Stat a file's size.

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Paul M. Rodriguez <>




This library exports a single function, file-size-in-octets. It returns the size of a file in bytes, using system calls when possible.

The canonical way to determine the size of a file in bytes, using Common Lisp, is to open the file with an element type of (unsigned-byte 8) and then calculate the length of the stream. This is less than ideal. In most cases it would be better to get the size of the file from its metadata, using a system call.

This is a problem I have run into several times in several different projects. I want it solved, once and for all.

At the moment, getting the file size from metadata is supported for the following Lisps:

  • SBCL
  • Clozure CL
  • Allegro CL
  • ABCL
  • GCL
  • LispWorks (on Unix only)
  • ECL (on Unix only)

For other Lisps and platforms, we fall back to opening the file and calling file-length on the stream.

This library is as much a call to arms as it is a resource. If you know how to stat a file on your Common Lisp implementation, on your platform, please make a pull request -- or just open an issue to point me to the right documentation, and I'll do all the work.

Dependencies (2)

  • fiveam
  • uiop

Dependents (3)

  • GitHub
  • Quicklisp