db6f39a2a4
Defines syntax decisions and implementation plan across 7 issues:
- backtick command execution returning {code, stdout, stderr}
- ${expr} interpolation in backticks
- $SIGIL env var read/write
- argv parsing, piping, and redirection (future)
1007 B
1007 B
07 — Implement I/O redirection for commands
Status: open (post-core) Blocked by: #03
Syntax
`ls -l` > "output.txt" -- redirect stdout to file
`ls -l` >> "output.txt" -- append stdout to file
`cmd` 2> "err.txt" -- redirect stderr to file
`cmd` 2>&1 -- merge stderr into stdout
`cmd` < "input.txt" -- redirect stdin from file
Implementation
- Before
execvp()in the child process, usedup2()to redirect file descriptors - Parse redirection operators as part of the command syntax
- Open target files with appropriate flags:
>—O_WRONLY | O_CREAT | O_TRUNC>>—O_WRONLY | O_CREAT | O_APPEND<—O_RDONLY
2>&1—dup2(stdout_fd, STDERR_FILENO)
Challenge
> and >> conflict with Lua's greater-than and right-shift operators. Like piping, these operators must only be valid in command context. The parser can disambiguate because the left-hand side is a command expression.