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Some resources to incorporate:

• apt-get & apt-cache commands: https://www.tecmint.com/useful-basic-commands-of-apt-get-and-apt-cache-for-package-management/

Key point of scripting using sudo: sudo breaks into parts, for e.g. in sudo echo blah >> grok.txt the sudo may not apply to grok.txt and if it is a protected file, there may be problems. Best to write scripts without sudo, and then run them with sudo. Applies automatically to the entire script.

Specific functions related:

Command	Description
... & eg. spyder &	returning to command line after launching an application launches spyder & returns to command line
# blah	single-line comment in bash script
: ' body '	multi-line comment in bash script NOTE: The space between : ' at the beginning of the comment is ESSENTIAL.

Nvidia GPU related

Command	Description
nvidia-smi	shows GPU and driver being used etc.
nvidia-smi -l 5	shows GPU usage updated every 5s in this case
lspci grep -i nvidia	Shows gpu info. lspci gets hardware info, is piped through grep and -i is --ignore-case

Writing to and reading from files

Command	Description
echo <text> >> <filepath>	APPENDS the text as a new line in the file
echo <text> > <filepath>	ERASES and ADDS the text as a fresh line in the file. BE CAREFUL with single > vs. double >>
echo 'deb blah blah...' | sudo tee --append /etc/apt/source.list	write using echo & tee to a file Especially useful when the destination is root contolled. sudo at the beginning doesn't apply after the pipe
sudo sh -c "echo 'something' >> /etc/privilegedfile"	can also be used to write to root privileged files Note: its like running a bash script from a command line interesting to check out how expansion of variables within " " and non-expansion within ' ' for echo can be managed with this
cat <filename>	displays contents of file in std out
more <filename>	displays contents of file in std out as a buffer within std out (any key to quit)
less <filename>	displays contents of file in separate buffer within terminal (like man command) (q to quit)

Operating system info related

Command	Description
lsb_release -a	shows all info about version of ubuntu on terminal
lsb_release -c	shows codename of ubuntu version on terminal, like xenial for 16.04
lsb_release -r	shows release no. of version of ubuntu on terminal, like 16.04
lsb_release -d	shows description of version of ubuntu on terminal, like Ubuntu 16.04.3 LTS

Symlinks

Command	Description
ln -s [path/to/target/directory] [path/to/symlink]	creates a symlink to the target directory at the specified path Note: The symlink name should not exist in advance, i.e. don't create a directory in advance. It will be created Note: There are no / at the end of the directory names - VERY IMPORTANT
ln -s [path/to/target/directory] [path/to/destination/directory]	A symlink to the target directory is created WITHIN the destination directory Note: The destination directory NEEDS to exist in advance. Needs to be created in advance Note: There are no / at the end of the directory names - VERY IMPORTANT
Think about it this way:	If the 2nd argument is a directory (i.e. an existing one), then symlink goes INSIDE it. If it is not a directory, then a symlink is created there for it.

Environment and env variables related

Command	Description
printenv	displays full environment with all env variables
'<ENV_VARIABLE> = env_variable_value'	sets the particular env variable (only for the session)
source ~/.bashrc	reload ~/.bashrc

Files and directories related

Command	Description
du -sh <dirpath/name>	shows size of directory
du -h <dirpath/name>	lists size of contents of directory

Search related

find: helps find files etc

Command	Description
find . maxdepth 1 -name "*string*" -print	searches current position recursively (folder can be specified for search) where the string is in the name of the file and prints it to stdout. Maxdepth, if not provided means recursively without limit.

grep: finds text in files (ag & rg are faster versions)

Package management related

(Additional install: dctrl-tools)

Command	Description
sudo apt install vs sudo apt-get install	apt installs without asking for confirmation. I.e., is equivalent to apt-get -y
sudo gdebi -n <package.deb> vs sudo dpkg -i <package.deb>	dpkg -i only "registers" the package (in /etc/apt/sources.list.d; where all info about apt package sources & ppas are) apt-get update & apt-get install then needs to be run. Does not pull in external dependencies if required. gdebi does. Therefore gdebi preferred.
apt show <package> can be grepped apt show | grep build	Show package details for apt repo Note: DOES NOT work with apt-get, just with apt <- This can show, for example, if build-essential is in the characterisctic, i.e. if it belongs to it.
apt-cache policy	View all ppas
apt-add-repository --remove <ppa> or after installing ppa-purge on apt sudo ppa-purge <ppa>	Remove ppas Note: Listing and removing done much more reliably from software-properties gui. Have had problems with both the above
apt list --installed <google\*>	Listing all installed packages. Can include any globbing pattern in < >
dpkg -l | grep -i <google\*>	Listing all installed packages. Even more effective than above
sudo apt-get remove <application>	Removes a package binaries, doesn't clean everything
sudo apt-get purge <application> OR sudo apt-get remove --purge <application>	Removes a package, and everything associated with it except config files in the home directory & dependencies
sudo apt-get autoremove	Removes all orphaned packages, not required after removing/purging
sudo apt-get --purge autoremove <packagename OR sudo apt-get purge --autoremove <packagename>	Removes all orphaned packages, not required after removing/purging
grep-dctrl -sPackage . /var/lib/apt/lists/ppa.launchpad.net_<repo>	Displays all packages that can be installed from that repo (ppa) /var/lib/apt/lists/ppa.launchpad.net is where all the ppa info is at
dpkg -L <package>	lists all files related to the package
dpkg -S <filename>	reverse of the above, provides name of package associated with that file
`apt-cache --no-all-versions show $package	grep '^Size: '`	shows size of an installed package (can be explored for what else apt-cache can show)

Processes/PID related

Command	Description
ps -e	list all processes ls lists files, ps lists processes, but needs -e flag
pgrep -nf "manage.py runserver" pgrep -nf "firefox"	To get the PID for a process with a particular string in the CMD that launched the process
ps -e | grep "firefox"	Does the same as above, piped through grep
ps -fp <PID>	To get the full name of a PID

wget

Command	Description
wget -r --no-parent <http://site.com	downloads all pages of site
wget -r --no-parent <http://site.com/songs/	downloads all pages of site under songs

Users & groups related

Command	Description
sudo usermod -aG <group> <user>	add user to group
sudo gpasswd -a <user> <group>	add user to group (using gpasswd)
sudo gpasswd -d <user> <group>	delete user from group (using gpasswd; delete much easier with gpasswd than with usermod)
sudo usermod -G "" <user>	removes user from all groups except their primary group
compgen -g	lists all groups
compgen -u	lists all users
sudo groupadd <group>	adds a group
groups <user>	list all groups user is in
getent group <groupname>	list all users in group