paswdgen

#!/bin/bash
# random password generator by typedeaF
# This program has no "real" value other than introducing some bash concepts and putting them to use.
# to strip the comments: cat this.file | grep -v '^# '
 
 
# Sets the maximum size of the password the script will generate
MAXSIZE=50
 
# Holds valid password characters.
# Put the non alph-numeric in single quotes so the program knows that it is part of the array and not a seperate part of the program. 
# Example if the # is not in a set of single or double quotes it will comment out any part of the line after the # symbol and will not reconize the characters as part of the array.
array0=(
q w e r t y u i o p a s d f g h j k l z x c v b n m Q W E R T Y U I O P A S D F
G H J K L Z X C V B N M 1 2 3 4 5 6 7 8 9 0 '!' '@' '$' '%' '^' '&' '#' '*' '('
')' '+' '-' '=' '|' '/' '<' '>' '~' '`' ':' ';' '[' ']' '{' '}' '|' ',' '.' '?'
'_')
 
# Used in conjunction with modulus to keep random numbers in range of the array size
MODNUM=${#array0[*]}
 
# Keeps track of the number characters in the password we have generated
pwd_len=0
 
# Bash's command substitution syntax to store the results of the tput command
term_clear=$(tput clear)
 
# Stores the number of lines or rows on the terminal display
max_lines=$(tput lines)
 
# Stores the number of columns on the terminal display
max_cols=$(tput cols)
 
# Finds the appropriate spot to indent for horizontally centered output
indent=$(( ((max_cols / 2)) - ((MAXSIZE / 2)) ))
 
# Finds the vertical center of the terminal.
line_num=$(( max_lines / 2 ))
 
# Clear the screen
echo $term_clear
 
# The outer while loop starts at 0 and loops till MAXSIZE, creating a passwd char each iteration.
# The shells $RANDOM variable creates a semi-random unsigned number. This is our entropy. =x
# x simply holds some random unsigned int that will be used to make the character scramble.
# 500 was choosen for speed and nothing else. Leave out the mod 500 if you want or change it.
# The inner loop displays the password characters. Tput keeps the cursor in the proper position.
# Mod MODNUM keeps the random number inside the size of the array so it doesnt over index.
while [ $pwd_len -lt $MAXSIZE ]
do
  x=$(($RANDOM%500))
  y=0
  while [ $y -lt $x ]
  do
    ((y++))
    index=$(($RANDOM%$MODNUM))
    tput cup $line_num $(( indent + pwd_len ))
    echo -n "${array0[$index]}"
  done
  ((pwd_len++))
done
 
# Place the cursor at the bottom of the screen --where is usually at.
tput cup $max_lines 0
 
exit 0