A few useful bash tricks

tricks.txt

Random useful bash stuff:
1. . ^foo^bar - bash !! but replaces the first occurrence of foo with bar
2. !!:/gs/foo/bar - bash !! but replaces all occurrences of foo with bar
3. cd -4 = cd; cd; cd; cd. cd -- = cd; cd. cd - = cd; pwd (or use pushd and popd)
4. diff <(sort a) <(sort b) The output of sort a is pushed into a pipe which pretends to be a file for diff. This is process substitution
5. < foo grep bar | sort  is the same as cat foo | grep bar | sort
6. $'\167' is the same as w - bash interprets octal! Also works with hex!
7. If you do echo !!:4 will echo the 4th argument of the last command. !$ is the last arg and !^ is the fist, !* is all.
8. !g will autocomplete to the last command run that began with g
9. set -o vi - enable vim bindings for bash
10. **/* is all files within all folders starting at .
11. shopt -s cmdhist multi-line commands will be stored in history as one command
12. escape . will insert the last argument from your last command
13. ls a?b will ls all 3 character files starting with a and ending with b.
14. !?foo?:p will print the last command that used foo
15. set completion-ignore-case on makes bash easier
16. Combinations of control, alt, and characters do a lot of stuff with auto complete.
17. % - stuff about jobs
18. $- flag options
19. $_ Current terminal
20. $* expands to a single string while  $@ expands to multiple arguments
21. cat << EOF and cat <<- EOF, etc are heredocs! Multi-line bash input without \s!
22. Bash variable expansion with substitution. ${FOO//Pattern/Replacement} Expand a variable while replacing certain characters in the expansion with others! (There are a dozen variations of this, like one that replaces only the first occurrence)
23. ls a[bc] will ls ab only if ab exists and ls ac only if ac exists
24. touch a{0..9} will touch 0... touch 9
25. FOO="a b"; echo c d ${FOO#a} prints c d b
26. &> is shorthand for 2>&1 > . Similarly |& and &>> are shorthand.
27. Adding a trailing space to an alias forces that alias to respect other aliases; e.x. alias x='xargs '; alias c=cat; echo a.c | x c works only with the trailing space
These are just some off the top of my head, feel free to add a few. Just thought they were worth sharing :slightly_smiling_face:

Also: https://www.gnu.org/software/bash/manual/html_node/Shell-Parameter-Expansion.html