Very Computer

Hello Netters,

does anyone of you out there know how I can make sure that I have read an
integer rather than a string?

Example:

#!/bin/sh
echo "How many:"
read a

What if someone answers "990Lines"?

Any help is appreciated !!

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   Klaus Wicovsky                                                  

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        case $a in
                [0-9]*) echo "integer";;
                *) echo "non-integer";;
        esac

</dev/cam
--
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    Davis Centre Rm 3147     |  have a retroactive effect."
 Phone (519) 885-1211 x3499  |                          Ambrose Bierce

Quote:

>Hello Netters,

>does anyone of you out there know how I can make sure that I have read an
>integer rather than a string?

>Example:

>#!/bin/sh
>echo "How many:"
>read a

>What if someone answers "990Lines"?

>Any help is appreciated !!

>--
>   Klaus Wicovsky                                                  

TypeCheck() {

   case $a in

        *[a-z,A-Z]*) type="Non-integer"               ;;
                  *) type="Integer"                   ;;
    esac

Quote:}

while [ "$type" = "Non-integer" ]; do
echo "How many:"
read a
TypeCheck
done

---
sigs are like sound-bites..they never say enough, but frequently

| does anyone of you out there know how I can make sure that I have read an
| integer rather than a string?
|
| Example:
|
| #!/bin/sh
| echo "How many:"
| read a
|
|
| What if someone answers "990Lines"?

Do you mean that you want to accept "990Lines" as an answer and strip
off the word or that you want to reject it because it is not an integer?

If you meant the second, there is an easy solution: a case statement based on
a pattern for integers only:

#!/bin/sh
echo "How many:"
read a
case "$a" in
*[!0-9+-]*|?*[-+]*) echo not an integer ;; # has a character that is neither
                                           # a digit nor a sign or has a sign
                                           # later than the first character
*) echo Now that\'s an integer. ;;
esac

David W. Tamkin   Box 59297   Northtown Station, Illinois  60659-0297

    #!/bin/sh
    echo -n "How many: "
    read a
    if [ `expr length $a = $a : "[0-9]*"` = 1 ]; then
        echo Thanks for this fine integer.
    else
        echo Nope, try again.
    fi

Note that this solution doesn't correctly handle an empty input; this
can be fixed easily.

--

This should work, provided that your sh understands the "[!...]" syntax
for the complement of a character class. (Some older Bourne shells don't!
In this case, you can do something similar with the expr command.)
Note that the order of the cases must not be changed: You have to check
_first_, whether $i contains a character that is not a digit, _then_
whether it contains at least one digit (i.e., that it is nonempty).

--
Uwe Waldmann, Max-Planck-Institut fuer Informatik
Im Stadtwald, D-W6600 Saarbruecken 1, Germany