bh-altsysrq/hasher-cli

Purpose and Entry Point

hasher-cli is a native command-line utility that computes a file’s SHA-256 digest. Its executable entry point and all runtime logic are in hasher-cli.c; users invoke it with one file-path argument.

Paths:

• hasher-cli.c

• README.md

Build and Runtime Boundary

The project is compiled through make, with build rules defined in Makefile. It requires OpenSSL development headers and links against OpenSSL’s crypto facilities. The produced binary runs directly on the host; there is no server, persistent storage, or application framework.

Paths:

• Makefile

• hasher-cli.c

Command-Line Input Stage

The program receives the target filename from process arguments. Argument handling establishes the primary user boundary: an invalid invocation or inaccessible path should terminate before digest output. The supplied path is treated as a local filesystem resource.

Paths:

• hasher-cli.c

File Streaming Stage

The target file is opened and read from the operating system filesystem. Content is expected to be processed incrementally rather than modeled as application-domain data, keeping memory use independent of file size and separating file I/O failures from cryptographic failures.

Paths:

• hasher-cli.c

SHA-256 Digest Stage

Hash computation is delegated to the OpenSSL EVP API, rather than implementing SHA-256 internally. The EVP context lifecycle—creation, SHA-256 initialization, repeated updates from file chunks, and finalization—forms the central control flow.

Paths:

• hasher-cli.c

Output and Error Boundaries

After finalization, the binary digest is rendered as a human-readable hexadecimal SHA-256 value and written to standard output. Usage, file-access, allocation, and OpenSSL operation failures are command-line error boundaries and should be reported through standard error with a non-success exit status.

Paths:

• hasher-cli.c

External Dependencies

OpenSSL is the only material external service/library dependency, specifically its EVP cryptographic interface and development headers. Host filesystem access supplies the hashed bytes; shell invocation and standard streams provide the interface contract.

Paths:

• hasher-cli.c

• Makefile