Bash script accepting variables in valid number format

Shell Programming and Scripting
1

Hi Experts
I would like to ask if there is a way to validate if the variable passed is in this kind of sample format "06-10" or "10-01". It was really a challenge to me on how to start and echnically the "6-10" stands for "June 10" and "10-01" stands as "October 1", overall it needs to have like of a "Month-Day" valid in number format. I would like to have an if-then statement that would validate if the variables passed are in correct, something like these:

#!/bin/bash 
# This script will ONLY accept two parameters in number format  
# according to "MM-DD" which is "XX-XX"  # To run this script: ./script.sh xx-xx xx-xx 
DATE1=$1 
DATE2=$2
 if [DATE1 is in correct format] && [DATE2 is in correct format]  
   then   
     echo "Correct format"   
     echo "DATE1 = $DATE1"   
     echo "DATE2 = $DATE2"  
   else   
     echo "Not correct format"    
    exit 1 
  fi
2

Welcome to the forum.

Very similar problems have been solved umpteen times in these forums. Did you use the search function, or have a look into the links at the bottom left under "More UNIX and Linux Forum Topics You Might Find Helpful"?

Date / time arithmetics is one of the worst tasks in IT, as many subtleties have to be covered / taken care of. It's not just checking we have two two-digit numbers separated by a dash. Certain months allow for certain days only. Do you need leap year dates considered?
You can use numerical comparisons, or string matching, for validations. What be your favorite?

3

No leap year tests here - would be impossible without knowing the year for each of the dates.

#!/bin/bash
MDAYS=(0 31 29 31 30 31 30 31 31 30 31 30 31)

function valid-mm-dd ()
{
     MONTH=${1%-*}
     DAY=${1#*-}
     MONTH=${MONTH#0}
     DAY=${DAY#0}

     [[ $MONTH =~ ^[0-9]{1,2}$ ]] || return
     [[ $DAY =~ ^[0-9]{1,2}$ ]] || return
     (( MONTH > 0 && MONTH < 13 )) || return
     (( DAY > 0 && DAY <= MDAYS[MONTH]))  || return
}
DATE1=$1
DATE2=$2

if valid-mm-dd $DATE1 && valid-mm-dd $DATE2
then
   echo "Correct format"
   echo "DATE1 = $DATE1"
   echo "DATE2 = $DATE2"
else
   echo "Not correct format"
   exit 1
fi
1 Like
4

@Chubler_XL - suggestion is the answer here:b: