How do I syntax check a Bash script without running it?
LinuxBashUnixSyntaxGnuLinux Problem Overview
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?
Linux Solutions
Solution 1 - Linux
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.
Solution 2 - Linux
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.
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!
Solution 3 - Linux
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
Solution 4 - Linux
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 $?, which will return 0 confirming successful without any mistake.
It worked for me well. I ran on Linux OS, Bash Shell.
Solution 5 - Linux
I actually check all bash scripts in current dir for syntax errors WITHOUT running them using find tool:
Example:
find . -name '*.sh' -print0 | xargs -0 -P"$(nproc)" -I{} bash -n "{}"
If you want to use it for a single file, just edit the wildcard with the name of the file.
Solution 6 - Linux
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=$i
done
set -
Solution 7 - Linux
Bash shell scripts will run a syntax check if you enable syntax checking with
set -o noexec
if you want to turn off syntax checking
set +o noexec
Solution 8 - Linux
There is BashSupport plugin for IntelliJ IDEA which checks the syntax.
Solution 9 - Linux
For only validating syntax: > shellcheck [programPath]
For running the program only if syntax passes, so debugging both syntax and execution: > shellproof [programPath]
Solution 10 - Linux
If you need in a variable the validity of all the files in a directory (git pre-commit hook, build lint script), you can catch the stderr output of the "sh -n" or "bash -n" commands (see other answers) in a variable, and have a "if/else" based on that
bashErrLines=$(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