CODEWITHSUNDEEP
linuxbashunixsyntaxgnu
Tom Feiner
Tom Feiner

Reputation: 21366

How do I syntax check a Bash script without running it?

Is it possible to check a bash script syntax without executing it?

Using Perl, I can run perl -c 'script name'. Is there any equivalent command for bash scripts?

Upvotes: 329

Views: 305094

Answers (10)

Mike
Mike

Reputation: 31

Bash shell scripts will run a syntax check if you enable syntax checking with

set -o noexec

if you want to turn off syntax checking

set +o noexec

Upvotes: 3

Gerald Hughes
Gerald Hughes

Reputation: 6159

I actually check all bash scripts in current dir for syntax errors WITHOUT running them using find tool:

Example:

find . -name '*.sh' -print0 | xargs -0 -P"$(nproc)" -I{} bash -n "{}"

If you want to use it for a single file, just edit the wildcard with the name of the file.

Upvotes: 6

Alberto Salvia Novella
Alberto Salvia Novella

Reputation: 1250

For only validating syntax:

shellcheck [programPath]

For running the program only if syntax passes, so debugging both syntax and execution:

shellproof [programPath]

Upvotes: 3

E Ciotti
E Ciotti

Reputation: 4955

If you need in a variable the validity of all the files in a directory (git pre-commit hook, build lint script), you can catch the stderr output of the "sh -n" or "bash -n" commands (see other answers) in a variable, and have a "if/else" based on that

bashErrLines=$(find bin/ -type f -name '*.sh' -exec sh -n {} \;  2>&1 > /dev/null)
  if [ "$bashErrLines" != "" ]; then 
   # at least one sh file in the bin dir has a syntax error
   echo $bashErrLines; 
   exit; 
  fi

Change "sh" with "bash" depending on your needs

Upvotes: 1

dvd818
dvd818

Reputation: 1747

Time changes everything. Here is a web site which provide online syntax checking for shell script.

I found it is very powerful detecting common errors.

enter image description here

About ShellCheck

ShellCheck is a static analysis and linting tool for sh/bash scripts. It's mainly focused on handling typical beginner and intermediate level syntax errors and pitfalls where the shell just gives a cryptic error message or strange behavior, but it also reports on a few more advanced issues where corner cases can cause delayed failures.

Haskell source code is available on GitHub!

Upvotes: 161

Cengiz
Cengiz

Reputation: 4867

There is BashSupport plugin for IntelliJ IDEA which checks the syntax.

Upvotes: 2

mug896
mug896

Reputation: 2025

null command [colon] also useful when debugging to see variable's value

set -x
for i in {1..10}; do
    let i=i+1
    : i=$i
done
set -

Upvotes: 4

andy
andy

Reputation: 7018

bash -n scriptname

Perhaps an obvious caveat: this validates syntax but won't check if your bash script tries to execute a command that isn't in your path, like ech hello instead of echo hello.

Upvotes: 464

Diego Tercero
Diego Tercero

Reputation: 1139

I also enable the 'u' option on every bash script I write in order to do some extra checking:

set -u

This will report the usage of uninitialized variables, like in the following script 'check_init.sh'

#!/bin/sh
set -u
message=hello
echo $mesage

Running the script :

$ check_init.sh

Will report the following :

./check_init.sh[4]: mesage: Parameter not set.

Very useful to catch typos

Upvotes: 42

Jeevan
Jeevan

Reputation: 269

sh  -n   script-name

Run this. If there are any syntax errors in the script, then it returns the same error message. If there are no errors, then it comes out without giving any message. You can check immediately by using echo $?, which will return 0 confirming successful without any mistake.

It worked for me well. I ran on Linux OS, Bash Shell.

Upvotes: 26

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