time_difference

#!/bin/bash
#A script to find the time difference between two HH:MM:SS formatted
#times

#Check inputs
if [ $# -gt 3 ]
then
   echo "$0 wants 2 or 3 arguments"
   exit 1
fi

#Set times to use
T1=${1:-"00:00:00"}
T2=${2:-"00:00:00"}

#Count : in times
NT1=`echo ${T1} | awk -F":" '{print NF}'`
NT2=`echo ${T2} | awk -F":" '{print NF}'`

#If no colons then assume we have been passed seconds so convert to time
if [ ${NT1} -eq 0 ]
then
    T1=`seconds_to_time ${T1}`
    NT1=`echo ${T1} | awk -F":" '{print NF}'`
fi
if [ ${NT2} -eq 0 ]
then
    T2=`seconds_to_time ${T2}`
    NT2=`echo ${T2} | awk -F":" '{print NF}'`
fi

#Pad start if not passed a full time
if [ ${NT1} -lt 3 ]
then
    diff=$((3-${NT1}))
    for j in ` seq ${diff}`
    do
	T1="00:"${T1}
    done
fi

if [ ${NT2} -lt 3 ]
then
    diff=$((3-${NT2}))
    for j in ` seq ${diff}`
    do
	T2="00:"${T2}
    done
fi
T1="00"${T1}
T2="00"${T2}

#Set symbol to use
SYM=${3:-"-"}

#Validate symbol
VALIDSYM=0
VSYMS=( "-" "+" "m" ) #Array of allowed symbols
for i in ${VSYMS[@]}
do
    if [ "${SYM}" == "${i}" ]
    then
	VALIDSYM=1
	break 
    fi
done

if [ "${SYM}" == "m" ]
then
    SYM="*"
fi

if [ ${VALIDSYM} -eq 0 ]
then
    echo "Error: Invalid operation symbol '${SYM}'"
    exit 1
fi

#Get hours minutes and seconds
h1=`echo $T1|cut -d: -f1`
m1=`echo $T1|cut -d: -f2`
s1=`echo $T1|cut -d: -f3`

h2=`echo $T2|cut -d: -f1`
m2=`echo $T2|cut -d: -f2`
s2=`echo $T2|cut -d: -f3`

#Get total number of seconds
x1=$(($h1*3600+$m1*60+$s1))
x2=$(($h2*3600+$m2*60+$s2))

#This makes sure we take the absolute time difference
#if test $x1 -lt $x2
#then
#    diff=`calc "$x2 ${SYM} $x1"`
#else
    diff=`calc "$x1 ${SYM} $x2"`
#fi

#Now convert back into hh:mm:ss format and print
secs=`echo ${diff} | awk -F "." '{print $1}'`
h=$(( secs / 3600 ))
m=$(( ( secs / 60 ) % 60 ))
s=$(( secs % 60 ))
#h=`calc floor(${secs}/3600)`
MINUS=-1
if [ ${h} -lt 0 ]
then
    h=$((-1*${h}))
    MINUS=1 #`calc -1*${MINUS}`
fi

if [ ${m} -lt 0 ]
then
    m=$((-1*${m}))
    MINUS=1 #`calc -1*${MINUS}`
fi

if [ ${s} -lt 0 ]
then
    s=$((-1*${s}))
    MINUS=1 #`calc -1*${MINUS}`
fi

#Add minus sign
if [ ${MINUS} -eq 1 ]
then
    echo -en "-"
fi

FSTR="%02d:%02d:%02d\n"
printf ${FSTR} ${h} ${m} ${s}

exit 0