easier way in bash?

[PGScooter]

Hi,

Suppose I have "'one', 'green', 'sevenkj'" in an array. Is there an easier way rather than one by one doing the following?



if [ "$aname" = 'one' ] || [ "$aname" = 'green' ] || [ "$aname" = 'sevenkj' ] || [ "$aname" = 'tricky' ] || [ "$aname" = 'slot' ] || [ "$aname" = 'fish' ] || [ "$aname" = 'flick' ] || [ "$aname" = 'plughome' ]; then


thanks!

[PhrankDaChickenGeek]

Try something along the lines of:



RESULT=$(echo $ARRAY | grep "$aname")
if [ "$RESULT" != "" ]; then

If $RESULT contains something, then $aname was found in the array. Otherwise $RESULT will = ""

[jpkotta]

You can also do something like:


#!/bin/bash

declare -a names
names=(one green sevenkj)

is_name_valid()
{
a_name="$1"
valid=0
for ((i = 0; i < ${#names}; i++)) ; do
if [[ "$a_name" = "${names[$i]}" ]] ; then
valid=1
break
fi
done
echo $valid
}

echo $(is_name_valid "foo")
echo $(is_name_valid "one")

Honestly, I like PhrankDaChickenGeek's better, but this way you don't need to run grep.

[PGScooter]

phrank and jpkotta,

thank you both for your help! phrank, that is a very creative and quick way.

jpkatta, are there any main reasons why I would not want to use grep? is it more reliable/faster to use simpler commands?

[Arndt]

phrank and jpkotta,

thank you both for your help! phrank, that is a very creative and quick way.

jpkatta, are there any main reasons why I would not want to use grep? is it more reliable/faster to use simpler commands?

Beware if one of the entries might match the other, for example if you have both "green" and "greenish". Anchoring the grep search (using ^ and $) may be enough to solve that problem.

[PGScooter]

Beware if one of the entries might match the other, for example if you have both "green" and "greenish". Anchoring the grep search (using ^ and $) may be enough to solve that problem.

ah, indeed I had not thought of that! thank you

[odyniec]

Here's another method -- no grep, just bash. Example of checking for an element that exists in the array:

$ array=(red green blue)
$ a=" ${array } "
$ aname=blue
$ [ "$a" == "${a/ $aname /}" ]
$ echo $?
1

And for one that doesn't exist in the array:

$ aname=yellow
$ [ "$a" == "${a/ $aname /}" ]
$ echo $?
0

[PGScooter]

odyniec,

would you mind explaining your code please? I do not understand the 2nd and 4th lines of your first code bracket. Thanks

[odyniec]

In this line:

a=" ${array } "
${array } expands to all elements of $array, separated by spaces. A space is also added at the beginning and at the end, making $a equal to " red green blue ". The added spaces are there to address the "green" vs. "greeninsh" issue that Arndt pointed out.


[ "$a" == "${a/ $aname /}" ]
${a/ $aname /} is a bash construct meaning: replace the first occurrence of " $aname " within $a with an empty string.

The whole command does a comparison of $a before and after the replacement. If the two are not equal ($? set to 1), it means there was a replacement, so obviously $aname must be in the array.

[jpkotta]

Beware if one of the entries might match the other, for example if you have both "green" and "greenish". Anchoring the grep search (using ^ and $) may be enough to solve that problem.

That's the main reason. Also, it may or may not be slower to call grep, depending on the size of your array and how often you check for membership.