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Show HN: A simple Unix cat implementation in various languages (github.com)
2 points by rspivak 2306 days ago
2 comments
zzo38computer 2306 days ago
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.)
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rspivak 2305 days ago
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!

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zzo38computer 2305 days ago
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.)
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rspivak 2306 days ago
Feel free to add your own implementation. :)
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eesmith 2306 days ago
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)
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rspivak 2305 days ago
That's a good point. Thanks!
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