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Force Input in User Defined Variable

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# 1  
Old 06-19-2007
Force Input in User Defined Variable
In a line such as:

Code:
echo -n "How many days back would you like to check? "; read days

How can I ensure that the user has a.) entered a number between 1-30 (not 0 or 31+) and b.) has not just hit enter (ie set it to "") and if it's entered wrong, how do I start the if statement over?

I think I figured out my first question while typing. I have:
EDIT: I didnt figure it out at all Smilie
Code:
if [ "$days" != [1-30] ]; then  #this doesnt work
echo "Please specify a number between 1 and 30."
echo -n "How many days back would you like to check? "; read days
else
...
fi

If they enter it wrong again, it errors. Is there a better way to do this?
Last edited by earnstaf; 06-19-2007 at 03:24 PM..
# 2  
Old 06-19-2007
It should be something like:

Code:
echo -n "How many days back would you like to check? "; read days

while [ "$days" -lt 1 -o "$days" -gt 30 ]
do
  echo "Please specify a number between 1 and 30."
  echo -n "How many days back would you like to check? "; read days
done

Regards
# 3  
Old 06-19-2007
Quote:
Originally Posted by Franklin52
It should be something like:

Code:
echo -n "How many days back would you like to check? "; read days

while [ "$days" -lt 1 -o "$days" -gt 30 ]
do
  echo "Please specify a number between 1 and 30."
  echo -n "How many days back would you like to check? "; read days
done

Regards
EDIT: Just reread your advice. Sounds good... I'll give it a try.

EDIT2: Works well Franklin. Thanks for the input... I guess I need to get out of the mindset of only using if as the test construct?
Last edited by earnstaf; 06-19-2007 at 04:52 PM..
# 4  
Old 06-19-2007
Earnstaf,
You already have a solution for your problem with the loop offered
by Franklin.
The loop assures you that only numbers between 1 and 30 are entered.
# 5  
Old 06-19-2007
Also, you could test for the condition you actually want...
while [ ${days} -gt 1 ]; do
# 6  
Old 06-19-2007
To assure the input isn't an empty string replace the while statement with:

Code:
while [ "$days" == "" ] || [ "$days" -lt 1 -o "$days" -gt 30 ]

BTW The use of the testoperator -o fails with:

Code:
while [ "$days" == "" ] -o [ "$days" -lt 1 -o "$days" -gt 30 ]

Does somebody have an explanation of that?
I'm home now and using Bash version 3.1.17, does this fail in ksh too?

Regards
# 7  
Old 06-19-2007
Quote:
Originally Posted by earnstaf
In a line such as:

Code:
echo -n "How many days back would you like to check? "; read days

How can I ensure that the user has a.) entered a number between 1-30 (not 0 or 31+) and b.) has not just hit enter (ie set it to "") and if it's entered wrong, how do I start the if statement over?

I think I figured out my first question while typing. I have:
EDIT: I didnt figure it out at all Smilie
Code:
if [ "$days" != [1-30] ]; then  #this doesnt work
echo "Please specify a number between 1 and 30."
echo -n "How many days back would you like to check? "; read days
else
...
fi

If they enter it wrong again, it errors. Is there a better way to do this?

Code:
while :
do
  printf "Enter day of month (1 - 30): "
  read day
  case $day in
    *[^0-9]* | "" | ???* )
       printf "Invalid number: \"%s\"\nPlease try again.\n\n" "$day"
       continue
       ;;
  esac
  if [ $day -gt 30 -o $day -lt 1 ]
  then
     printf "\nInvalid number: \"%s\"\nPlease try again.\n\n" "$day"
     continue
  fi
  break
done
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