Popular Linux Commands FCC

⬅️ Bash

• 🔗 From this FCC Video

History

• what we know of as Linux is actually a combo of GNU(the OS) and Linux (the Kernel)
• Linux is not Unix, but Unix-like. To be truly Unix you have to pay a lot of 💰 to get registered (also 🙅‍♀️ against the ethos of open and free)

Shell

• a computer interface to an OS
• the shell takes our commands and gives them to the OS to perform
• it’s named shell because it’s the outer layer of the OS
• terminal: a program that runs a shell
• absolute paths (start with ~): ~/Documents/...

mkdir

• mkdir -p create if it doesn’t exist yet (used when creating nested dirs)
• mkdir -p greenhouse/winter/lettuce

mv

• move the folder my_dir one level up: mv my_dir/ ../

head and tail

• by default output first 10 lines, if you want to change that: head -n 100
• tail -f to track a log

cat

• to add line number cat -n

sort

• sort things numerically sort -n
• in reverse order sort -r
• unique values only sort -u

uniq

• has more options than sort -u, e.g. you can print only duplicate lines, or only the lines that aren’t duplicate, uniq -d, uniq -u
• count the number of occurrences: uniq -c

expansion

• echo ~ (~ expands to your home directory)
• echo * a list of every pathway in the current folder
• echo *.txt narrows it down!
• ? matches any single character, ?? for two chars etc
• {} for curly brace expansion
• echo {1..99}
• the shell intervenes and expands a short thing into a longer thing

diff

• diff -y to see the files side by side for comparison
• diff -u to give you some context around each change (it’s what gif diff uses)

find

• find <LOCATION> <FILTER>
• -name -type -size -mtime
• -iname for case insensitive
• find . -type f -mtime 3 search files edited more than 3 days ago
• -exec specify the command you want find to execute on each item found
• find . -type f -exec cat {} \; execute cat, {} expands to the found file name \; to inform the terminal when the command ends

grep

• grep for searching inside the files
• greep <text> <filename>
• -n with line numbers
• -C with context, grep -nC 2 two lines before and after
• -r for recursive
• -i case insensitive
• works with regex

du

• for file and directory sizes
• -h human readable sizes
• find the largest dir on your desktopL du -h | sort -h

df

• information about the mounted file systems

history

• run a command from your history from a specific line: !<line number>
• find a command you ran a long time ago: history | grep '<word>'

ps

• inspect processes
• ps only user initiated process
• ps ax all processes
• ps axww to enable word wrap
• ps axww | grep 'Visual Studio Code'

top

• show top memory intensive processes
• top -o mem sort by memory used

kill

• 15 shut things down gracefully (default option)
• 9 shut things down forcefully
• kill -9 <PID>
• killall -9 node to kill all processes that match the name

xargs

• command1 | xargs command2 (the output of the first command becomes the input of the 2nd command, aka the command’s arguments)
• not all commands accept arguments from standard input (sort does)
• so xargs solved that, e.g. rm expects arguments after, but you can do | xargs rm…

ln

• ln -s for creating soft/symbolic links
• ln -s original.txt symlink.txt
• the change is propagated both ways, but if you delete the original file the symlink file will break
• links are good for running different versions of a program (does nvm use that? 🤔)