# Some reminders of semantics - http://linux.die.net/man/1/bash # Arithmetic expansion a=$((3 + 4)) ; echo $a b=$((a++ * 3)) ; echo $b # 21, a is now 8 # ~ bitwise negation, <<,>> bitwise shift, & ^ | bitwise and, xor, or z=${varName:-10} # use 10 if unset # ! no spaces before/after "=" (otherwise looks like a cmd) echo ${varName:=10} # use 10 if unset *and* set varName echo ${#var} # length of $var value v[2]=foo # indexed array w[bar]=baz # associative array echo arrays ${v[2]} ${w[bar]} # got to use braces v[3]=goo echo "${v[*]}" # one word echo "${v[@]}" # separate words echo ${!v[@]} # the keys v=$(date) # command substitution echo $# # num of params # Brace Expansion - generate arbitrary strings.... echo a{1,2,3}b # a1b a2b a3b echo 1.{1..9} # 1.1 1.2 1.3... echo {A..Z}{0..9} # A0 A1... B0 B1... ..Z9 # Conditional expressions [[ -a filenameExists ]] [[ -f regularFile ]] [[ -d directiryExists ]] [[ -s fileIsBiggerThanZero ]] [[ -z isThisStringZeroLength ]] [[ string1 -eq string2 ]] function aFunc() { echo $@ # args are avail automatically date printf "%6.3f\n" 2 # std printf } aFunc some args declare -f # list/show functions # interactive shells read from # /etc/profile, ~/.bash_profile, ~/.bash_login, ~/.profile # (when exiting, then reads from ~/.bash_logout, /etc/bash/bash.bash_logout) # non-interactive # file $BASH_ENV, echo $* echo "$*" # a single argument with all the args echo $@ echo "$@" # all the args singly echo $MACHTYPE echo $RANDOM echo $SECONDS # seconds since running of this shell