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executables 

        # Gem::Specification.executables

(from ruby core)
### Implementation from Specification
---
    executables()

---

Executables included in the gem.

For example, the rake gem has rake as an executable. You don’t specify
the full path (as in bin/rake); all application-style files are expected
to be found in bindir.  These files must be executable Ruby files. 
Files that use bash or other interpreters will not work.

Executables included may only be ruby scripts, not scripts for other
languages or compiled binaries.

Usage:

    spec.executables << 'rake'

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