grep-like CLI using Parsec parsers instead of regex.

screp is a grep-like command-line tool that uses Parsec parser combinators instead of regular expressions for pattern matching. Write patterns using a familiar Haskell-like DSL with combinators like 'some digit', 'string TODO', or 'manyTill anyChar (string END)'.

screp

A grep-like CLI that uses Parsec parser combinators instead of regex.

Installation

cabal build screp
cabal install screp

Make sure ~/.local/bin is in your PATH:

export PATH="$HOME/.local/bin:$PATH"

Or install from Hackage:

cabal install screp

Usage

screp PATTERN FILE...
screp [OPTIONS] PATTERN FILE...

DSL Primitives

DSL Combinators

Examples

# Find digits
screp 'some digit' file.txt

# Find email patterns (inline)
screp 'some alphaNum <+> char '\''@'\'' <+> some alphaNum <+> char '\''.'\'' <+> some letter' contacts.txt

# Find TODO comments
screp 'string "TODO"' -r ./src/

# Search recursively with extension filter
screp -r -e .hs 'string "import"' ./src/

# Count matches
screp -c 'digit' data.txt

# JSON output
screp --json 'some digit' file.txt

# Non-greedy matching: find everything between X and Y
screp 'string "START" <+> manyTill anyChar (string "END")' file.txt

Using Custom Parsers (--import)

For complex patterns, define parsers in a Haskell file and reference them with ref:

Parsers.hs:

module Parsers (parsers) where

import Text.Parsec
import Text.Parsec.String
import Data.Map (Map)
import qualified Data.Map as Map

parsers :: Map String (Parser String)
parsers = Map.fromList
  [ ("email", email)
  , ("phone", phone)
  ]

email :: Parser String
email = do
  user <- many1 alphaNum
  char '@'
  domain <- many1 alphaNum
  char '.'
  tld <- many1 letter
  pure $ user ++ "@" ++ domain ++ "." ++ tld

phone :: Parser String
phone = do
  a <- count 3 digit
  char '-'
  b <- count 3 digit
  char '-'
  c <- count 4 digit
  pure $ a ++ "-" ++ b ++ "-" ++ c

Usage:

# Find emails using custom parser
screp --import Parsers.hs 'ref "email"' contacts.txt

# Find phone numbers
screp --import Parsers.hs 'ref "phone"' contacts.txt

Requirements for custom parsers:

• Module must export parsers :: Map String (Parser String)
• Requires parsec and containers packages installed

Options

-r, --recursive      Search directories recursively
-e, --extension EXT  Only search files with extension (e.g., .hs, .txt)
-i, --import FILE    Haskell file with named parsers (for 'ref "name"')
-v, --verbose        Verbose output with full match text
-c, --count          Only print count of matches
-q, --quiet          Quiet mode (exit code only)
-m, --max-results N  Maximum number of results to show
--json               Output results as JSON

Output Format

Default output is grep-like:

file.txt:1:28:123
file.txt:2:5:[email protected]

Format: filepath:line:column:matched_text

Library API

The Scrappy.Grep.* modules expose:

• Scrappy.Grep.DSL - AST types (ParserExpr, MatchResult)
• Scrappy.Grep.DSL.Parser - Parse DSL strings to AST
• Scrappy.Grep.DSL.Interpreter - Convert AST to Parsec parsers
• Scrappy.Grep.Search - File/directory search functions
• Scrappy.Grep.Config - External parser execution via runghc
• Scrappy.Grep.Output - Result formatting.