Notes from Command Line Course by Remy Sharp

Learn command line pipes, alias, zsh, string processing and more.

Written by Eva Dee on (about a 4 minute read).

List

  • ls -ltr

l = list, t = sort by time modified, r = reverse results

  • cd -

Go to the last directory - great for jumping between two directories.

  • which [application name]

Tells you where the app is running from.

Find and Pipe

  • find .

Print all the files in the current directory (including hidden files).

  • find . | grep .md

Find all markdown files.

  • find . | grep .md | wc -l

And count how many lines.

  • find . | grep .md | xargs cat | wc -w

How many words in each markdown file.

  • find [directory] -mtime -1 -ls

Find all files modified in the last 24 hours.

  • find [directory] -mtime -1 -ls | egrep .js$ | awk '{ print $1 }'

Find above, but only files ending in .js and print out the first column.

Grep

  • grep -n [term]

Will show the line number of where the match occurred.

  • grep -c [term]

Count the number of occurrences.

  • grep [term] -n -A 2 -B 2

Will print two lines before and two lines after the match.

  • grep '^#

Find all the headings in a markdown file.

Tail and Less

  • cat [file] | pbcopy

Copy the contents of a file onto the clipboard.

  • tail -f [file]

Follow the file stream (will continue to print newlines).

  • less

For file pagination:

  • b navigate backward
  • f navigate forward

👩‍💻 Make sure to always sort before using uniq (as it only works on neighboring lines).

  • egrep '^\s+RT @' freezing.log | sort | uniq -c | sort -nr | less

Using egrep to search for an expression starting with one or more spaces followed by RT @, sort the result, count the number of uniq ones, sort the result by reverse number and pipe into less for easier perusal 💪

  • vi /etc/sudoers

👩‍💻 see what sudo powers you have

chmod and chown that I didn't pay attention too (since I don't work in shared environments) 😬.

Managing processes

  • ps auxww | grep [term] -i

Show all running processes.

  • kill -9

Forced shutdown.

  • df -h

Disk space.

  • du -hs

Disk usage for a particular directory (human readable, summary number).

  • top /htop

  • uptime

For a quick overview (load averages).

Aliases

My git aliases:

  • ga='git add'
  • gcm='git checkout master'
  • gd='git diff'
  • gp='git push'
  • gf='git fetch'
  • gl='git pull'
  • gs='git-status'

Wget and Curl

  • wget [url]

Will save that page to your harddrive.

  • wget -r -l4 -spider -D [url]

Will recursively save all the pages (spider), 4 links deep, inside a specific domain.

  • wget ‐‐level=1 ‐‐recursive ‐‐no-parent ‐‐accept mp3,MP3 http://example.com/mp3/

Download all the MP3 files from a sub-directory

  • wget ‐‐mirror ‐‐domains=abc.com,files.abc.com,docs.abc.com ‐‐accept=pdf http://abc.com/

Download the PDF documents from a website through recursion but stay within specific domains.

  • curl [url] | scrape p

Would scrape all the p tags from that page.

  • curl -I [url]

Returns headers.

  • curl -L -I -X GET [url]

GET request, get all headers, following redirects.

👩‍💻 In browser developer tools, Networks tab, you can copy each request as Curl (and then run it locally).

Misc

Ngrok: will tunnel any local port into a public url.

  • cat [file.json] | json --keys

Will list out all the keys at root level.

  • json -a

Process array as an object which allows for lookups.

  • awk '{ print $2 }'

Split the string up by spaces and print the second column only ($0 represents the entire string).

  • ps auxww | grep node | awk '{ print $1 }'

Find all node processes.

  • ps auxww | grep node | awk '{ print $1 }' | xargs kill

Find them and destroy them! xargs takes the pipped in output and takes it as an argument for the next thing.

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