Shell

eg. bash (sh but “bourne” again), zsh (default for macOS), tcsh (NIH favorite)

• https://www.tutorialspoint.com/unix/index.htm starts super super basic but covers advance topics (via Orma)
• https://seankross.com/the-unix-workbench/command-line-basics.html
• https://missing.csail.mit.edu/2020/shell-tools/ via Warren
• https://www.learnshell.org/ (via Amar)
• AFNI's unix intro to scripting
• Andy's brain blog book unix chapter includes videos
• Pitt's center for research computing suggests
  • https://cvw.cac.cornell.edu/Linux/default
  • https://software-carpentry.org/lessons/

https://readline.kablamo.org/emacs.html

fzf, fasd (z), readline editing options, alt+., ctrl+r, fuzzy ctrl+r, alt+n newfiles

short if-statements. short form function definitions. regexp w/BASH_REMATCH

if [ -r file.txt ]; then
  rm file.txt
fi
 
# same as
[ -r file.txt ] && rm file.txt
 
# same as
test -r file.txt && rm "$_"
 
####
 
function abc {
  echo abc
}
 
# same as
abc(){ echo abc; }
 
###
 
foobar="a1 b2 c3"
[[ $foobar =~ c.* ]] && echo $BASH_REMATCH # c3

Both functions and scripts take “input arguments”: what's provided to the right of the script or function.

“$#” is number input args, “$*” is all as single string “$@” is each argument quoted $1 .. $9 are input arguments 1 to 9 ¹⁾. printf like echo but first argument is how to format what follows

nargs()    { echo  "$#"; }
arg_at()   { nargs "$@"; }
arg_star() { nargs "$*"; }
 
arg_at   a b c # 3
arg_star a b c # 1
 
second()   { printf "*%s*\n" "$2"; }
arg_at2()  { second "$@"; }
arg_star2(){ second "$*"; }
 
arg_at2   a b c # *b*
arg_star2 a b c # **