ecearth3/sources/tm5mp/bin/date_diff

#! /bin/sh

# -----------------------------------------------------
# init
# -----------------------------------------------------

# exit on error
set -e

# program name and location:
call="$0 $*"
case $0 in
  /* ) script=$0 ;;
  *  ) script="`/bin/pwd`/$0" ;;
esac
bindir=`/usr/bin/dirname ${script}`
prog=`/bin/basename ${script}`


# -----------------------------------------------------
# help
# -----------------------------------------------------

DisplayHelp ()
{
${PAGER:-less} << EOF

NAME
  $prog - return number of days between two dates

USAGE
  $prog <ccyymmdd1> <ccyymmdd2>
  
EOF
exit 0
}

# err 'help text'
err ()
{
  echo "$1" 1>&2
}

# errit <exit-status>
errit ()
{
  err "$prog - ERROR - in call : ${call}"
  err "$prog - ERROR - use '$prog --help' for more info."
  exit $1
}



# -----------------------------------------------------
# arguments
# -----------------------------------------------------

day1=''
day2=''

# extract arguments
for arg in "$@" ; do
  case ${arg} in
    -h | --help ) DisplayHelp  ;;
    * ) # task or (one of the) location(s)
      if [ -z "${day1}" ]; then
        day1=${arg}
      elif [ -z "${day2}" ]; then
        day2=${arg}
      else
        err "$prog - ERROR - unknown argument : ${arg}"
        errit 1
      fi
      ;;
  esac
done

# not complete ?
if [ -z "${day2}" ]; then
  err "$prog - ERROR - missing arguments"
  errit 1
fi


# -----------------------------------------------------
# begin
# -----------------------------------------------------

# day2 should be equal to or later than day1
if [ ${day2} -lt ${day1} ]; then
  err "$prog - day2 should not be earlier than day1 :"
  err "$prog -    ${day1} ${day2}"
  errit 1
fi

# count from day1 to day2
day=${day1}
nday=0
while [ ${day} -ne ${day2} ]; do
  nday=`/usr/bin/expr ${nday} + 1`
  day=`${bindir}/date_add ${day} 1`
done

# return number of days
echo ${nday}
  
# ok
exit 0
  
# -----------------------------------------------------
# end
# -----------------------------------------------------