`hash` 0.1.0

SHA-256 or SHA-512 of files of any size, as NDJSON records, with --verify; the hash write --if-sha256 wants, from a tool that cannot write.

hash [--root DIR] [--algo sha256|sha512] [--verify HEX] [--format ndjson|text] PATH...

output: NDJSON stream ending in an end record
schema: hash.v1
reversibility: reversible-cheap
guarantees: deterministic, idempotent, bounded_memory
concurrency: read-only: it never writes, so any number may run at once
confinement: beneath: with --root, paths are checked lexically against it and then opened beneath it one component at a time, following no symbolic link (path.symlink), so nothing outside the root is reachable through one; without it, a reader opens the path as given, links and all, and a writer still follows no link in the file's own name
reads the environment: no
reads the clock: no
compiler: de4e52fd8180
for an agent: SKILL.md (hash skill)

Authority

Derived by cancho authority from the source, embedded in the binary, and checked against tools.toml's ceiling in CI. Every label is bounded.

args
dir_read
err_write
file_read
fs_read("")
heap
io_write

What the row cannot say:

path extent: a path from the command line is checked at run time, so the row says fs_read("")
what a symlink reaches
what standard output carries
resource use beyond the tool's own caps (memory, wall time)
per-invocation behaviour such as --dry-run, which the row cannot see

Operands

Operand	Role	How many	Meaning
`PATH...`	`path-read`	1 or more	the files to hash, in order (one with --verify)

Flags

Flag	Kind	Role	Default	Meaning
`--root`	`path`	`root`		resolve every PATH relative to this directory and refuse paths outside it
`--algo` `-a`	`choice:sha256/sha512`	`none`	`sha256`	the digest
`--verify`	`text`	`none`		the expected digest in lowercase hex, takes one PATH, and a difference is precondition.hash-failed
`--format`	`choice:ndjson/text`	`none`	`ndjson`	ndjson for a program, text (sha256sum's layout) for a person

Exit codes

Code	Name	Meaning
0	`SUCCESS`	what was asked was done; zero matches is success
1	`GENERAL_ERROR`	the operating system failed mid-operation, or the tool caught a bug in itself
2	`INVALID_ARGS`	the invocation is malformed or names something of the wrong kind; nothing was read
3	`NOT_FOUND`	a named input does not exist
4	`PERMISSION_DENIED`	the operating system refused, or the tool's own confinement did
8	`PRECONDITION_FAILED`	the answer is no, or a limit was reached

Rules (18)

Match on rule, not on the message. A retry repair is an argv that can be run as it stands, and never widens what the tool may touch.

Rule	Exit	Repair	When
`args.unknown-flag`	2	sometimes	a flag that is not in the tool's table
`args.missing-value`	2	never	a flag that takes a value was given none
`args.bad-value`	2	never	a flag's value is not of the flag's kind
`args.duplicate-flag`	2	never	the same flag was given twice
`args.missing-operand`	2	never	an operand the tool needs was not given
`args.too-many-operands`	2	never	more operands than the tool takes
`path.empty`	2	never	an empty path
`path.dotdot`	2	sometimes	a path with a `..` component
`path.absolute`	2	always	an absolute path where one relative to --root is wanted
`path.outside-root`	4	never	an absolute path that is not under --root
`path.too-long`	2	never	a path longer than 4096 bytes
`path.symlink`	4	never	a path that runs through a symbolic link, which the tool does not follow
`io.not-found`	3	never	a named input does not exist
`io.not-a-directory`	3	never	a path runs through something that is not a directory
`io.is-a-directory`	2	never	a directory where a file is wanted
`io.permission-denied`	4	never	the operating system refused access
`io.read-failed`	1	never	the operating system failed a read
`precondition.hash-failed`	8	never	--verify was given and the digest differs

Evidence

each gate is a test in cancho-tools/tests/conformance, run by CI on the commit this binary was built from:

M1 schema conformance
M2 determinism
M3 rule coverage and hint soundness
M4 fault injection
M5 differential against GNU
M6 authority
M7 mutation behaviour
M8 confinement
M9 memory flatness

Agent in the loop: not run: no claim that this tool is more agent-friendly than the incumbents is made (cancho docs/agent-toolbox.md section 7.2).