Linux – Bash scripting error checking using word count and awk

bashlinuxshell-scripting

Need a light on my script I am doing a word count on a variable get a 0 or bigger value but it seems the script is breaking at on this variable function
count_check=wc -l $TABLE_CHECKS | awk '{print $1}' or the if [ $count_check -eq 0 ] please see my code below.

#!/bin/bash -x
set -e
set -u


#
# Routine to check integrity of the restored backup
#


TABLE_CHECKS="$(mktemp -p .)"

mysqlcheck -e -c --all-databases | grep -e error -e Error > $TABLE_CHECKS 

        # if [ $? -eq 0 ]
            # then
              # echo "mysqlcheck running ..."
            # else
              # echo "mysqlcheck error !"
              # exit 1
        # fi

count_check=`wc -l $TABLE_CHECKS | awk '{print $1}'` 
        if [ $count_check -eq 0 ]
            then
              echo "Tables ok..."
            else
              echo "Error on one or more tables. Check  output file: table_checks.txt"
              cat $TABLE_CHECKS > table_checks-`date +%Y-%m-%d_%Hh%Mm%Ss`.txt
              rm -f $TABLE_CHECKS
              exit 1
        fi

rm -f $TABLE_CHECKS

exit 0


I've tried changing the comparison instead of using -eq I was using = , == .

Need some help from the experts as this is taking more time than it needed.Also other ways to achieve that are welcome as I'm limited in scripting.

Thanks in Advance !

Best Answer

Terminate your awk statement and always use proper quoting when using bash.

Finally, "[" as test is for the Bourne Shell sh; use "[[" when writing Bourne-Again Shell (bash) scripts.

Grep expressions may not work the same way on all systems. I've tried to make yours more generic.

#!/bin/bash -x

# don't set flags unless you know you need 'em. 

#
# Routine to check integrity of the restored backup
#

TABLE_CHECKS="table_checks-`date +%Y-%m-%d_%Hh%Mm%Ss`.txt"
mysqlcheck -e -c --all-databases > $TABLE_CHECKS

# grep can do the work you want in one step.
count_check="$(grep -c -E '(error|Error)' $TABLE_CHECKS)"

# What did you get?
echo "count_check is: \"${count_check}\""

# unnecessary indenting makes this hard to read
if [[ $count_check -eq 0 ]]
then
    echo "Tables ok..."
    rm $TABLE_CHECKS
    exit 0
else
    echo "Error on one or more tables. Check output file: ${TABLE_CHECKS}"
    exit 1
fi

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Difference Between Double and Single Square Brackets in Bash – Scripting Shell POSIX

There are several differences. In my opinion, a few of the most important are:

[ is a builtin in Bash and many other modern shells. The builtin [ is similar to test with the additional requirement of a closing ]. The builtins [ and test imitate the functionality /bin/[ and /bin/test along with their limitations so that scripts would be backwards compatible. The original executables still exist mostly for POSIX compliance and backwards compatibility. Running the command type [ in Bash indicates that [ is interpreted as a builtin by default. (Note: which [ only looks for executables on the PATH and is equivalent to type -P [. You can execute type --help for details)
[[ is not as compatible, it won't necessarily work with whatever /bin/sh points to. So [[ is the more modern Bash / Zsh / Ksh option.
Because [[ is built into the shell and does not have legacy requirements, you don't need to worry about word splitting based on the IFS variable to mess up on variables that evaluate to a string with spaces. Therefore, you don't really need to put the variable in double quotes.

For the most part, the rest is just some nicer syntax. To see more differences, I recommend this link to an FAQ answer: What is the difference between test, [ and [[ ?. In fact, if you are serious about bash scripting, I recommend reading the entire wiki, including the FAQ, Pitfalls, and Guide. The test section from the guide section explains these differences as well, and why the author(s) think [[ is a better choice if you don't need to worry about being as portable. The main reasons are:

You don't have to worry about quoting the left-hand side of the test so that it actually gets read as a variable.
You don't have to escape less than and greater than < > with backslashes in order for them not to get evaluated as input redirection, which can really mess some stuff up by overwriting files. This again goes back to [[ being a builtin. If [ (test) is an external program the shell would have to make an exception in the way it evaluates < and > only if /bin/test is being called, which wouldn't really make sense.

Linux – How to run a command multiple times, using bash shell

I don't think a command or shell builtin for this exists, as it's a trivial subset of what the Bourne shell for loop is designed for and implementing a command like this yourself is therefore quite simple.

Per JimB's suggestion, use the Bash builtin for generating sequences:

for i in {1..10}; do command; done

For very old versions of bash, you can use the seq command:

for i in `seq 10`; do command; done

This iterates ten times executing command each time - it can be a pipe or a series of commands separated by ; or &&. You can use the $i variable to know which iteration you're in.

If you consider this one-liner a script and so for some unspecified (but perhaps valid) reason undesireable you can implement it as a command, perhaps something like this on your .bashrc (untested):

#function run
run() {
    number=$1
    shift
    for i in `seq $number`; do
      $@
    done
}

Usage:

run 10 command

Example:

run 5 echo 'Hello World!'

Best Answer

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