The watch command is very useful, for those who don’t know, it starts an automated loop with a default of two seconds and executes whatever commands you place after it.

It allows you to actively monitor systems without having to manually re-run your command.

So for instance, if you wanted to see all storage block devices and monitor what a new storage device shows up as when you plug it in, you could do:

watch lsblk

And see in real time the drive mount. Technically not “real time” because the default refresh is 2 seconds, but you can specify shorter or longer intervals.

Obviously my example is kind of silly, but you can combine this with other commands or even whole bash scripts to do some cool stuff.

There are a lot of great commands in here, so here are my favorites that I haven’t seen yet:

• crontab -e
• && and || operators
• “>” and >> chevrons and input/output redirection
• for loops, while/if/then/else
• Basic scripts
• Stdin vs stdout vs /dev/null

Need to push a file out to a couple dozen workstations and then install it?

for i in $(cat /tmp/wks.txt); do echo $i; rsync -azvP /tmp/file $i:/opt/dir/; ssh -qo Connect timeout=5 $i “touch /dev/pee/pee”; done

Or script it using if else statements where you pull info from remote machines to see if an update is needed and then push the update if it’s out of date. And if it’s in a script file then you don’t have search through days of old history commands to find that one function.

Or just throw that script into crontab and automate it entirely.

I’m a big enjoyer of pushd and popd

so if youre in a working dir and need to go work in a different dir, you can pushd ./, cd to the new dir and do your thing, then popd to go back to the old dir without typing in the path again

find /path/to/starting/dir -type f -regextype egrep -regex 'some[[:space:]]*regex[[:space:]]*(goes|here)' -exec mv {} /path/to/new/directory/ \;

I routinely have to find a bunch of files that match a particular pattern and then do something with those files, and as a result, find with -exec is one of my top commands.

If you’re someone who doesn’t know wtf that above command does, here’s a breakdown piece by piece:

• find - cli tool to find files based on lots of different parameters
• /path/to/starting/dir - the directory at which find will start looking for files recursively moving down the file tree
• -type f - specifies I only want find to find files.
• -regextype egrep - In this example I’m using regex to pattern match filenames, and this tells find what flavor of regex to use
• -regex 'regex.here' - The regex to be used to pattern match against the filenames
• -exec - exec is a way to redirect output in bash and use that output as a parameter in the subsequent command.
• mv {} /path/to/new/directory/ - mv is just an example, you can use almost any command here. The important bit is {}, which is the placeholder for the parameter coming from find, in this case, a full file path. So this would read when expanded, mv /full/path/of/file/that/matches/the/regex.file /path/to/new/directory/
• \; - This terminates the command. The semi-colon is the actual termination, but it must be escaped so that the current shell doesn’t see it and try to use it as a command separator.

fabien@debian2080ti:~$ history  | sed 's/ ..... //' | sort | uniq -c | sort -n | tail
# with parameters
     13 cd Prototypes/
     14 adb disconnect; cd ~/Downloads/Shows/ ; adb connect videoprojector ;
     14 cd ..
     21 s # alias s='ssh shell -t "screen -raAD"'
     36 node .
     36 ./todo 
     42 vi index.js 
     42 vi todo # which I use as metadata or starting script in ~/Prototypes
     44 ls
    105 lr # alias lr="ls -lrth"
fabien@debian2080ti:~$ history  | sed 's/ ..... //' | sed 's/ .*//' | sort | uniq -c | sort -n | tail
# without parameters
     35 rm
     36 node
     36 ./todo
     39 git
     39 mv
     70 ls
     71 adb
     96 cd
    110 lr
    118 vi

Search for github repos of dotfiles and read through people’s shell profiles, aliases, and functions. You’ll learn a lot.

I use $_ a lot, it allows you to use the last parameter of the previous command in your current command

mkdir something && cd $_

nano file
chmod +x $_

As a simple example.

If you want to create nested folders, you can do it in one go by adding -p to mkdir

mkdir -p bunch/of/nested/folders

Good explanation here:
https://koenwoortman.com/bash-mkdir-multiple-subdirectories/q

Sometimes starting a service takes a while and you’re sitting there waiting for the terminal to be available again. Just add --no-block to systemctl and it will do it on the background without keeping the terminal occupied.

systemctl start --no-block myservice

ps -ef | grep <process_name

Kill -9 proces id

I googled that -15 is better, I forgot what -9 even did, been using it for years.

ctrl+r on bash will let you quickly search and execute previous commands by typing the first few characters usually.

it’s much more of a game changer than it first meets the eye.

Not a command but the tab key for auto complete. This made it much easier for me.

ripgrep

parallel, easy multithreading right in the command line. This is what I wish was included in every programming language’s standard library, a dead simple parallelization function that takes a collection, an operation to be performed on the members of that collection, and optionally the max number of threads (should be the number of hardware threads available on the system by default), and just does it without needing to manually set up threads and handlers.

inotifywait, for seeing what files are being accessed/modified.

tail -F, for a live feed of a log file.

script, for recording a terminal session complete with control and formatting characters and your inputs. You can then cat the generated file to get the exact output back in your terminal.

screen, starts a terminal session that keeps running after you close the window/SSH and can be re-accessed with screen -x.

Finally, a more complex command I often find myself repeatedly hitting the up arrow to get:

find . -type f -name '*' -print0 | parallel --null 'echo {}'

Recursively lists every file in the current directory and uses parallel to perform some operation on them. The {} in the parallel string will be replaced with the path to a given file. The '*' part can be replaced with a more specific filter for the file name, like '*.txt'.

when I forget to include sudo in my command:

sudo !!

nc is useful. For example: if you have a disk image downloaded on computer A but want to write it to an SD card on computer B, you can run something like

user@B: nc -l 1234 | pv > /dev/$sdcard

And

user@A: nc B.local 1234 < /path/to/image.img

(I may have syntax messed up–also don’t transfer sensitive information this way!)

Similarly, no need to store a compressed file if you’re going to uncompress it as soon as you download it—just pipe wget or curl to tar or xz or whatever.

I once burnt a CD of a Linux ISO by wgeting directly to cdrecord. It was actually kinda useful because it was on a laptop that was running out of HD space. Luckily the University Internet was fast and the CD was successfully burnt :)