# I built the tool my agent-guard README said didn't exist yet

> Source: <https://dev.to/haoli/i-built-the-tool-my-agent-guard-readme-said-didnt-exist-yet-5acp>
> Published: 2026-10-21 08:00:47+00:00

`targets 'make 2>&1 | tee build.log'` → prints `build.log`. That's the whole

pitch: give **bash-write-targets** a bash command string, get back the list

of files it may write to — before anything runs.

``` bash
pip install bash-write-targets

$ targets 'grep -r foo . | sort -o sorted.txt; mv sorted.txt final.txt'
sorted.txt
final.txt

$ targets --json 'sed -i "s/a/b/g" config.ini && curl -s -o app.tgz https://example.com/app'
["config.ini", "app.tgz"]
```

My [agent-guard](https://github.com/hahahahahahahahah6/agent-guard) project

ships a Bash PreToolUse hook that audits commands before an AI agent runs

them. Its README has an *Honest limitations* section, and one bullet reads:

**Bash write-target extraction is static and approximate.** ... **This is the documented frontier for a future version, not a finished parser.**

So I built the future version — as a standalone, stdlib-only tool anyone can

use, hook or no hook.

What it catches: `>` `>>` `&>` `2>`, heredocs (bodies are stripped so

`<<EOF` content isn't mistaken for targets), `$(...)` and backticks

(scanned recursively), `tee` (all operands, `-a` aware), `cp`/` mv`/` install`

destinations, `sed -i` (script vs. file disambiguation), `dd of=`,

`truncate`, `touch`, `zip` archives, and `-o`/`--output` flags for `curl`,

`wget`, `gcc`, `sort`, `pandoc`, `psql`, `tar -f`.

What it deliberately skips instead of guessing: `/dev/null`, fd

duplications (`2>&1`), unresolvable `$VAR` s, bare globs.

Pure static parsing over the command string. Nothing is executed, no

subshell is spawned, no file is touched — auditing a destructive command

cannot itself be destructive. And it's conservative by design: a missed

target is a miss, never a crash. Malformed input yields fewer results, not

an exception.

`eval`, paths assembled at runtime, and `python3 -c "open(p).write(x)"`

are known gaps. Network sinks (`curl --data` POSTing somewhere) are out of

scope — this lists *file* write targets. 19/19 smoke tests green.

`pip install bash-write-targets` (