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?
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.
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!
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
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 $?, which will return 0 confirming successful without any mistake.
It worked for me well. I ran on Linux OS, Bash Shell.
I actually check all bash scripts in current dir for syntax errors WITHOUT running them using find tool:
Example:
find . -name '*.sh' -print0 | xargs -0 -P"$(nproc)" -I{} bash -n "{}"
If you want to use it for a single file, just edit the wildcard with the name of the file.
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=$i
done
set -
For only validating syntax:
shellcheck [programPath]
For running the program only if syntax passes, so debugging both syntax and execution:
shellproof [programPath]
Bash shell scripts will run a syntax check if you enable syntax checking with
set -o noexec
if you want to turn off syntax checking
set +o noexec
There is BashSupport plugin for IntelliJ IDEA which checks the syntax.
If you need in a variable the validity of all the files in a directory (git pre-commit hook, build lint script), you can catch the stderr output of the "sh -n" or "bash -n" commands (see other answers) in a variable, and have a "if/else" based on that
bashErrLines=$(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
Related
I want to run this script:
#!/bin/bash
echo <(true)
I run it as:
sh file.sh
And I get "Syntax error: "(" unexpected" . I found some similar situations but still can't solve this.
I'm a beginner at shell scripting , but as I understand:
the shebang I use is correct and chooses the bash shell , so the process substitution syntax should work
I try the same from the command line and it works. I checked with echo $0 and it gives me "bash" , so what's the difference from running the command in the command line and from a script that invokes the same shell?
Maybe it's something simple, but I couldn't find an explanation or solution.
You should run your script with bash, i.e. either bash ./script.sh or making use of the shebang by ./script.sh after setting it to executable. Only running it with sh ./script.sh do I get your error, as commented by Cyrus.
See also: role of shebang at unix.SE
Remove export POSIXLY_CORRECT=1 from your ~/.bashrc or ~/.profile (etc.) files.
The issue is that process substitution is an added bash feature that is not part of the posix standards.
sh file.sh
errorsh: 3: Syntax error: "(" unexpected
solution:
bash file.sh
I am writing shell script to install my application. I have more number of commands in my script such as copy, unzip, move, if and so on. I want to know the error if any of the commands fails. Also I don't want to send exit codes other than zero.
Order of script installation(root-file.sh):-
./script-to-install-mongodb
./script-to-install-jdk8
./script-to-install-myapplicaiton
Sample script file:-
cp sourceDir destinationDir
unzip filename
if [ true]
// success code
if
I want to know by using variable or any message if any of my scripts command failed in root-file.sh.
I don't want to write code to check every command status. Sometimes cp or mv command may fail due to invalid directory. At the end of script execution, I want to know all commands were executed successfully or error in it?
Is there a way to do it?
Note: I am using shell script not bash
/* the status of your last command stores in special variable $?, you can define variable for $? doing export var=$? */
unzip filename
export unzipStatus=$?
./script1.sh
export script1Status=$?
if [ !["$unzipStatus" || "$script1Status"]]
then
echo "Everything successful!"
else
echo "unsuccessful"
fi
Well as you are using shell script to achieve this there's not much external tooling. So the default $? should be of help. You may want to check for retrieval value in between the script. The code will look like this:
./script_1
retval=$?
if $retval==0; then
echo "script_1 successfully executed ..."
continue
else;
echo "script_1 failed with error exit code !"
break
fi
./script_2
Lemme know if this added any value to your scenario.
Exception handling in linux shell scripting can be done as follows
command || fallback_command
If you have multiple commands then you can do
(command_one && command_two) || fallback_command
Here fallback_command can be an echo or log details in a file etc.
I don't know if you have tried putting set -x on top of your script to see detailed execution.
Want to give my 2 cents here. Run your shell like this
sh root-file.sh 2> errors.txt
grep patterns from errors.txt
grep -e "root-file.sh: line" -e "script-to-install-mongodb.sh: line" -e "script-to-install-jdk8.sh: line" -e "script-to-install-myapplicaiton.sh: line" errors.txt
Output of above grep command will display commands which had errors in it along with line no. Let say output is:-
test.sh: line 8: file3: Permission denied
You can just go and check line no.(here it is 8) which had issue. refer this go to line no. in vi.
or this can also be automated: grep specific line from your shell script. grep line with had issue here it is 8.
head -8 test1.sh |tail -1
hope it helps.
