https://github.com/twosigma/relexec

A program to enable relative shebangs in scripts
https://github.com/twosigma/relexec

scripts unix

Last synced: 30 days ago
JSON representation

A program to enable relative shebangs in scripts

• Host: GitHub
• URL: https://github.com/twosigma/relexec
• Owner: twosigma
• License: apache-2.0
• Created: 2021-05-12T14:49:28.000Z (over 3 years ago)
• Default Branch: main
• Last Pushed: 2021-05-14T09:55:32.000Z (over 3 years ago)
• Last Synced: 2024-11-07T03:14:17.952Z (3 months ago)
• Topics: scripts, unix
• Language: Python
• Homepage:
• Size: 21.5 KB
• Stars: 2
• Watchers: 6
• Forks: 0
• Open Issues: 5
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

Awesome Lists containing this project

README

        
# Relexec

![GitHub Workflow Status](https://img.shields.io/github/workflow/status/twosigma/relexec/Run%20tests)

![GitHub](https://img.shields.io/github/license/twosigma/relexec)

`relexec` is a helper program to enable "relative shebangs".

Relative shebangs are not natively supported on POSIX systems. Paths specified

as relative in shebangs are resolved relative to the current working directory,

behaviour which is almost useless.

To work around this, a shebang can be specified with the `relexec` program,

installed in a well-known path. `relexec` constructs a path relative to the

script and execs it.

This allows scripts to be defined that run with interpreters installed with the

script. These can then run from anywhere in the filesystem, or be moved to

another location without breaking (as long as the relative path between the

script and interpreter does not change).

Unlike other solutions to this problem, it is easy to programmatically rewrite

shebangs to use relexec (or rewrite them back).

## Usage

The intended usage is in the shebang line of a script:

```

#!/usr/lib/relexec python3.9

```

which would define that the script should be executed with an executable

named `python3.9` in the same directory as the script.

Specifically, if the script is in `/path/to/file`, then executing

`/path/to/file arg1 arg2` would run relexec with this command line:

```

/usr/lib/relexec python3.9 /path/to/file arg1 arg2

```

which relexec transforms to

```

/path/to/python3.9 /path/to/file arg1 arg2

```

and `exec()`s the result.

## Installation

We provide C, Rust, and for reference, Python versions of `relexec`.

We specify that the `relexec` binary, if installed, must be installed to

`/usr/lib/relexec` so that this path can be hard coded in shebangs.

`/usr/lib` is the appropriate place for internal binaries according to the

[Filesystem Hierarchy Standard 3.0](https://refspecs.linuxfoundation.org/FHS_3.0/fhs/ch04s06.html),

as `/usr/libexec` does not exist on all systems.