===== bash: "How To" ... utilize string substitutions =====
^  string parameter substitution  ^^^^^
^operation^what^code^example using:\\ export TST='abcabcaa'^result from\\ (abcabcaa)^
|remove|first occurrence of substring '__xyz__' in string|STR=${STR/'__xyz__'}|echo ${TST/'bc'}|aabcaa\\  (a<del>bc</del>abcaa)|
|:::|substring '__xyz__' everywhere in string|STR=${STR<nowiki>//</nowiki>'__xyz__'}|echo ${TST<nowiki>//</nowiki>'bc'}|aaaa\\  (a<del>bc</del>a<del>bc</del>aa)|
|:::|substring '__xyz__' at very beginning of string (prefix)|STR=${STR#'__xyz__'}|echo ${TST#'abca'}|bcaa\\  (<del>abca</del>bcaa)|
|:::|substring '__xyz__' at very end of string (suffix)|STR=${STR%__xyz__}|echo ${TST%'bcaa'}|abca\\  (abca<del>bcaa</del>)|
|:::|first __n__ characters|STR=${STR:__n__}|echo ${TST:2}|cabcaa\\  (<del>ab</del>cabcaa)|
|:::|last __n__ characters|STR=${STR:-__n__}|echo ${TST::-3}|abcab\\  (abcab<del>caa</del>)|
|extract|all characters after (!) position __n__\\ //(first char position: __n__=0)//|STR=${STR:__n__}|echo ${TST:1}|bcabcaa\\  (<del>a</del>bcabcaa)|
|:::|__m__ characters after (!) position __n__|STR=${STR:__n__:__m__}|echo ${TST:1:5}|bcabc\\  (<del>a</del>bcabc<del>aa</del>)|
|:::|characters after (!) position __n__ until end of string minus __m__|STR=${STR:__n__:-__m__}|echo ${TST:1:-1}|bcabca\\  (<del>a</del>bcabca<del>a</del>)|
|convert|to upper case|STR=${STR<nowiki>^^</nowiki>}|echo ${TST<nowiki>^^</nowiki>}|ABCABCAA|
|:::|to lower case|STR=${STR,,}|echo ${TST,,}|abcabcaa|
|cut|from begin of string to first end of substring '__xyz__'|STR=${STR#*'__xyz__'}|echo ${TST#*'bc'}|abcaa\\  (<del>abc</del>abcaa)|
|:::|from begin of string to last end of substring '__xyz__'|STR=${STR##*'__xyz__'}|echo ${TST##*'bc'}|aa\\  (<del>abcabc</del>aa)|
|:::|from last occurrence of substring '__xyz__' to end of string|STR=${STR%'__xyz__'*}|echo ${TST%'bc'*}|abca\\  (abca<del>bcaa</del>)|
|:::|from first occurrence of substring '__xyz__' to end of string|<nowiki>STR=${STR%%</nowiki>'__xyz__'*}|<nowiki>echo ${TST%%</nowiki>'c'*}|ab\\  (ab<del>cabcaa</del>)|

//work in progress//