Unix

http://robin.me/pi.html


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Redirecting bash script output to syslog

exec 1> >(logger -s -t $(basename $0)) 2>&1

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command line replacement:
$ !!:s/102/1002



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lolcat - colourful text
figlet - large characters
asciiquarium - text aquarium 
cowsay - cows? 




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disk usage:
ncdu 

matrix effect:
cmatrix

head -n 2 < list1 > list2 
will read from list1, passing it to head to take the first two lines, 
then putting these in a file called list2. Add in a pipe: 
sort < list1 | uniq > list3 
 
export PS1="[\$(date +%k:%M:%S)]\u@\h \w> " 
 
clear

~. kills current ssh session
 
tar zxvf Rpi.GPIO-0.4.1a.tar.gz 
 
sudo dd if=~/Downloads/2015-05-05-wheezy-raspbian.img 
of=/dev/sdb bs=1M 
 
Use sudo fdisk -l both 
before and after plugging in the SD card (you can also use df to see what’s 
mounted). If, say, a /dev/sdb appears, with the size equal to the SD card, 
then unmount with umount /dev/sdb1. Now copy the disk image with 

perl script to replace tabs with spaces
perl -pi.old -e 's{\t+}{ }g' file.txt

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# m h  dom mon dow   command
# * * * * *  command to execute
# ┬ ┬ ┬ ┬ ┬
# │ │ │ │ │
# │ │ │ │ │
# │ │ │ │ └───── day of week (0 - 7) (0 to 6 are Sunday to Saturday, or use names; 7 is Sunday, the same as 0)
# │ │ │ └────────── month (1 - 12)
# │ │ └─────────────── day of month (1 - 31)
# │ └──────────────────── hour (0 - 23)
# └───────────────────────── min (0 - 59)
For example:

0 0 * * *  /home/pi/backup.sh

@reboot python /home/pi/myscript.py &




cd - ( previous directory )

ctrl l ( clear screen )

pushd /var
popd

ctrl z
fg

command !! ( appends command to the beginning of the last command )

ctrl r ( searches for previous command )

which python ( shows the directory of the app python )

History
!102 ( repeat command 102 )
ctrl u ( delete everything on line )

ctrl a ( goto beginning of line )
ctrl e ( goto end of line )

chain ; commands && only after successful completion

tail -f /var/log/syslog ( live tail )

truncate -s 0 hello.txt ( reduce everything in the file but keep the file )

ls | column -t ( puts data into columns )