Learn to use Bash parameters:

• Create and move into a new directory: mkdir foo && cd "$_"

Get the size of a file: du -sh file.txt.

Want to clear your screen but typing clear is too much work? Use ctrl+L instead.

Reload your bash profile: source ~/.bash_profile.

Need to remove those odd Windows line endings? dos2unix is your friend.

Redirect STDERR: 2> /dev/null or 2>&1.

Want to cat line by line? paste -d, file1 file2

Need a random sample of lines from a file? shuf -n 10 will give you 10 lines. In Mac you need to use gshuf.

Find

Looking for non-zero files? find -maxdepth 1 -size +0

Want directories modified within the last 30 minutes? find . -type d -mmin -30

Want to run a script over each file of a certain name in a directory?

find ../blah-directory -name "*rules.txt" -print0 | 
  xargs -0 -I {} ./myscript.sh {} | tee all_output.tsv

Get Public IP

dig +short myip.opendns.com @resolver1.opendns.com

Put this in your bashrc:

alias wanip='dig +short myip.opendns.com @resolver1.opendns.com'

Moreutils

Checkout moreutils for some useful cli, e.g., sponge.

# stop using those pesky temp files.
cut -d, -f2 top_10k.txt | sponge top_10k.txt

Awk

Prepend text.

awk '{print "http://" $0;}' < top_10k.txt

jq

Prettify the JSON: cat example.json | jq '.' Get the number of elements cat example.json | jq 'length'