Echo

Echo is a lightweight logging library for OCaml with C lib bindings, allowing both OCaml and C code to emit structured log messages through a unified logging interface.

Features

• C bindings for easy logging integration with your C lib (see C API section below)
• Supports output to stdout, stderr, and .log files
• Standard log levels: TRACE, INFO, WARN, ERROR, FATAL
• Manual flushing of logs

Installation

Echo can be installed with opam:

opam install echo

opam package page: https://opam.ocaml.org/packages/echo

API Overview

OCaml

val set_out : out_type -> unit
val trace : ('a, unit, string, unit) format4 -> 'a
val info : ('a, unit, string, unit) format4 -> 'a
val warn : ('a, unit, string, unit) format4 -> 'a
val error : ('a, unit, string, unit) format4 -> 'a
val fatal : ('a, unit, string, unit) format4 -> 'a
val flush : unit -> unit

C

Don't forget to #include <echo.h>

void echo_trace(const char *fmt, ...);
void echo_info(const char *fmt, ...);
void echo_warn(const char *fmt, ...);
void echo_error(const char *fmt, ...);
void echo_fatal(const char *fmt, ...);

Example Usage

In OCaml

let main () =
  (* Optional: Redirect logs to a file *)
  Echo.set_out (File "debug.log");

  (* Log from OCaml *)
  Echo.trace "Starting analysis of '%s'" "report.csv";
  Echo.info "Processed %d items" 42;
  Echo.warn "Unusual delay: %.2f ms" 123.45;
  Echo.error "Failed to read file '%s'" "data.bin";
  Echo.fatal "Unrecoverable crash in module '%s'" "engine";

  Echo.flush ()

let () = main ()

In C

#include "echo.h"

void dummie_c_fn()
{
    echo_trace("%s", "message");
    echo_info("%s", "message");
    echo_warn("%s", "message");
    echo_error("%s", "message");
    echo_fatal("%s", "message");
}

License

MIT License — free to use, modify, and distribute.

Contributions

Contributions are welcome! Feel free to open issues or submit PRs if you find bugs or have ideas for improvement.