Bash - How can I execute a variable

Question

I am reading a file with lines like:

folder=abc
name=xyz

For some lines line I would like set a variable e.g name=xyz corresponding to the line I have read.

Cutting it down, with name=xyz and folder=abc, I have tried:

while read -r line; do
    $line
    echo $name
done < /etc/testfile.conf

This gives an error message ./test: line 4: folder=abc: command not found etc.

I have tried "$line" and $($line) and it is the same. Is it possible to do what I whant?

I have succeeded by doing:

while read -r line; do
    if [[ "$line" == 'folder'* ]]; then
        folder="$(echo "$line" | cut -d'=' -f 2)"
    fi
    if [[ "$line" == 'name'* ]]; then
        name="$(echo "$line" | cut -d'=' -f 2)"
    fi
done < /etc/testfile.conf

but this seems messy

What do you want to execute? ./test: line 4: folder=abc: command not found means that there execution occurred, but failed, as there was no such an application. Really hard to tell what are you asking about. — Flash Thunder
– Flash Thunder, Commented Apr 21, 2019 at 7:40
You seem to be set up to discover eval, then (hopefully sooner than later) concluding that redefining your problem is probably better than actually using eval. — tripleee
– tripleee, Commented Apr 21, 2019 at 7:51
@Flash Thunder, I was trying to set the variable "folder" to "abc" — NickH
– NickH, Commented Apr 21, 2019 at 11:35
@oguz ismail, That does the trick for what I want and is easy to follow — NickH
– NickH, Commented Apr 21, 2019 at 11:38
@Poshi, Thanks, it looks like it works, but to my untrained eye, oguz ismail's solution seems easier to read. — NickH
– NickH, Commented Apr 21, 2019 at 11:38

oguz ismail · Accepted Answer · 2019-04-21 08:55:49Z

3

for your sample, declare is the safest option:

while read -r line; do
  declare "$line"
done

$ echo "$folder"
abc
$ echo "$name"
xyz

answered Apr 21, 2019 at 8:55

oguz ismail

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Comments

Poshi · Accepted Answer · 2019-04-21 08:04:11Z

1

Direct approach, use eval.

Different approach, try with source or .:

$ echo "$line"
folder=abc
$ . <(echo "$line")
$ echo "$folder"
abc

But probably the good answer will be to tackle the problem in a different way.

answered Apr 21, 2019 at 8:04

Poshi

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2 Comments

Eran Ben-Natan Over a year ago

eval is your friend

chepner Over a year ago

"With friends like this, who needs enemies?"

oguz ismail · Accepted Answer · 2019-04-21 14:12:38Z

0

You can clean up your approach a bit without resorting to eval.

while IFS="=" read -r name value; do
    case $name in
        folder) folder=$value ;;
        name) name=$value ;;
    esac
done < /etc/testfile.conf

edited Apr 21, 2019 at 14:12

oguz ismail

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answered Apr 21, 2019 at 13:33

chepner

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Comments

ctac_ · Accepted Answer · 2019-04-21 18:38:40Z

0

why not only source de file ?

$ . infile ; echo "$name"
xyz

answered Apr 21, 2019 at 18:38

ctac_

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1 Comment

NickH Over a year ago

The file is actually somewhat more complicated. Divided into sections with xml type tags, and I only want a couple of values from each section. Thanks

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