rdiff — CLI reference

The binary is built on cobra, so --help (and -h) is available on every command, and --version prints the build.

rdiff signature

rdiff signature [flags] BASIS SIGNATURE

Compute the signature of BASIS.

Flags:
  -b, --block-size int    signature block size in bytes (default 2048)
  -H, --hash string       strong-sum hash: blake2 or md4 (default "blake2")
  -S, --strong-size int   truncate strong sum to this many bytes (0 = full digest)
  -h, --help              help for signature

The signature lists, per block of BASIS, a 4-byte rolling weak checksum and a (optionally truncated) strong checksum. Smaller --block-size → finer change detection but a larger signature.

rdiff delta

rdiff delta SIGNATURE NEWFILE DELTA

Compute the delta from SIGNATURE's basis to NEWFILE.

A rolling weak checksum slides over NEWFILE; weak-sum hits are confirmed by the strong sum and emitted as COPY commands referencing the basis, while unmatched runs become LITERALs.

rdiff patch

rdiff patch BASIS DELTA NEWFILE

Apply DELTA to BASIS, producing NEWFILE.

BASIS must be a regular file — COPY commands read it at random offsets, so it cannot be a stream.

Conventions

- argument	stdin/stdout for the streamable I/O of each command
Exit code 0	success
Exit code 1	any error (IO, malformed signature/delta, bad magic)

On-disk formats

File	Magic (big-endian)
delta	0x72730236
signature (MD4)	0x72730136
signature (BLAKE2b)	0x72730137

These are the librsync magics, so files are interchangeable with the C rdiff. See Wire compatibility.