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9194 :: passing tab separator as option value

• tcheran (orginal) [2022-06-02T13:24:12+02:00] view original

  Is there a way to pass \t as "tab separator" as on option value (e.g. to set it as separator for a csv output), or the only way is to check against raw string, like this:

  import std/parseopt, std/strutils
  var
    sep: string
    p = initOptParser()
  while true:
    p.next()
    case p.kind
    of cmdEnd, cmdArgument: break
    of cmdShortOption, cmdLongOption:
      continue
  let strseq = ["just","a","test"]
  # don't want just\ta\ttest output
  if p.val == r"\t":
    sep = "\t"
  else:
    sep = p.val
  echo(strseq.join(sep))
   
  Run

  to achieve proper output?

   $ cmdtest --sep:\t
  just    a       test
  Run

  Thank you

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• cblake (orginal) [2022-06-02T14:06:35+02:00] view original

  Only tested on Unix, but

  proc foo(outsep=' ') = echo ord(outsep)
  import cligen; dispatch foo
  # literal 1-byte hard TAB arg => emits "9\n"
  # literal 2-byte backslash-t also emits "9\n"
  Run

  You may also like other things about cligen.

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• xigoi (orginal) [2022-06-02T14:19:56+02:00] view original

  I couldn't get it to work with std/parseopt, but c-blake's cligen seems to be the solution, and I'd recommend using it anyway:

  import cligen
  
  proc cmdtest(sep: string) =
    const strseq = ["just","a","test"]
    echo strseq.join(sep)
  
  dispatch cmdtest
  Run

  However, you still need to pass a literal tab to the program. In bash/zsh, it can be done like this:

  
  cmdtest --sep:$'\t'
  Run

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• cblake (orginal) [2022-06-02T15:13:24+02:00] view original

  For a string arg, yes you do need that shell syntax to get a literal TAB.

  Besides @xigoi's fine suggestions, you can also just set an environ variable called t='<Ctrl-V>TAB'. I do that for newlines sometimes (called n) where you don't even need the <Ctrl-V> keystroke (^V with typical default stty settings, anyway) - rather just quote-ENTER-quote. Once you have such a variable it's just "$t" or "$n". There is also "printf capture" as in tab="$(printf \\t)" (or tr capture or ..).

  However, as I already showed (in my comment lines), cligen will unescape a single char type for you, though. . And if you hate that then all this is CLauthor-overridable replacing cligen/argcvt.nim definitions between import cligen and dispatch. Documentation could be better. Feel free to hack away at the cligen Wiki.

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• tcheran (orginal) [2022-06-02T16:47:52+02:00] view original

  Thank you @xigoi, @cblake, unfortunately on Windows (my environment) the smart trick to pass the literal Tab to program

   cmdtest --sep:$'\t' 
  Run

  on CMD shell produces

  $'\t'a$'\t'test 
  Run

  and I didn't yet found alternatives. However on Windows PowerShell

  .\cmdtest -s:`t
  just    a       test
  Run

  does work. However this OS environment + shell dependency does not make it the right way to go. While \t is pretty "standard" convention for Tab, `t is not. Thank you for your suggestion of cligen, it seems pretty powerful (the --help API auto-documentation alone is well worth to consider it).

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• xigoi (orginal) [2022-06-02T22:20:14+02:00] view original

  Yeah :/ $'t' is bash-specific syntax, so it doesn't even work in other Unix shells. An alternative is using an actual tab, as @cblake suggested, but it may be hard to enter in some environments. The variable trick is clever.

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