[SOLVED] Bash question

dth4h · 05-07-2012, 08:16 PM

\/ FORGET THIS, read my second post \/

Code:

while [ $continue = no ];do
read -p "Some question" answer
if [ "$answer" != "1" -a "$answer" != "2" -a "$answer" != "3" -a "$answer" != "4" -a "$answer" != "5" -a "$answer" != "6" -a "$answer" != "y" -a "$answer" != "e" -a "$answer" != "remove" ];then
  echo "Option not recognised"
  continue=no
fi

The third line is the only one that is really relevant. What is a simpler way of writing the third line? Basically instead of it checking for all those numbers, I just want to make sure that it is a number, and that it isn't more then 99.
And for the other options, my Dad said he remembered that he used to do something like this:
if [ "$answer" != [y|e|remove] ];then
but he doesn't remember the exact syntax. And I tried that and it didn't work. So do any of you know the right way of doing that or something similar?

Tinkster · 05-07-2012, 09:21 PM

But you're accepting "e", "y", and "remove", so your text explanation
doesn't match your code ...

dth4h · 05-07-2012, 09:31 PM

Ok forget about everything else. I figured out how to do the number part. I just want to know if there is something similar to this that is right:
if [ "$answer" != [y|e|remove] ];then

This put in a sentence "If the answer is not y, e or remove then"

My long current way of doing this that I want to shorten (because if I have like 20 options then this line could get really long):

Code:

while [ $continue = no ];do
read -p "Some question" answer
if [ "$answer" != "y" -a "$answer" != "e" -a "$answer" != "remove" ];then
  echo "Option not recognised"
  continue=no
fi

NOTE: The options are not important, I just used them as examples.

jlinkels · 05-07-2012, 09:53 PM

This is maybe not very efficient, but it seems elegant:

Code:

correct_answer=0
for test_answer in y n remove spam eggs foo bar
do
  if [ $answer == $test_answer ]
  then
     correct_answer=1
  fi
done
if [ $correct_answer -ne 1 ]
then
   #do something
fi

Beware, this is not tested code, it might contain errors!

jlinkels

dth4h · 05-07-2012, 10:15 PM

Quote:

Originally Posted by jlinkels

This is maybe not very efficient, but it seems elegant:

Code:

correct_answer=0
for test_answer in y n remove spam eggs foo bar
do
  if [ $answer == $test_answer ]
  then
     correct_answer=1
  fi
done
if [ $correct_answer -ne 1 ]
then
   #do something
fi

Beware, this is not tested code, it might contain errors!

jlinkels

This works. I never knew there was "for" to use for loops. I thought there was only while. This is so cool. Thanks

!

I am still curious though if there is a right way of doing what I posted. I know my Dad used to do something like it and I have seen it a few places on the internet before, but when I wanted to use it I could never find it again.

Anyway, thanks again jlinkels.

catkin · 05-07-2012, 11:05 PM

A case statement is more natural and easily allows accepting Y as equivalent to y etc:

Code:

case $answer in
    y | Y | e | E | remove )
        ;;
    * )
        <commands to be run when answer is invalid>
esac

dth4h · 05-07-2012, 11:15 PM

Quote:

Originally Posted by catkin

A case statement is more natural and easily allows accepting Y as equivalent to y etc:

Code:

case $answer in
    y | Y | e | E | remove )
        ;;
    * )
        <commands to be run when answer is invalid>
esac

Thanks catkin, that's even better!

Tinkster · 05-07-2012, 11:21 PM

And a third version ... ;D

Code:

regex="y|e|remove"
answer="y"
if [[ $answer =~ $regex ]]; then echo "Known"; fi
Known
answer="blub"
if [[ $answer =~ $regex ]]; then echo "Known"; fi

Cheers,
Tink

dth4h · 05-07-2012, 11:25 PM

Quote:

Originally Posted by Tinkster

And a third version ... ;D

Code:

regex="y|e|remove"
answer="y"
if [[ $answer =~ $regex ]]; then echo "Known"; fi
Known
answer="blub"
if [[ $answer =~ $regex ]]; then echo "Known"; fi

Cheers,
Tink

I think this is my most favorite thread ever!

Thanks everyone!

Tinkster · 05-08-2012, 12:02 AM

Quote:

Originally Posted by dth4h

I think this is my most favorite thread ever!

Thanks everyone!

In that case show the participants some love, and either click on the
little scales on the far left of their posts, or click the "helpful"
link within their posts ;}

dth4h · 05-08-2012, 12:15 AM

Quote:

Originally Posted by Tinkster

In that case show the participants some love, and either click on the
little scales on the far left of their posts, or click the "helpful"
link within their posts ;}

Oh, that's cool. I will do that.

One note though. A side effect of your solution is that you can enter a lot of other things that aren't in the variable "regex" and the answer will be accepted. I haven't quite been able to figure out the pattern yet but here are some examples:
re
reeeeeeeeeeeeee
er
yre

Tinkster · 05-08-2012, 12:18 AM

Quote:

Originally Posted by dth4h

Oh, that's cool. I will do that.

One note though. A side effect of your solution is that you can enter a lot of other things that aren't in the variable "regex" and the answer will be accepted. I haven't quite been able to figure out the pattern yet but here are some examples:
re
reeeeeeeeeeeeee
er
yre

Easy fix

Code:

regex='^y$|^e$|^remove$'

;0)

dth4h · 05-08-2012, 12:19 AM

Quote:

Originally Posted by Tinkster

Easy fix

Code:

regex='^y$|^e$|^remove$'

;0)

Ahhh, cool. Thanks

grail · 05-08-2012, 03:13 AM

Tink Tink Tink .... you must be getting slack in your old age ... lol .. just kidding:

Code:

regex='^(y|e|remove)$'

I would add that to remove the element of case surprise, I would add:

Code:

case ${answer,,} in

# or

if [[ ${answer,,} =~ $regex ]]

Also, you indicated that there are many options, so to help with creating the regex, I would suggest an array:

Code:

elements=(y e remove)

# or if stored in a file with one option per line
#elements=($(< file_with_options))

IFS="|"
regex="^(${elements[*]})$"
unset IFS

if [[ ${answer,,} =~ $regex ]]; then echo "it's here";fi

# or with the case statement
# IFS="|"
# case ${answer,,} in
#     "${elements[*]}") echo it has an element;;
#     *) echo it does not;;
# esac
# unset IFS

catkin · 05-08-2012, 06:41 AM

Nice, grail, nice

Robust and elegant