Simple reminders
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# 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
Bash
INFO