notes/os/shells/zsh/zsh-script-vars.txt

cat -v /proc/$$/environ
	List env vars of current shell ($$ is for pid). -v - is for displaying zero-chars.


set -A arr one two three
arr=( one two three )
	Set an arr array-variable.
src_files=( **/*.[ch] )
	You can yse any form of subsitution for array also
	Note: for bash - use src_files=( $(find . -name '*.[ch]' -print) ).

declare (typeset is also possible instead of declare) - Assign attributes to vars.
	-a - arrray.
	-A - associated array (hash).
		declare -A people = (name1 val1 name2 val2 name3 val3)
	-p - print...
	-U - make unique (path/PATH - path is a companion array).
	-T LD_LIBRARY_PATH ld_library_path
		Tie -//- in the same way (tied arrays).
	-u - uppercase.
	-l - lowercase.
	-R <num> - right justification.
	-L <num> - left justification.
	-x - the same as "export" command.
	-r - readonly.
	-i - integer variable (integer <var> can also be used).
	-i optional_base - -//- for specifying base.
	-F - floating variable (float <var> can also be used).
	-E - -//- scientific.
	Note: f='1.0/3' - specify how many significant digit is needed (3).


echo ${#arr}
3
	Get the number of elements in the array.
echo ${arr[3]}
echo $arr[1]
	Array element access (index is 1-based in zsh, but 0-based in bash).
echo $arr
	Echo just the first element of arr in case of ksh and ALL the elements for zsh.
arr[2,3] = ( zwei drei )
	Replace a range of elements.
arr[2] = ()
	Delete the second element.
echo $arr[2,-1]
	Here -1 indicates the last element.

!!! Word-splitting is disabled in zsh by default !!!

var='one two'
showargs $=var
>>one<<
>>two<<
	Directly specify splitting a variable.

${arr[@]}
	Expand array elements. Each one is a separate word.
${arr[*]}
	Join all the elements to the string, separated by space.

Numbers:

echo $(( 3*4 ))
	Integer expression calculation.
echo $(( 0xff ))
echo $(( [#16] 255 ))
	For hexadecimal numbers.
echo $(( 12#193 ))
	For arbitrary base.
echo $(( 1. / 3 ))
	For floating-point output (0.3333333).


Alternative and default values:
echo ${var:-default}
	Specify default value in case if the variable is unset.
echo ${var:+alternative}
	Do the opposite (... if variable is set).

Variable patterns:

${var#pattern}, ${var##pattern}
	Expand var removing text that matches pattern (the least/most possible text) from the left.
${var%pattern}, ${var%%pattern}
	from the right.
${var//pattern/string}
	This does not enable greedy patterns.
	Note: to disable greedy pattern matching which is on by default, use (S) var-expansion flag.
$a[3,5]
	Extract substring from 3 to 5 symbol. Indices can be math-expressions.


Nested Expansion:
${${file##*/}%.$}
	Accept a file name and remove an initial path and file extension.

Variable expansion flags:
${(<flag>var}, where <flag> is one of the following:

L, U, C - Lower/Upper/Capitalize-First-Letter case.
a, i    - Array-Index/Case-Independent order.
o, O    - Ascending/Descending order.
f, s, z - Split at Lines/Specified-Char/Into-Words-Taking-Shell-Quoting-Into-Account.
F, j    - Join words using Newlines/Specified-Character.
c, w, W - Count Characters/Words/Words-Including-Empty-Ones.
Q       - Remove one level of quoting.
q       - Quote the resulting words.
V       - Make special characters visible.
l, r    - Pad words on the Left/Right.
t, k, v - Return the Type/Associative-Array-Keys/Associative-Array-Values of variable.
%, e    - Perform Prompt/Shell expansion of the value.
P       - Reinterpret values as a further variable name.

Example:
echo ${(ops:\n:)"$(cut -d: -f5 /etc/passwd)"}
echo ${(of)"$(cut -d: -f5 /etc/passwd)"}
	Here s flag define separator char (\n), 

Matching patterns against arrays:
${arr:#pattern}
	Each array element is matched against pattern and those that match are discarded.
${(M}arr:#pattern}
	Do the opposite - return only those elements that are matched.

echo ${(k)assoc_array}
	extract keys of associated array:
echo $assoc_array
echo ${(v)assoc_array}
	extract values of associated array:
echo ${(kv)assoc_array}
	extract keys/values of associated array:
assoc_array+=( key4 val4 ... )
	add other key/value pairs.
unset 'assoc_array[keyN]'
	remove a key/value.
echo ${(k)assoc_array[(r)val]}
	reverse lookup a single match.
echo ${(k)assoc_array[(R)val]}
	to reverse lookup all matches.
echo ${(v)assoc_array[(i)pattern}
	(i) allows us to use a pattern-match.


Loading files to vars:
input="$(cat config.ini)"
input="$(<config.ini)"
	The equiv forms.

while read; do
	echo $REPLY
done < config.ini
	Read one line at a time.

ps | while read; do
	echo $REPLY
done

ps | while read pid tty time cmd; do
	echo $cmd $pid
done
	The same, but using word-splitting.

while IFS=: read user pw uid gid name home shell; do
	echo $user $name
done </etc/passwd
	... Using internal field separator (IFS) var, changed locally.
	




zsh options

ksh_arrays
	To make 0-based array element index access.
octal_zeroes
	Enable octal zeroes.
c_bases
	Output standard c-convension bases.


zsh modules

zmodload zsh/mathfunc
	Load math functions (pi, atan, ...).