08df164692
- #25: $VAR expansion in commands - #26: Shell abbreviations and user-extensible builtins - #27: $(cmd) subcommand syntax - #22: Updated with implementation details (in progress) - #7: Standardize status label
52 lines
1.6 KiB
Markdown
52 lines
1.6 KiB
Markdown
# 25 — Environment variable expansion in commands
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**Status:** open
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## Problem
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`$VAR` syntax works in Lua expressions but not inside commands:
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```lua
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print($PATH) -- works: $PATH is lexed as TK_ENVVAR, expanded via getenv()
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!echo $PATH -- broken: $PATH is kept as literal text, passed unexpanded
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```
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The same applies to backtick commands:
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```lua
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local r = `echo $HOME` -- $HOME is literal, not expanded
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```
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## Why it happens
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The lexer has two separate paths for `$`:
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1. **In Lua code** (`llex.c:667`): `$NAME` → `TK_ENVVAR` token → compiled to `getenv("NAME")` call
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2. **In command mode** (`llex.c:518`): `$` without `{` is saved as a literal character in the command string buffer
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Only `${expr}` interpolation works in commands — it enters a Lua expression context and returns the result inline. Bare `$NAME` is passed through verbatim.
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Since commands are executed via `fork`/`exec` (not through `/bin/sh`), there is no shell to expand `$PATH` at runtime either.
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## Expected behavior
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`$VAR` should expand in commands the same way it does in Lua expressions:
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```lua
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!echo $HOME -- should print /Users/nik
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!echo $PATH -- should print the PATH value
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local r = `echo $HOME` -- r.stdout should contain /Users/nik
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```
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## Workaround
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Use `${expr}` interpolation:
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```lua
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!echo ${$HOME}
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```
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## Possible fix
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In `read_command_body()` (`llex.c:518`), when `$` is followed by an identifier, emit the current command fragment and produce a `TK_ENVVAR`-equivalent expansion inline — similar to how `${expr}` already splits the command string to insert interpolated values.
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