I want to run this script:
#!/bin/bash
echo <(true)
I run it as:
sh file.sh
And I get "Syntax error: "(" unexpected" . I found some similar situations but still can't solve this.
I'm a beginner at shell scripting , but as I understand:
the shebang I use is correct and chooses the bash shell , so the process substitution syntax should work
I try the same from the command line and it works. I checked with echo $0 and it gives me "bash" , so what's the difference from running the command in the command line and from a script that invokes the same shell?
Maybe it's something simple, but I couldn't find an explanation or solution.
You should run your script with bash, i.e. either bash ./script.sh or making use of the shebang by ./script.sh after setting it to executable. Only running it with sh ./script.sh do I get your error, as commented by Cyrus.
See also: role of shebang at unix.SE
Remove export POSIXLY_CORRECT=1 from your ~/.bashrc or ~/.profile (etc.) files.
The issue is that process substitution is an added bash feature that is not part of the posix standards.
sh file.sh
errorsh: 3: Syntax error: "(" unexpected
solution:
bash file.sh
I have this shell script which I use to back up my system. There is a line:
tar -Pzcpf /backups/backup.tar.gz --directory=/ --exclude=proc --exclude=sys --exclude=dev/pts --exclude=backups --exclude=var/log / 2> >(grep -v 'socket ignored' >&2)
As you can see, I have been trying to filter out the annoying, useless "socket ignored" error by tar, using this blog post.
What I get from shell upon execution is:
/bin/sysback: line 45: syntax error near unexpected token >'
/bin/sysback: line 45:tar -Pzcpf /backups/backup --directory=/
--exclude=proc --exclude=sys --exclude=dev/pts --exclude=backups --exclude=var/log / 2> >(grep -v 'socket ignored' >&2)'
The syntax you've used is a bash extension to the basic shell syntax, so you must take care to run your script with bash. (Ksh also has >(…) process substitution but doesn't support it after a redirection. Zsh would be fine.)
Given the error message you're getting, you are running this script in bash, but in its POSIX compatibility mode, not in full bash mode. Take care to invoke your script with an explicit #!/bin/bash line. #!/bin/sh won't do, even if /bin/sh is a symbolic link to bash, because bash runs in POSIX mode if it's invoked under the name sh. Always invoke bash by name if you use bash features.
Also take care not to set the environment variable POSIXLY_CORRECT or to pass the --posix option on the command line if you want to use bash features.
Alternatively, don't use this bash-specific syntax; use a portable construct such as the one proposed by Stephane Rouberol.
How about:
tar -Pzcpf /backups/backup.tar.gz --directory=/ \
--exclude=proc --exclude=sys --exclude=dev/pts \
--exclude=backups --exclude=var/log 2>&1 | grep -v 'socket ignored'
I have found that on gentoo also if sh is a link to /bin/bash if you call the script with 'sh "scriptname"' it doesn't run it as a bash script and fail with:
matchmorethan.sh: line 34: syntax error near unexpected token `<'
matchmorethan.sh: line 34: `done < <( cat $matchfile )'
So if you need to use the Process Substitution feature you need to specifically run it with bash. But I didn't find any reference to this.
Actually you don't have to go for such a redirection in std error when GNU tar provides options to ignore the "socket ignored" warning.
tar --warning='no-file-ignored' -Pzcpf /backups/backup.tar.gz --directory=/ --exclude=proc --exclude=sys --exclude=dev/pts --exclude=backups --exclude=var/log / 2> new.err
You could find the original link with more ignore options here
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?
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.
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!
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
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 $?, which will return 0 confirming successful without any mistake.
It worked for me well. I ran on Linux OS, Bash Shell.
I actually check all bash scripts in current dir for syntax errors WITHOUT running them using find tool:
Example:
find . -name '*.sh' -print0 | xargs -0 -P"$(nproc)" -I{} bash -n "{}"
If you want to use it for a single file, just edit the wildcard with the name of the file.
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=$i
done
set -
For only validating syntax:
shellcheck [programPath]
For running the program only if syntax passes, so debugging both syntax and execution:
shellproof [programPath]
Bash shell scripts will run a syntax check if you enable syntax checking with
set -o noexec
if you want to turn off syntax checking
set +o noexec
There is BashSupport plugin for IntelliJ IDEA which checks the syntax.
If you need in a variable the validity of all the files in a directory (git pre-commit hook, build lint script), you can catch the stderr output of the "sh -n" or "bash -n" commands (see other answers) in a variable, and have a "if/else" based on that
bashErrLines=$(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