# linux tips
* `info coreutils`
* try to open manual pages for programs or configuration files you want to learn about. example: man locale.conf
* keybindings on the terminal
  * ctrl+l clear screen
  * ctrl+c quit process, sends the sigint signal
  * ctrl+d exit
* for ensuring permissions one may create, and regularly run, a script where the desired filesystem permissions are applied with commands like chmod. unanticipated permission changes are otherwise unlikely to be noticed
* [software list](/foreign/software-list.html)

## reading live updates from logfiles and other text files
tail -f displays lines from the end of files and continues to display live future updates - so you can wait and see updates in real-time
~~~
tail -f /var/log/mylogfile
~~~
-n specifies the number of last lines to show at first
~~~
tail -n 400 -f /var/log/mylogfile
~~~
it can be filtered
~~~
tail -f |grep myfilterstring
~~~
live updates of multiple files:
~~~
tail -f /var/log/mylogfile /var/log/another-file /var/log/and-another-file
~~~

## regular task execution, task scheduling with cron
### cron configuration format
see  [here](http://en.wikipedia.org/wiki/Cron#Format)

### example line

    0 */12 * * * /usr/bin/redmine-update-repositories

* "*" means "every". so that "* 3" would mean "every minute at hour 3"
* "*/2" means "each 2"

### installation of dcron
~~~
su root
# dcron is one of the simpler implementations
pacman -S dcron
systemctl enable crond
# remove the included preset jobs and directories - /etc/cron.daily and the like
crontab -d && rmdir /etc/cron*
mkdir /etc/cron.d
# create rules in cron job files
nano /etc/cron.d/myscript
systemctl start crond
~~~
crond sends the standard output from jobs per mail. you may not want this, so edit "/etc/conf.d/crond" and add "-m off" to the arguments.
"systemctl status crond" shows log and error information