Shell

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

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

“$#” is number input args, “$*” 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 # **