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A portable Common Lisp library for running external programs from within Lisp.
Common Lisp NewLisp
Latest commit 9f6d518 Mar 6, 2016 @sellout Merge pull request #29 from luismbo/sbcl-process-id
sbcl: implement PROCESS-ID
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external-program.asd Moved the utility functions to a new file and out of the API definition. Jan 15, 2011


EXTERNAL-PROGRAM enables running programs outside the Lisp process. It is an attempt to make the RUN-PROGRAM functionality in implementations like SBCL and CCL as portable as possible without sacrificing much in the way of power.

Note: This library is available via Quicklisp.

Here are some of the differences:

  • splits START (async) and RUN (sync) into two separate functions, rather than using a single function with a WAIT parameter that changes the function's specification;
  • offers a REPLACE-ENVIRONMENT-P parameter that indicates whether provided env vars should build on or replace the current environment.

Read the API documention for details. It’s a bit spartan, but should explain a lot.

Not all functionality is available on all platforms. EXTERNAL-PROGRAM provides warnings and errors when these limitations are encountered. But I'll try my best to work around them.

There is currently at least some support for:

  • Allegro (blocking only)
  • Armed Bear (blocking only)
  • CLisp
  • Clozure CL (née OpenMCL)
  • ECL
  • LispWorks
  • SBCL

In addition to some implementations only providing blocking calls, some don’t use $PATH – the ones that don’t won’t find bareword commands, you’ll need to use a pathname.

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