Debug bash scripts

Place the below lines near the top of the script.
Call debuggerIt in the script from a point where debugging should take place or at the start of the script execution.


OUTBASE="/tmp/${USER}/${0##*/}.log"

#-------------------------------------------
debuggerIt()
{
        test -d ${OUTBASE} || mkdir -p ${OUTBASE}
        exec 5> ${OUTBASE}/${0##*/}.debug
        BASH_XTRACEFD="5"
        PS4='$LINENO: '
        set -x
}
#-------------------------------------------

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more functions

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start of execution.

debuggerIt

more commands

Variable assigments

Validating positional parameters.

The below example will print a usage message if there is no 2nd position paramaeter.

PACKAGE=${2:?$(usage ${SERVERLIST} [Package name:Version:Package file[:Dependent service]])}

Shell scripting: Testing empty variables

$V="xNotEmpty"

if [ x$V = "xNotEmpty" ]
then
       echo "\$V not empty"
else
       echo"\$V is empty"
fi

Or:

if [ "$V" = "" ]
then
      echo "\$V is empty
fi