Extracting a line identified by special character '*' and storing it in a variable

Question

On Lubuntu 16.02, this command shows information about all desktops:

$ wmctrl -d
0  - DG: 3926x1600  VP: 0,0  WA: 0,24 2560x1576  desktop 1
1  - DG: 3926x1600  VP: 0,0  WA: 0,24 2560x1576  desktop 2
2  * DG: 3926x1600  VP: 0,0  WA: 0,24 2560x1576  desktop 3
3  - DG: 3926x1600  VP: 0,0  WA: 0,24 2560x1576  desktop 4
4  - DG: 3926x1600  VP: 0,0  WA: 0,24 2560x1576  desktop 5

Need to store and process the information about the active desktop, what shows up by:

$ wmctrl -d | grep "*"
2  * DG: 3926x1600  VP: 0,0  WA: 0,24 2560x1576  desktop 3

For some strange reason, this solution won't store the information needed:

$ activedesktop=$(wmctrl -d | grep "*")
$ echo $activedesktop
2 Desktop Documents Downloads Mail Music Pictures Public Videos DG: 3926x1600 VP: 0,0 WA: 0,24 2560x1576 desktop 3

As the variable inserts the home directories names where the "*" was supposed to be.

Why is this happening, and how to solve it?

Escape the `*`. Or use `grep "[*]"`. Also, see [matching a line with a literal asterisk “*” in grep](https://stackoverflow.com/questions/1581307/matching-a-line-with-a-literal-asterisk-in-grep) — Wiktor Stribiżew, Aug 03 '17 at 14:20
@WiktorStribiżew `activedesktop=$(wmctrl -d | grep "\*")` and `activedesktop=$(wmctrl -d | grep "[*]")` raise the same (wrong) result... — nightcod3r, Aug 03 '17 at 14:22
@melpomene gosh! I see it was replacing the asterisk in the second place... — nightcod3r, Aug 03 '17 at 14:26
Not the cause, but I recommend `fgrep` (or GNU `grep -F`) to match a fixed pattern instead of regexp. — Toby Speight, Aug 03 '17 at 16:23

score 1 · Answer 1 · answered Aug 03 '17 at 14:35

1

As pointed out by @melpomene, the variable does store the information needed, but the former echo interprets the asterisk.

So, the solution is just to double-quote the variable as in echo "$activedesktop".

answered Aug 03 '17 at 14:35

nightcod3r

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Extracting a line identified by special character '*' and storing it in a variable

1 Answers1