lfescript.txt

lfescript(1)                                                      lfescript(1)



NAME
       lfescript - Lisp Flavoured Erlang (LFE) scripting support

SYNOPSIS
       lfescript  provides support for running short LFE programs without hav‐
       ing to compile them first and an easy way to retrieve the command  line
       arguments.

EXPORTS
       script-name script-arg1 script-arg2 ...

       lfescript lfescript-flags script-name script-arg1 script-arg2 ...

       lfescript runs a script written in LFE.

       lfescript:script_name() -> File

       Types:

              File = filename()

       The script_name/0 function returns the name of the lfescript being exe‐
       cuted.  If the function is invoked outside the context of an lfescript,
       the behavior is undefined.

EXAMPLE
       Here follows an example script.

              $ cat factorial
              #! /usr/bin/env lfescript
              ;; -*- mode: lfe -*-
              ;;! -smp enable -sname factorial -mnesia debug verbose

              (defun main
                ([(list string)]
                 (try
                     (let* ((n (list_to_integer string))
                            (f (fac n)))
                       (lfe_io:format "factorial ~w = ~w\n" (list n f)))
                   (catch
                     ((tuple _ _ _) (usage)))))
                ([_] (usage)))

              (defun fac
                ([0] 1)
                ([n] (* n (fac (- n 1)))))

              (defun usage ()
                (lfe_io:format "usage: factorial integer\n" ()))

       The  header  of  the  LFE script is different from a normal LFE module.
       The first line is an interpreter line which invokes  lfescript  if  the
       script  is run as in the first command line above.  If lfescript is ex‐
       plicitly invoked in the second command line above then this header line
       will  be  ignored.   On the second or third line it is possible to give
       arguments to the emulator with the syntax:

              ;;! -smp enable -sname factorial -mnesia debug verbose

       In the example the second line is an optional directive to Emacs  which
       causes it to enter LFE mode when editing the script file.

       The  rest of the file contains LFE source code.  It must always contain
       the function main/1.  When the script is  run  this  function  will  be
       called with a list of strings representing the arguments with which the
       script was called.  It is possible to define, include and use macros in
       the source code.

       The source code is checked and warnings and errors will be printed.  If
       there are errors the script will not run and it will terminate with ex‐
       it  status  127.  Otherwise the code will be interpreted.  If the func‐
       tion main/1 returns successfully then the exit status  for  the  script
       will be 0 but if an exception is raised then exit status will be 127.

OPTIONS
       The following option is accepted by lfescript

       · -s  - Only perform a syntactic and semantic check of the script file.
         Warnings and errors (if any) are written to the standard output,  but
         the  script will not be run.  The exit status will be 0 if there were
         no errors, and 127 otherwise.

       Unrecognised options are ignored.

ENVIRONMENT VARIABLES
       LFESCRIPT_EMULATOR

       The command used to start the emulator.  Default is `erl'.  This can be
       useful for passing arguments into the emulator, for example

              LFESCRIPT_EMULATOR="erl -pa sune"

       will add the directory sune to the code path.

SEE ALSO
       lfe(1), lfe_guide(7)

AUTHORS
       Robert Virding.



                                   2013-2016                      lfescript(1)