mkdir -p instead of mkdir

ln -sfn source target instead of ln -s source target

rm -f example.txt instead of rm example.txt

Modifying a file

if ! grep -qF "/mnt/dev" /etc/fstab; then
  echo "/dev/sda1 /mnt/dev ext4 defaults 0 0" | sudo tee -a /etc/fstab
fi

Check if variable, file or dir exists
formatting a device
mounting a device

Only one same job at a time ?

My solution to deal with this is to bind an IPv6 localhost ::1 socket to a given port. Only one process can do this, and thus it’s a very effective mutex. No lock files to cause havoc, no dealing with the dark and buggy corners of advisory file locking.

For shell scripts, simply replace the #!/bin/sh with #!/somewhere/bin/lock 2048 where 2048 is the port number you will use to enforce the lock (greater than 1024 if you do not want to deal with the hassles of privileged ports).

Takeaways:

• It is possible to list a directory with 8 million files in it.
• strace is your friend
• Don't be afraid to compile code and modify it (hell, simple C compiles so fast it could be interpreted)
• There is no good reason to have 8 million files in a directory :-), but this was a good learning experience (and possibly a good interview question).

The last point is the most important :D

Do one thing per command and one only. Everything will be fine.

Yes 👍

😮

cat toto.txt | sort | uniq > pas-de-doublons.txt

to

cat toto.txt | awk '!x[$0]++' > pas-de-doublons.txt

Fun ! This respect the KISS principle 😄
Using the tool named souffle.

Using two clipboards: one main + one swap