C Shell Scripting/Passwords
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This chapter shows an example script, a password generator.
Source code:
#!/bin/csh -f
#
# Human readable password generator
#
alias random "head -c 200 < /dev/random | uuencode -m - | tail -n+2 | sed 's/[^0-9]//g' | head -c 5"
# Random prefixes
set prefix = ( aero anti auto bi bio cine deca demo dyna eco ergo geo gyno hypo kilo \
mega tera mini duo an auto be counter de dis ex fore infra inter mal mis \
neo non out pan post pre pseudo semi super trans twi vice )
# Random suffixes
set suffix = ( dom ity ment sion ness ence er ist tion or ance ive en ic al able y ous \
ful ise ize ate ify fy ly )
# Vowel sounds
set vowels = ( a o e i u ou oo ae ea ie )
# Consonants
set consonants = ( r t p s d f g h j k l z x c v b n m qu th sw pl )
# Select random prefix
@ index = (`random` % $#prefix) + 1
set password = $prefix[$index]
# Select random suffix
@ index = (`random` % $#suffix) + 1
set password_suffix = $suffix[$index]
#Use 2 syllables = ~60 million combinations
set syllables = 2
set i = 0
while ( $i < $syllables )
# selecting random consonant
@ index = (`random` % $#consonants) + 1
set password = $password""$consonants[$index]
# selecting random vowel
@ index = (`random` % $#vowels) + 1
set password = $password""$vowels[$index]
@ i ++
end
# if suffix begin with vovel..add another consonant
foreach v ( $vowels )
if ($v == `echo $password_suffix | head -c 1` ) then
@ index = (`random` % $#consonants) + 1
set password = $password""$consonants[$index]
break
endif
end
# add suffix
set password = $password""$password_suffix
echo $password
exit 0
Lessons:
- C shell doesn't have an easy way to calculate a random number like Bourne shell.
- Backslashes are required to put statements are multiple lines.
- Arrays are base one.
- Extracting the first character of a string is not built-in and requires extra work.