Question

I’m trying to execute a command for each line coming from a cat command. I’m basing this on sample code I got from a vendor.

Here’s the script:

for tbl in 'cat /tmp/tables'
do
   echo $tbl
done

So I was expecting the output to be each line in the file. Instead I’m getting this:

cat
/tmp/tables

That’s obviously not what I wanted.

I’m going to replace the echo with an actual command that interfaces with a database.

Any help in straightening this out would be greatly appreciated.

Answer 1

You are using the wrong type of quotes.

You need to use the back-quotes rather than the single quote to make the argument being a program running and piping out the content to the forloop.

for tbl in `cat /tmp/tables` 
do 
    echo "$tbl"
done

Also for better readability (if you are using bash), you can write it as

for tbl in $(cat /tmp/tables) 
do 
    echo "$tbl"
done

If your expectations are to get each line (The for-loops above will give you each word), then you may be better off using xargs, like this

cat /tmp/tables | xargs -L1 echo

or as a loop

cat /tmp/tables | while read line; do echo "$line"; done