crunch - wordlist generator

// basic
// $ crunch [options]

$ crunch 4 4 1234 -o numbers.txt

// split

$ crunch 8 8 0123456789ABCDEF -b 2gb -o START  # 2gb per file
$ crunch 6 6 0123456789 -c 200000 -o START  # 200000 lines

// with specific pattern
-t 
@ -- lower case alpha characters
, -- upper case alhpa characters
% -- numeric characters
^ -- special characters (including space)

$ crunch 4 4 1234 -t @11@
1111
1112
1113
1114
2111
2112
2113
2114
3111
3112
3113
3114
4111
4112
4113
4114

// use pre-define charset

$ crunch 6 6 -f charset.lst ualpha

// string permutations

$ crunch 1 1 -p abc
abc
acb
bac
bca
cab
cba

// stop when specifies string

$ crunch 4 4 1234 -e 4411

Reference :
crunch - wordlist generator | Free software downloads at SourceForge.net
Creating Wordlists With Crunch | Penetration Testing Lab
A day with Tape: Creating wordlists with crunch v3.0