cheat ba sheet

my personal cheat sheet for bash and related stuff

notice the lack of capitalization and punctuation? that's because it's all casual and not serious and stuff

chapter 0: what you should already know

cd, ls, mv, cp, mkdir, pwd, rm, cat, rmdir, touch, grep

linking files

symbolic link ln -s /path/to/file/that/exists /path/to/new/link

text/stream manipulation

strip the first 4 characters of each line (i.e. start on the 5th character):

cut -c 5- filename

get all the characters up to and including the 5th one: cut -c -5, get 3rd up to and including 15th: cut -c 3-15

follow the new lines being added to the file as it grows (e.g. logfiles):

tail -f filename

loops

numerical

for ((i = 0 ; i < 5 ; i++ )); do echo "$i"; done
0
1
2
3
4
for ((i = 0 ; i < 5 ; i++ )); do mkdir "year-202$i"; done

infinite

interruptible with ctrl+c

while :; do echo 'waiting'; sleep 1; done

while : is the same as while true

over filenames

all files/directories in current directory, non-recursive, leaves hidden files (dotfiles) untouched

for filename in *; do mv "${filename}" "${filename}-backup"; done

bash does not match dotfiles when globbing with *, however, this can be set with shopt -s dotglob and unset with shopt -u dotglob

to only do it for a single command you could

shopt -s dotglob; for filename in *; do mv "${filename}" "${filename}-backup"; done; shopt -u dotglob

for zsh use setopt

setopt GLOB_DOTS; for filename in *; do mv "${filename}" "${filename}-backup"; done; unsetopt GLOB_DOTS