REX Grep

rexgrep is a program for matching and searching strings in files using the REX library. It is intended as a front end for the REX library and provides some command line switches to help using the REX library. For example rexgrep can display the generated Deterministic Finite Automata (DFA) or Non-Deterministic Finite Automata (NFA) from a regular expression.

Example 1 - Display DFA:

# rexgrep -e "hel+o" -D
State 0 ():  REX_STATETYPE_DEAD 
    [0x0 - 0xFFFFFFFF]                  -> 0

State 1 ():  REX_STATETYPE_START 
    [0x0 - 0x67]                        -> 0
    'h'                                 -> 2
    [0x69 - 0xFFFFFFFF]                 -> 0

State 2 (): 
    [0x0 - 0x64]                        -> 0
    'e'                                 -> 3
    [0x66 - 0xFFFFFFFF]                 -> 0

State 3 (): 
    [0x0 - 0x6B]                        -> 0
    'l'                                 -> 4
    [0x6D - 0xFFFFFFFF]                 -> 0

State 4 (): 
    [0x0 - 0x6B]                        -> 0
    'l'                                 -> 4
    [m - n]                             -> 0
    'o'                                 -> 5
    [0x70 - 0xFFFFFFFF]                 -> 0

State 5 ():  REX_STATETYPE_ACCEPT  (5*)
    [0x0 - 0xFFFFFFFF]                  -> 0

Example 2 - Display NFA. Note: if the regular expression characters are not ASCII, their hex value will be displayed. Wide characters are encoded within the state the same way as ASCII characters, they are just displayed with their hex value.

# rexgrep -e "здравей" -N -D
State 0:  REX_STATETYPE_START 
        0x437                           -> 1

State 1: 
        0x434                           -> 2

State 2: 
        0x440                           -> 3

State 3: 
        0x430                           -> 4

State 4: 
        0x432                           -> 5

State 5: 
        0x435                           -> 6

State 6: 
        0x439                           -> 7

State 7:  REX_STATETYPE_ACCEPT 
        (none)

Example 3 - Display DFA with the NFA substates.

# rexgrep -e "здравей" -S -D
State 0 ():  REX_STATETYPE_DEAD 
    [0x0 - 0xFFFFFFFF]                  -> 0

State 1 (0):  REX_STATETYPE_START 
    [0x0 - 0x436]                       -> 0
    0x437                               -> 2
    [0x438 - 0xFFFFFFFF]                -> 0

State 2 (1): 
    [0x0 - 0x433]                       -> 0
    0x434                               -> 3
    [0x435 - 0xFFFFFFFF]                -> 0

State 3 (2): 
    [0x0 - 0x43F]                       -> 0
    0x440                               -> 4
    [0x441 - 0xFFFFFFFF]                -> 0

State 4 (3): 
    [0x0 - 0x42F]                       -> 0
    0x430                               -> 5
    [0x431 - 0xFFFFFFFF]                -> 0

State 5 (4): 
    [0x0 - 0x431]                       -> 0
    0x432                               -> 6
    [0x433 - 0xFFFFFFFF]                -> 0

State 6 (5): 
    [0x0 - 0x434]                       -> 0
    0x435                               -> 7
    [0x436 - 0xFFFFFFFF]                -> 0

State 7 (6): 
    [0x0 - 0x438]                       -> 0
    0x439                               -> 8
    [0x43A - 0xFFFFFFFF]                -> 0

State 8 (7*):  REX_STATETYPE_ACCEPT  (7*)
    [0x0 - 0xFFFFFFFF]                  -> 0

Here is a complete list of available command line options.

Usage: 
 rexgrep [OPTIONS] <filename>
 OPTIONS:
	-e patterns              Regular Expression.
	-f patternfile           Read Regular Expressions from a file.
	-b binfile               Use DFA from binfile.
	-c                       Compile DFA and save to binfile. Use -b option to specify the name of the file.
	-o, --only-matching      Show only the part of a line matching PATTERN
	-l                       Line mode.
	-N                       Use NFA.
	-D                       Dump states.
	-S                       Include DFA substates.
	-q                       Quiet mode.
	-t                       Display statistics. Works only when built in DEBUG mode.
	-s string                Search in string.
	-v                       Display version information.
	-h, --help               Display this help.