Creating filename_$(date %Y-%m-%d) from systemd bash inline script

Question

I am trying to execute a systemd timer and would like to keep the output from the executed script in a file per date. Here is my ExecStart script in the .service file:

ExecStart=/bin/bash -c 'echo $(date +%Y-%m-%d) >> /home/username/test_output_$(date +%Y-%m-%d).log'

This creates the file but adds a "hash" instead of the month name:

~/test_output_2017-ea3c0c2dd56c499a93412641e41008db-01.log

The content is the same:

2017-ea3c0c2dd56c499a93412641e41008db-01

If I run /bin/bash -c 'echo $(date +%Y-%m-%d)' in the shell without passing it through systemd service, it works as expected. Prints: 2017-09-01.

Does %m stand for something else than a month number in the systemd environment?

Any idea how to set the systemd service to put the standard output from the script into a file with the current date? Expected result: test_output_2017-09-01.log

Thank you.

Shufu

did you tried `date +%Y-%m-%d` instead of $(date +%Y-%m-%d) ? – Kuhlmann

$(...) evaluates the command. Otherwise, if we omit it, it will print date +%Y-%m-%d as a string and nothing more. – Shufu

` ... ` its like $(...) .. called command substitution => gnu.org/software/bash/manual/html_node/… – Kuhlmann

Possible duplicate of Append date to filename in linux, Appending a current date from a variable to a filename, Adding timestamp to a filename with mv in BASH, etc. – Rabbinate

Answer 1

You'll need to escape the $ and % signs, by doubling them both in order to make this work.

As described here:

• https://github.com/systemd/systemd/issues/2146
• https://www.freedesktop.org/software/systemd/man/systemd.service.html#Command%20lines

To pass a literal dollar sign, use "$$"

ExecStart=/bin/bash -c 'echo $$(date +%%Y-%%m-%%d) >> /home/username/test_output_$$(date +%%Y-%%m-%%d).log'

Clobber