Can it search more than one file?

Yes. Pass a single file, or point folder-with-files at a directory and it searches across all files in one run.

When should I use a regex filter instead?

Use a pattern-based filter when one fixed string cannot describe the keep set, for example several status codes or a structured token. fgrep-by-string is for exact terms.

Does it need CLI flags?

No. The node wires file or folder-with-files plus fgrep-string as inputs. There are no snapshot CLI flags for this utility.

What marker should I search for?

A domain, status token, vulnerability tag, or any other literal substring that already appears in the lines you want to keep.

Updated Jul 15, 2026

Utilities

Keep lines that contain a fixed marker

Filter file or folder lines by a fixed string.

Filter noisy recon output to what matters Search a whole folder of results at once Gate downstream stages on a marker

overview

What fgrep-by-string does

fgrep-by-string sits between noisy recon stages and downstream probes. Feed a file or folder-with-files plus fgrep-string; it writes matching lines as a file and a folder.

Use it when a host, URL, or scan dump needs a literal marker cut: a domain, status token, or tag. Fixed-string match means dots and slashes need no regex escaping.

Prefer grep-by-line for patterns. Prefer anew for uniqueness, not content. Empty output means the marker never appeared in the input stream.

use cases

Where fgrep-by-string fits

Filter noisy recon output to what matters

Pass a fixed marker such as a domain or a status token so a large URL or host file collapses to the lines that carry it, before they reach the next stage.

Search a whole folder of results at once

Point the folder input at a directory of files from a fan-out stage and pull every matching line across all of them in a single node, without merging them first.

Gate downstream stages on a marker

Keep only records that contain a specific tag, then feed the trimmed set into probing or scanning so those stages spend work only on lines that already qualify.

Match literal strings without regex escaping

Search for terms that contain dots, slashes, or brackets directly, since fixed-string matching treats the input as plain text rather than a pattern.

reference

fgrep-by-string inputs and flags

3 inputs

Name	Type	Flag	Description
file	FILE	·	File whose lines are searched for the fixed string.
fgrep-string	STRING	·	Literal string to match against each line.
folder-with-files	FOLDER	·	Folder of files to search across in one run.

Showing key inputs. fgrep-by-string exposes 3 inputs in total.

example

Run fgrep-by-string

fgrep-by-string · command

# fgrep-by-string: keep host lines that mention example.com# inputs: file=hosts.txt  fgrep-string=example.comfgrep -h -- example.com hosts.txt

sample output

www.example.comapi.example.commail.example.comdev.example.comstaging.example.comcdn.example.comvpn.example.comdocs.example.com

guidance

Choosing fgrep-by-string

Reach for fgrep-by-string when you need a literal filter between pipeline stages: trim a large result set to lines that contain a known marker, or gate later work on that marker. Switch to a regex filter when one fixed term cannot describe the match.

grep-by-line

Matches lines against a pattern rather than a fixed string. Use it when you need regular expressions instead of an exact term.

anew

Appends only new, unique lines to a file. Built for dedup and change detection, not content filtering.

diff-trickest-files

Diffs two files to surface the change set. Better when you want what changed, not what matches a marker.

faq

fgrep-by-string questions

fgrep matches a fixed literal string instead of a regular expression, so special characters in the search term are plain text and never pattern syntax.

Run fgrep-by-string yourself

A file of scan results feeds fgrep-by-string, which keeps only the lines that contain the search string and writes the matches as a queryable output.

Open fgrep-by-string in the library Build a workflow with it

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