Using case for a range of numbers in Bash

Question

I am trying to do the following using case in Bash (in Linux).

If X is between 460 and 660, output X information.

If X is between 661 and 800, do something else.

Etc.

Right now this is what I have:

case $MovieRes in
    [461-660]*) echo "$MovieName,480p" >> moviefinal ;;
    [661-890]*) echo "$MovieName,720p" >> moviefinal ;;
    [891-1200]*) echo "$MovieName,1080p" >> moviefinal ;;
    *) echo "$MovieName,DVD" >> moviefinal ;;
esac

But somehow many of the ones that are 480p, 720p or 1080p are ending with DVD instead. The variable $MovieRes is a simple list that shows, for each line, a number between 1 and 1200. Depending on the value, case decides which "case" to apply.

I would like to know how to actually use case to accomplish this since it is a bit confusing when dealing with ranges like this.

Stacystadholder

"But somehow many of the ones" ... I'm not quite sure which ones are being referred to here. Can you clarify? – Clique

Answer 1

In bash, you can use the arithmetic expression: ((...))

if ((461<=X && X<=660))
then
    echo "480p"
elif ((661<=X && X<=890))
then
    echo "720p"
elif ((891<=X && X<=1200))
then
    echo "1080p"
else
    echo "DVD"
fi >> moviefinal

Yore

Answer 2

The bash case statement doesn't understand number ranges. It understands shell patterns.

The following should work:

case $MovieRes in
    46[1-9]|4[7-9][0-9]|5[0-9][0-9]|6[0-5][0-9]|660) echo "$MovieName,480p" >> moviefinal ;;
    66[1-9]|6[7-9][0-9]|7[0-9][0-9]|8[0-8][0-9]|890) echo "$MovieName,720p" >> moviefinal ;;
    89[1-9]|9[0-9][0-9]|1[0-1][0-9][0-9]|1200)       echo "$MovieName,1080p" >> moviefinal ;;
    *)                                               echo "$MovieName,DVD" >> moviefinal ;;
esac

However, I'd recommend you use an if-else statement and compare number ranges as in the other answer. A case is not the right tool to solve this problem. This answer is for explanatory purposes only.

Primacy

Thank you dogbane. Now here is the problem, you answer correctly answered what I was looking for, but as you also mentioned, this would not be the correct way of doing it. The correct/easier way would be to use Kev's answer. Should I: 1. Accept your answer as the correct answer and give Kev a +1 or 2. Should I accept Kev answer as the correct one and give you a +1. I ask since you both somehow answer correctly. – Stacystadholder

IMO kev's answer should be accepted because that is what you (and anyone else coming to this site) should be using. But I wouldn't mind a +1! Thanks :) – Primacy

Answer 3

Just for the pleasure of subverting case to do as you want, you can use $((...))

case 1 in
    $(($MovieRes<= 460)))echo "$MovieName,???";;
    $(($MovieRes<= 660)))echo "$MovieName,480p";;
    $(($MovieRes<= 890)))echo "$MovieName,720p";;
    $(($MovieRes<=1200)))echo "$MovieName,1080p";;
                       *)echo "$MovieName,DVD";;
esac >> moviefinal

Angers

Huh, it looks like case 1 in essentially equals case true in? That is, a case is met if the formula returns true? This is a cool use of case! – Thermoelectric

Nice answer! Actually we don't need $ in parentheses: $((MovieRes<=1200)) will work – Lorca

$/${} is unnecessary on variables inside arithmetic expressions. Source: shellcheck.net/wiki/SC2004 – Xenomorphic

Answer 4

I was looking for the simplest solution and found it difficult to use a case statement with a number range .

Finally i found a really simple solution for zsh :

  #!/usr/bin/zsh 

 case "${var}" in

 <0-5461>)

 printf "${var} is between 0 and 5461"

 ;;

 <5462-10922>)

printf "${var} is between 5462-10922"

 ;;

 esac

and for Bash :

  #!/bin/bash

 case $((   

(var >= 0 && var <= 5461)      * 1 +   

(var > 5462 && var  <= 10922)   * 2)) in   

(1) printf "${var} is between 0 and 5461";; 

(2) printf "${var} is between 5461 and 10922";; 

esac

Hope it helps someone .

Older

Your zsh solution was exactly what I was looking for! Thank you so much! – Andreasandree

Answer 5

Similar issue which might be useful to someone ... Random additional thing I just tried out where it checks also that it is an integer, for me I wanted it to have a preset value, let the user change it, if they input the wrong data it sets to default.

    func_set_num_files(){
        echo "How many files do you want to create? (input a number 1-10000)"
        read X
        # 1, is it a number, #2 is it within max range?
        if [[ $X != *[!0-9]* ]]; then

            if ((1<=X && X<=10000)) ;then
                        echo "NUM_FILES=$X"
                        NUM_FILES=$X
                else
                        echo "Invalid input, setting to default value [ $NUM_FILES ].";sleep 3
            fi

        else
            echo "Invalid input, non-numeric values entered, setting to default value [ $NUM_FILES ].";sleep 3
        fi

    }

Another example using 'case' to check that a variable is in a range of integers :

check that $MAX is a number and that it's between 50-100 :

            case $MAX in
                ''|*[!0-9]*)
                    echo "The value $MAX is not a number !"
                    exit 1
                ;;
                *)
                    if [ $MAX -lt 50 ] || [ $MAX -gt 100 ] ;then
                        echo "The value $MAX is not between 50-100"
                        exit 1
                    fi
                    echo "Looks like we are good !"
                ;;
            esac

Messenia

Thanks for coming up with a way to state numerical range(s) in a case statement, rather than just suggesting that it needs to be an if. :-) – Buttermilk

Answer 6

This is another solution (may be useful for anybody else):

function caseInRange {
  if [ $1 -ge $2 ]; then
    if [ $1 -lt $3 ]; then echo "$1"; else echo "too high"; fi
  else
    echo "to low"
  fi
}
case $MovieRes in
  1) echo "$MovieName" >> moviefinal ;;
  "$(caseInRange $MovieRes 460 660)") echo "$MovieName,480p" >> moviefinal ;;
  "$(caseInRange $MovieRes 660 890)") echo "$MovieName,720p" >> moviefinal ;;
  "$(caseInRange $MovieRes 890 1200)") echo "$MovieName,1080p" >> moviefinal ;;
  *) echo "$MovieName,DVD" >> moviefinal ;;
esac

This way you can mix ranges and fixed values.

Staminody