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I'm new to bash shell scripting and it is my first day and first time to post a question here in stackoverflow. I already searched the archive to no avail. I hope someone can help me.

I have an array like this 

declare -a SID=("mydb1" "mydb2" "mydb3")

In my script, the user will be prompted to enter a string and it will be stored in $DBNAME variable.

For example a user entered "mydb2" (without quote), this will be stored in $DBNAME variable.

I want to create a loop and I want the input of the user to be tested against each element of the ${SID[@]} variable.

And when a match found, it will exit from the loop and continue with the next command in a script.

Please help me create a script to match a string value against each element of an array variable.

Any help would be highly appreciated. Thank you!

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  • What do you want to happen when a match is found? Are you only testing THAT a match is found? Or do you care which match? Commented Oct 28, 2011 at 6:18
  • Hi Mark thank you for your concern. Yes I wanted to test the input of the user and it should be matched with one of the element. Commented Oct 28, 2011 at 6:21

3 Answers 3

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5

@Flimzy's approach is good. The correct way to use a for-loop is

for db in "${SID[@]}"; do
  if [[ $db = $DBNAME ]]; then
    echo yes
    break
  fi
done
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1 Comment

+1, because this answer works as intended... On the other hand, I'll mention Flimzy's answer here (because my comment to his queston is buried at the end of a long list of comments).. Flimsy's answer can give false positives, eg. "mydb1 mydb2"
1

If all you want to do is check that the user entered a valid dbname, do this:

declare -a SID=("mydb1" "mydb2" "mydb3")
case " ${SID[*]} " in
    *\ $DBNAME\ *)
        echo Entered a correct DB name! Good job, pal!
        ;;
    *)
        echo Try again
        ;;
 esac

This can lead to false-positives in cases where you allow space-containing user-input. If this is a concern, you can solve the problem by using a non-space delimiter that is not allowed in the user's input. For example:

case ".mydb1.mydb2.mydb3." in
    *.$DBNAME.*)

If your user input is completely open-ended, and unvalidated, then a for loop is probably your best bet, as explained in @glennjackson's answer.

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7 Comments

I really appreciate that. Thank you! How about if the array values are not explicitly declared in the loop. Something like this, but this one is not working. read -p "Enter DB name :" DBNAME for DB in "${SID[@]}" do if [[ DB != DBNAME ]] ; then printf "Match not found\n" else printf "Match found\n" fi done
You could use a for loop as you suggest, but that's messier if all you care about is finding a match, because you have to keep a temporary variable that you set to true when you find a match, then check that variable after the loop to see if a match was found.
Flimzy and Mark thank you very much. It worked! People like you motivates newbies like me to pursue our goal to learn more. I really appreciate it. In the meantime, I will browse the archive and try to immerse myself with the system. :)
Sure! Tell me how to up-vote and accept your answer. I already clicked the YES button, is that it?
Sorry not enough reputation. Will do next time that's for sure. Thanks again!
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0

If all you want is to check that $DBNAME is an entry is $SID, the easiest thing to do is probably:

if echo ${SID[@]} | grep -wq "$DBNAME"; then
   # DBNAME is in SID array
fi

Note that -w and -q are non-standard options to grep, so you might want:

if echo ${SID[@]} | grep "\<$DBNAME\>" > /dev/null; then
   # DBNAME is in SID array
fi

This will fail if any of the entries in SID contain spaces, and other odd characters will undoubtedly cause problems as well.

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2 Comments

This can return a false positive, even if entries in SID contain no spaces, eg. if the user enters "mydb1 mydb2"
Follow up to this issue. I did further research and I believe it should be: if echo ${SID[@]} | grep -o "$DBNAME"; then echo "Match found" fi Not sure really. :-) The grep -wq "$DBNAME" and grep "\<$DBNAME\>" did not work for me. Again thanks for all the contributions!

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