greg/just
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

Document how shebang recipes are executed (#1412)

Browse Source
This commit is contained in:
Casey Rodarmor 2022-11-15 18:13:03 -08:00 committed by GitHub
parent 755ac61bee
commit 38a5481cbb
No known key found for this signature in database
GPG Key ID: 4AEE18F83AFDEB23
1 changed files with 17 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

18
README.md
View File

@ -1695,7 +1695,9 @@ This has limitations, since recipe `c` is run with an entirely new invocation of
### Writing Recipes in Other Languages ### Writing Recipes in Other Languages
Recipes that start with a `#!` are executed as scripts, so you can write recipes in other languages: Recipes that start with `#!` are called shebang recipes, and are executed by
saving the recipe body to a file and running it. This lets you write recipes in
different languages:
```make ```make
polyglot: python js perl sh ruby polyglot: python js perl sh ruby
@ -1736,6 +1738,20 @@ Yo from a shell script!
Hello from ruby! Hello from ruby!
``` ```
On Unix-like operating systems, including Linux and MacOS, shebang recipes are
executed by saving the recipe body to a file in a temporary directory, marking
the file as executable, and executing it. The OS then parses the shebang line
into a command line and invokes it, including the path to the file. For
example, if a recipe starts with `#!/usr/bin/env bash`, the final command that
the OS runs will be something like `/usr/bin/env bash
/tmp/PATH_TO_SAVED_RECIPE_BODY`. Keep in mind that different operating systems
split shebang lines differently.
Windows does not support shebang lines. On Windows, `just` splits the shebang
line into a command and arguments, saves the recipe body to a file, and invokes
the split command and arguments, adding the path to the saved recipe body as
the final argument.
### Safer Bash Shebang Recipes ### Safer Bash Shebang Recipes
If you're writing a `bash` shebang recipe, consider adding `set -euxo pipefail`: If you're writing a `bash` shebang recipe, consider adding `set -euxo pipefail`: