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Show HN: A simple Unix cat implementation in various languages

github.com

2 pointsrspivak6 comments

Here is another implementation using Node.js (although it does not explicitly check for EOF):

  require("fs").createReadStream(process.argv[2]).pipe(process.stdout)

Here is a implementation in PostScript (it does explicitly check for EOF, and specifically deals with one byte at a time):

  /o (%stdout) (w) file def
  ARGUMENTS 0 get (r) file
  {
    dup read {
      o exch write
    } {
      quit
    } ifelse
  } bind loop

(I have no GitHub account. But if the owner of that repository want to add, they can add what I have; I post this message (and all of my other messages on Hacker News) to public domain.)

Thank you for the implementations! Do you have any suggestions how to test the postscript code on mac/linux? I tried on macos using ghostscript, but I get the following error:

$ gs cat.ps helloworld.txt

Error: /undefined in ARGUMENTS ...

Thanks!

To give command-line arguments to a PostScript program in Ghostscript, you must prefix the name of the PostScript file with two minus signs, such as:

  gs -dNODISPLAY -q -- cat.ps helloworld.txt

(The -dNODISPLAY and -q are not needed to get this PostScript program to work, but -dNODISPLAY disables graphical output, and -q avoids Ghostscript's messages getting mixed in with the PostScript program's output. You might also need -dNOSAFER; if you get a invalidaccess error, try that. As far as I know, ARGUMENTS and -- are a feature specific to Ghostscript.)

Feel free to add your own implementation. :)

FWIW, iter() handles the logic of testing for an explicit EOF marker, so another way to write it is:

    import sys

    with open(sys.argv[1]) as fin:
        for c in iter((lambda: fin.read(1)), ""):
            sys.stdout.write(c)

That's a good point. Thanks!

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