Fix file argument detection when stdin is /dev/null#414
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Fixes antonmedv#398 where fx incorrectly treats file paths as code arguments when run in launch agents or other non-TTY contexts with stdin redirected to /dev/null. Root cause: The original code only checked isatty(stdin) to decide between file mode and pipe mode. In launch agents, stdin is not a TTY but also not a pipe (often /dev/null), causing fx to incorrectly assume piped input and treat the file path as JS code. Solution: Check if stdin is an actual input stream (pipe or regular file) vs a character device (/dev/null, /dev/tty). Use os.ModeCharDevice to distinguish: - Character devices (TTY, /dev/null) → file mode - Pipes and regular files → pipe mode This preserves all existing behavior while fixing the launch agent case.
antonmedv
approved these changes
May 11, 2026
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When
fxruns in non-TTY contexts (like macOS LaunchAgents) where stdin is redirected from/dev/null, it incorrectly assumes piped input. It then evaluates the first argument (a file path) as JavaScript, resulting in aSyntaxError(parsing/tmp/package.jsonas a RegExp literal/tmp/with flagspackage.json).Example:
Error:
Previously, we relied solely on
isatty(stdin). This adds a device-type check usingos.ModeCharDevice: character devices (TTY,/dev/null) route to file mode, while non-character devices (pipes, regular files) route to stdin-input mode.Fixes #398