camlmix [Options...] files...


camlmix processes text templates with embedded OCaml code to generate text again. From one or several input files it generates an OCaml text generation program and executes this to obtain the result. Using option -fun one can also convert the text template into an OCaml text generation function.


-o output

write the generated text into file output


Only generate the text generation program, don't execute it. By default, the program is called when lastfile is the last file argument.

-co file

specify the name of the text generation program


generate OCaml code for text generation function from the input (see ADVANCED USAGE below)

-e ocamlc

set the name of the OCaml executable


remove the text generation program after execution

-insert ocaml_code

insert ocaml_code at the beginning of the text generation program


try a conversion to the camlremix syntax


print version and exit

-help | --help

print help and exit (this man page was written from the output of -help)


Text enclosed with ## markers is considered as a block of OCaml code. It can be any kind of toplevel expressions such as definitions or application of printing functions:

This is ocaml version ## print Sys.ocaml\_version ##

If the OCaml code starts with = then it is interpreted as an expression of type string that will printed like the rest of the text:

This is ocaml version ##= Sys.ocaml_version ##

The text block are printed together with the evaluated OCaml pieces using the print function. Include ### to print ##.

White space can be controlled with ##. and .##:


don't print white space occurring on the left


don't print white space up to and including the first newline, following to the right.



Blocks of code that start with the @ character (possibly preceded by spaces) are directives for Camlmix. There are two directives. include inserts a camlmix file, and skip skips the next block. For instance

Hello ## @include "world.mlx"; skip .## ## let x = 123 ##!

Conversion into a text generation function for dynamic rendering

The -fun option, used in combination with -c and often -co produces an OCaml source file which provides a function render with the following signature:

val render : ?print:(string -> unit) -> 'a -> unit

The polymorphic argument is called param in the generated code and can be used to pass runtime arguments into the render function. The print function is used to set the initial value of Camlmix.printer (see below). It's default value is:

       fun s -> print_string s; flush stdout

Runtime hooks

The text generation program, which camlmix generates, contains a module Camlmix at the beginning, which can be used in code blocks. This module has the following signature.

module Camlmix : sig

val source : string ref

val line : int ref

val char : int ref

Location of the first character of the current block in its source file. Line and character numbers count from 1. These references are updated by camlmix at the beginning of each block.

val printer : (string -> unit) ref

function for printing text blocks

val print_with : (string -> unit) -> unit

print_with f causes the next text block to be printed with f instead of the current printer. Its behavior is undefined if it is called several times in the same code block.

val print_if : bool -> unit

print_if cond prints the next text block only if condition cond is true. It uses print_with internally.


RELATED TO camlmix…

The camlmix web page,


This manual page was written by Sylvain Le Gall <[email protected]> and Hendrik Tews <[email protected]>, specifically for the Debian project (and may be used by others).