How to beep

sudo modprobe pcspkr
beep

shell script - test

Check if the string is null
test -z $var && echo "The string is null" || echo "The string is not null"

Check if the var1 is greater than var2
test $var1 -gt $var2 && echo "var1 > var2" || echo "var1 < var2"

Check if value is 0
test $var -eq 0 && echo "var1 is 0" || echo "var1 is not 0"

shell script function

No parameter
function_name() {
    statement
}

call function
function_name

---

Parameter

function_name() {

    var=$1

    var2=$2

}

call function

function_name arg1 arg2

---

Return value (1)

function_name() {

    statement

    return 2

}

call function

echo "Return is: $?"

---

Return value (2)

function_name() {

    statement

    return $RET

}

call function

echo "Return is:

$RET"

count from file output

cat file | cut -f 1 | awk '{tot=tot+$1} END {print tot}'