Posted in Linux commands

Make temporary Files or directories

Sometimes I need a temporary file or a temporary directory with a unique name in my scripts. Of course I can create a file in /tmp with the actual time in its name. But what if some other user has the same idea, and the scripts run at the same time? Here comes mktemp.

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Posted in Linux commands

ssh Keys

ssh and scp are the usual programs to login to a remote host and to copy files from or to a remote host. Normally users just start the program and type their password. But this is not very convenient, and even impossible, if these programs are used in a script which has to run automatically, e.g. as a cron job.
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Posted in Linux commands

systemd, Part I

For my sensor network I run a server process, which collects the data from several sensors. This is a sort of a daemon. In a first version it was started in a crontab with the time “@reboot”. But during the development I had to restart it every now and then: search the PID, kill it, start it in the background.

Isn’t there a better way? systemd to the rescue. In this first systemd post I will install a service file, so that the process can be started and stopped from the root account.

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Posted in bash

Changing directories

Everyone knows the command cd – everyone uses it several times a day. (OK – not everyone, but every Linux user.) Most of us know, that we can change back to the last directory with

$ cd -

E.g.:

$ pwd
/home/maker/docs/sensors
$ cd /opt/sensors/bmp280
$ pwd
/opt/sensors/bmp280
$ cd -
$ pwd
/home/maker/docs/sensors

But what if you cd in your project directory and then need to change back into your docs directory? You have to type the whole path. Or do you?

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