a website you can use: shellcheck.net — Jason Hu
– Jason Hu, Commented Nov 27, 2014 at 14:51

l0b0 · Accepted Answer · 2014-11-27 15:22:21Z

2

bash -n checks whether Bash can parse the code (that is, the syntax is correct), not whether the code is "correct." "Correct" can have a lot of meanings, most of which programs will never be able to verify:

Can be parsed (bash -n).
Finishes without error (if ./script.sh; then [...]; fi).
Prints something which follows a specific format.
Prints something useful.
Any of the above within a specific environment, for example one which has a shell interpreter that lives in /bin1/bash1 and a command eco which shows you the most ecologically friendly beer bottles available within a 5 parsec radius.

answered Nov 27, 2014 at 15:22

l0b0

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1 Comment

shellter Over a year ago

It's too bad the -e option can't be overloaded with -n to indicate something like "check if command is available" (and continue to test for syntax errors).

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