snag

modern stream pattern extractor

a single-purpose unix filter that reads stdin, matches a target pattern against each line, and writes matches to stdout.

install

# arch linux (aur)
paru -S snag-bin

# from crates.io
cargo install snag-cli

# from source
git clone https://github.com/programmersd21/snag.git
cd snag && cargo install --path .

usage

snag <target>
<stream> | snag <target>

targets

target	description	example
ip	ipv4 and ipv6 addresses	echo "host 10.0.0.1" | snag ip → 10.0.0.1
url	http:// and https:// urls	echo "see https://example.com" | snag url → https://example.com
num	standalone integers	echo "code: 404 retries: 2" | snag num → 404, 2
hash	hex strings 7–64 chars (sha, md5)	echo "commit a1b2c3d" | snag hash → a1b2c3d
path	absolute unix file paths	echo "at /var/log/syslog" | snag path → /var/log/syslog
email	email addresses	echo "to user@example.com" | snag email → user@example.com
.<key>	top-level field from ndjson stream	echo '{"id": 42}' | snag .id → 42
:<n>, /<n>, ,<n>	1-indexed column delimiter split	echo "root:x:0" | snag :1 → root
<pre>{}<post>	literal template with wildcard capture	echo "id=[123]" | snag 'id=[{}]' → 123
<regex>	raw regex fallback (group 1 or match)	echo "port=8080" | snag 'port=(\d+)' → 8080

examples

# extract unique ips from server logs
tail -n 1000 /var/log/nginx/access.log | snag ip | sort -u

# extract commit hashes from git log
git log --oneline | snag hash

# extract json fields from an ndjson stream
docker events --format '{{json .}}' | snag .action

# column extraction without awk syntax
cat /etc/passwd | snag :1

# wildcard capture with literal auto-escaping
kubectl get pods | snag 'pod/{}-'

behavior

• delimiter splitting: column mode (:n, /n, ,n) performs a literal byte split without csv quote parsing.
• utf-8 handling: invalid byte sequences are replaced per line with the unicode replacement character (u+fffd) without aborting.
• exit codes: returns 0 on clean runs (including 0 matches) and 1 on invalid arguments or uncompilable patterns.

license

mit