Bash string compare cannot match

Question

I want to filter some collections in mongodb to export. But the string compare seems incorrect.

$1 in my case is localhost:17017/mydb

shop is one of the collections in mongodb, but $i == 'shop' never succeed.

#!/bin/bash

colls=`mongo $1 --eval 'db.getCollectionNames();' | tail -1`

IFS=',' read -ra ADDR <<< $colls

for i in "${ADDR[@]}"
do
    if [[ $i == 'shop' ]]
    then
        echo $i
    fi
done

Or is there any other methods to export specified collections from mongodb?

are you trying to match "shop" or "'shop'"? if you need a partial match you can do case "$i" in *shop*)echo $i;;esac ... note the double quotes around $i, in case of odd characters — technosaurus
– technosaurus, Commented Aug 14, 2013 at 8:03

konsolebox · Accepted Answer · 2013-08-14 05:44:56Z

1

Try to echo the values you got and see perhaps how you should actually use the patterns. Also please quote your variables properly. It's also better to use $() over backticks:

#!/bin/bash

colls=$(mongo "$1" --eval 'db.getCollectionNames();' | tail -1)
echo "colls: $colls"

IFS=',' read -ra ADDR <<< "$colls"
echo "colls count: ${#ADDR[@]}"

for i in "${ADDR[@]}"
do
    echo "Trying |$i|."
    if [[ $i == 'shop' ]]
    then
        echo "$i"
    fi
done

edited Aug 14, 2013 at 5:44

answered Aug 14, 2013 at 4:58

konsolebox

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1 Comment

konsolebox Over a year ago

Somehow it prevents the contents of $colls from being re-evaluated with values of IFS before input.

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