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Lines

Lines Is Not Exactly Sed

Sed-inspired line processor using modern Python regex and format syntaxes

Random Thoughts

  • Keep common usage as simple as possible; Sled was too complicated
    • Make some sophisticated things possible, though, especially pre- and post-context lines
  • How much should we enable sed-isms? (e.g. -e 's/foo/bar/g as alias for trans/foo/bar/all?)

To Do

  • DONE: Start with only stdin, no files; cat in whatever you want

  • Handle stdout closing (e.g. lines ... | head)

  • Add file args; file names may be useful context when doing multi-file processing

  • Parse args

    • lines COMMAND ... -- FILE ... or lines -e COMMAND -e... FILE ...?
      • Leaning toward the former, but latter is more standard
    • Commands are command + separator ((?P<cmd>[a-z]+)(?P<sep>[^a-z])), fields split by separator, command options
      • Separator is a single character following the command, used through the rest of the command; no escape sequence, use onethat doesn't appear; recommend bullet (•) - not used in regex, easy to type (opt-8)
      • Short and long commands? - YES, quick vs. readability/maintainability uses for both with commands and options
      • Short and long options? - YES
        • Option syntax?
          • Maybe something like(?P<short_letters_block>[\w-]*);?(?P<long_opt>[\w-]+(:(?P<opt_arg>[\w-]+(,...)?)?;?...)
          • Definitely want option-parser utility, operations should get kwargs
            • Should common options like RE flags be parsed here?

  • Top-level options

    • Add argparse
    • Script file option
    • Trace/verbose/debug
    • Default pass/drop?
    • Help
      • Build command help from CMD_MAP and Operation class docstrings

  • Processors

    • Commands map to processors which form a pipeline
    • Init with parsed args and options
    • Called with (line, context)
      • Return (line, context) or (None, context)
      • If line is None, stop processing and read next

  • Operations

    • f filter: pass only matching lines; option to invert
      • Match or search? Easy enough to add .* or to anchor ^ to flip
      • Option to pass unmatched lines? Explicitly drop unmatched lines?
        • drop / pass / pass-other-matches? Any others?
    • t transform: match line pass formatted version; option to pass/drop unmatched lines
    • Others? Mine sed: Sed - An Introduction and Tutorial

  • Meta-commands?

    • Macro definitions that can be used as arguments in other commands?
    • Buffering for pre-context?
    • Print control for post-context or to change default pass/drop?
    • Store/recall to move extracted values between lines?
      • Indentation level?
    • If/else?
    • Global else? (i.e. all the lines that were simply passed by other operations)
    • Operate on file-change?

Doneyard