Timestamp in Exec= line of .desktop file possible?

Question

Lubuntu 16.04 - Openbox session

I can use the terminal to open a time-stamped file with gedit:

gedit ~/$(date +%Y%m%d%H%M%S).txt

The command can also be used via a keyboard shortcut in Openbox.

<keybind key="W-4">        # gedit time-stamped file
  <action name="Execute"><command>sh -c 'gedit ~/$(date +%Y%m%d%H%M%S).txt'</command></action>
</keybind>

But I can't do the same via the Exec= line of a .desktop file.

Exec=sh -c 'gedit ~/$(date +%Y%m%d%H%M%S).txt'

just creates a file called ~/.txt

So how do I get a .desktop file to do what I want?

Answer 1

Unfortunately, .desktop files don't always call sub-shell $() commands the way we would like them to. One way to do this that I have found would be to create another script that contains the sub-shell command to open the file like that.

The Exec line would look like:

Exec=/path/to/script

then your script file would contain the command to open your new file:

#!/bin/sh

gedit ~/$(date +%Y%m%d%H%M%S).txt

the script would also have to be executable:

chmod +x /path/to/script

Hope this helps!

Answer 2

The issue

A script is not necessary.

The issue is not that a .desktop file cannot run commands with subshells, since

Exec=/bin/bash -c "echo $(date) > ~/out.txt"

works perfectly fine in a .desktop file.

Fiddling around with the command, I came to the conclusion that the % -character is causing the issue. I have no explanation for it though, and so far I could not find information on how to solve or escape that.

I therefore went looking for a command to get the time without using the suspected character.

Alternatively use Ruby for the date & time

This lead me to Ruby, which produces the current date & time from the command:

$ ruby -e 'puts Time.now.inspect'
2016-05-29 16:12:36 +0200

When we edit the output a bit with awk, removing spaces and delimiters, we have just what we want, and a working command in the .desktop file, since we don't use %:

Exec=/bin/bash -c  "gedit ~/$(ruby -e 'puts Time.now.inspect' | awk -F'[: -]' '{print $1$2$3$4$5$6}')"

Note!

No doubt, the command can be "charmed up" a bit, I will probably edit the answer a bit today or tomorrow.

Answer 3

Since this is first google result, let me link another answer that is way simpler:

.desktop file with date variable not working

In short: 'The freedesktop standard specifies that filetype arguments use % symbol, but can be escaped via double % sign.'

So instead of

Exec=gedit ~/$(date +%Y%m%d%H%M%S).txt

use

Exec=gedit ~/$(date +%%Y%%m%%d%%H%%M%%S).txt