[chaliy]

Requested by Михайло · project thread

What changed

Redirections to /dev/stdin, /dev/stdout, /dev/stderr and /dev/fd/N now behave like on Linux: they alias the descriptor's current target (> /dev/stderr is >&2, > /dev/fd/3 is >&3, < /dev/stdin keeps stdin, exec 3>/dev/stderr dups fd 2). They are resolved at the interpreter level like /dev/null and never reach the VFS. Covers the fast redirect path, the fd-table path (mixed 2>&1 + file), &>, >>, variable targets and .. spellings.

First PR of the "closer to real bash" roadmap (Step 1, fidelity bugs).

Why

echo err > /dev/stderr silently wrote a 3-byte regular file /dev/stderr in the VFS and printed nothing. Agents use this pattern constantly for error messages, so errors vanished.

Before / After

$ bashkit -c 'echo err > /dev/stderr; ls -l /dev'
# before: (no output on stderr)
-rw-r--r--   3 ... stderr        <- regular file created
# after:
err                               <- on stderr, no file created

Real bash 5.2 cross-checked for the tricky shapes: 2>&1 >/dev/stderr sends both streams to stdout; exec 3>/dev/stderr; echo x >&3 goes to stderr.

Risk

• Low
• Only redirect targets whose normalized path is exactly /dev/std{in,out,err} or /dev/fd/<digits> change behaviour. Process-substitution paths (/dev/fd/proc_sub_*) are untouched. Builtin file operands (tee /dev/stderr, cat /dev/stdin) are a follow-up, noted in knowledge/foundations/vfs.md.

Checklist

• Tests added or updated (12 integration tests, 8 spec cases)
• Backward compatibility considered

https://claude.ai/code/session_019aFikmptPc91Fj4N2iDXQA

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