Simple bash script for generating random passwords. We didn’t write this and don’t know exactly where it came from.
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#!/bin/bash MATRIX="0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz" LENGTH=$1 while [ "${n:=1}" -le "$LENGTH" ] # ==> Recall that := is "default substitution" operator. # ==> So, if 'n' has not been initialized, set it to 1. do PASS="$PASS${MATRIX:$(($RANDOM%${#MATRIX})):1}" # ==> Very clever, but tricky. # ==> Starting from the innermost nesting... # ==> ${#MATRIX} returns length of array MATRIX. # ==> $RANDOM%${#MATRIX} returns random number between 1 # ==> and [length of MATRIX] - 1. # ==> ${MATRIX:$(($RANDOM%${#MATRIX})):1} # ==> returns expansion of MATRIX at random position, by length 1. # ==> See {var:pos:len} parameter substitution in Chapter 9. # ==> and the associated examples. # ==> PASS=... simply pastes this result onto previous PASS (concatenation). # ==> To visualize this more clearly, uncomment the following line # echo "$PASS" # ==> to see PASS being built up, # ==> one character at a time, each iteration of the loop. let n+=1 # ==> Increment 'n' for next pass. done echo -n "$PASS" # ==> Or, redirect to a file, as desired. exit 0 |