Bash/Linux if elif else issue

Question

Currently working on my bash skills. I've done a few activites based on if/elif/else given to me to my tutor but can't put my finger on the one below.

Basically I'm tasked with outputting the following based on the input of a grade. Less than 40% = Fail 40% to 59% = Pass 60% to 69% = Merit 70% and above = Distinction

It seems to get caught on the first elif, presents the grade as merit for anything below 70 and doesn't check the others, it gives the same result when I change the order too.

echo "Please enter your grade"
read GRADE
echo

     if [ $GRADE -ge 70 ]; then
         echo "Well done, you got a distinction"

    elif [ $GRADE -ge 60 ] || [ $GRADE -le 69 ]; then
          echo "Well done, you got a merit"
    elif [ $GRADE -ge 40 ] || [ $GRADE -le 59 ]; then
          echo "Well done, you got a pass"
    else 
          echo "Unfortunately you failed"
      fi

Your statement uses || (logical OR), rather than && (logical AND). — Brett Hale
– Brett Hale, Commented Mar 28, 2017 at 19:08
Thank you! I knew it would be a basic syntax error and needed fresh eyes! — Will
– Will, Commented Mar 28, 2017 at 19:11
In fact, you can omit the [ $GRADE -le ... ] completely. The order of the the elifs already ensures that the grade is less than .... — Socowi
– Socowi, Commented Mar 28, 2017 at 19:12
Pretty much any number is either >= 60 or <=69. You have a logical error there. — twalberg
– twalberg, Commented Mar 28, 2017 at 21:02

clt60 · Accepted Answer · 2017-03-28 20:34:32Z

1

A bit unusual solution

#bash 4.0+
while read -r -p 'Grade? (h-help)> ' grade
do
    case "$grade" in
        q) echo "quitting..." ; exit 0 ;;
        h) echo "Enter numeric value (0..100) or q for quit" ;&
        '') continue ;;
        *[!0-9]*) echo "Must be numeric value" ; continue ;;
    esac
    case 1 in
        $((grade > 100)) ) echo "impossible" ;;
        $((grade >= 70)) ) echo "distinction" ;;
        $((grade >= 60)) ) echo "merit" ;;
        $((grade >= 40)) ) echo "pass" ;;
                        *) echo "fail" ;;
    esac
done

answered Mar 28, 2017 at 20:34

clt60

64.3k17 gold badges114 silver badges206 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

jwvh · Accepted Answer · 2017-03-28 19:26:26Z

0

Your problem is in using || (or) rather than && (and). If you put in "10", 10 is LESS THAN 69 so it will drop into the first else.

Using set -x at the top of your script will help you figure this sort of thing out.

edited Mar 28, 2017 at 19:26

jwvh

51.3k7 gold badges42 silver badges70 bronze badges

answered Mar 28, 2017 at 19:11

Senor CMasMas

12 bronze badges

Comments

komar · Accepted Answer · 2017-03-28 19:43:07Z

0

There better to use -a for AND and -o for OR in []. And do something like this:

if   [ $GRADE -lt 40 ]; then
    echo "Unfortunately you failed"
elif [ $GRADE -ge 40 -a $GRADE -lt 60 ]; then
    echo "Well done, you got a pass"
elif [ $GRADE -ge 60 -a $GRADE -lt 70 ]; then
    echo "Well done, you got a merit"
else
    echo "Well done, you got a distinction"

answered Mar 28, 2017 at 19:43

komar

8815 silver badges8 bronze badges

Comments

Troyan · Accepted Answer · 2017-03-29 09:42:24Z

0

your problem came from the || (or), you need to use && (and). For exemple 65 is greater than 60 AND lesser than 69.

echo "Please enter your grade"
read GRADE
echo

 if [ $GRADE -ge 70 ]; then
     echo "Well done, you got a distinction"

elif [ $GRADE -ge 60 ] && [ $GRADE -le 69 ]; then
      echo "Well done, you got a merit"
elif [ $GRADE -ge 40 ] && [ $GRADE -le 59 ]; then
      echo "Well done, you got a pass"
else
      echo "Unfortunately you failed"
  fi

answered Mar 29, 2017 at 9:42

Troyan

1191 silver badge7 bronze badges

2 Comments

Charles Duffy Over a year ago

Lots of bugs still present than this. If the user enters -e . -o 1 as their grade, then they'll be told they got a distinction with no error, because the test invocations will look at whether . exists before they do any numeric comparisons at all. Quoting will cause such cases to (correctly) result in a failure with an error: if [ "$GRADE" -ge 70 ]

Charles Duffy Over a year ago

Moreover, all-caps variable names are used for variables with meaning to the OS or shell; names with at least one lowercase character are guaranteed not to conflict with names meaningful to POSIX-specified tools. See pubs.opengroup.org/onlinepubs/9699919799/basedefs/…, fourth paragraph.

Collectives™ on Stack Overflow

Bash/Linux if elif else issue

4 Answers 4

Comments

Comments

Comments

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

4 Answers 4

Comments

Comments

Comments

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related