work/scripts/irctc_book

   1 #!/bin/bash
   2
   3 PROGNAME="$(basename $0)"
   4 USAGE="$PROGNAME: Usage: $PROGNAME YYYY-MM-DD"
   5 if [ "$#" -ne 1 ]; then
   6     echo "$USAGE"
   7     exit 1
   8 fi
   9
  10 if ! echo "$1" | awk -F- '{
  11     if (NF != 3) {
  12         exit 1
  13     } else if (length($1) != 4) {
  14         exit 1
  15     } else if ((length($2) != 2) || (length($3) != 2)) {
  16         exit 1
  17     }
  18     exit 0
  19 }'; then
  20     echo "$USAGE"
  21     exit 1
  22 fi
  23
  24 GIVEN_DATE=$(date -d "$1") || exit
  25 date -d "$GIVEN_DATE - 90 days" +%F