/var/tmp/xmas.txt, each unix cmd could only be used once | Hacker News Reader

xmas.txt, each unix cmd could only be used once

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17 pointsbemmu9 comments

This reminds me of "Eastern Polish Christmas Tree Notation": http://www.kuro5hin.org/story/2004/6/1/43942/41236

Eastern Polish Christmas Tree Notation is the default formatting style for Objective-C method invocation, with widespread editor support!

"echo" isn't a command?

In some shells (such as tcsh) it is a built-in command like "if" or "cd".

yeah, i wondered about that (in bash it's /bin/echo, fwiw - i looked).

Huh? /bin/echo is an executable, all shells should invoke that binary when given a path to it. In bash, echo is a builtin (it appears in the SHELL BUILTIN COMMANDS section of the man page between disown and enable).

  bash$ echo --help # the builtin
  --help
  bash$ /bin/echo --help # the executable
  Usage: /bin/echo [SHORT-OPTION]... [STRING]...
    or:  /bin/echo LONG-OPTION
  Echo the STRING(s) to standard output.
  (and a bunch of other GNU help text)

ah, ok. that makes sense. i just did "which echo" without thinking enough....

Try "type echo".

If "which" is not a builtin (which it isn't in bash, but is in zsh) then it can't tell you about builtins!

While it's vague, I think the spirit of the "challenge" is that once a command has been used, you should not use it again.

Although one can make a cat() function in bourne-esque shells such as bash quite easily:

cat() { while IFS="" read l ; do echo "$l" ; done < $1 ; } ; cat /var/tmp/xmas.txt

Bunch of other stuff you can do with only bash built-ins if you manage to completely hose your box but still have a root shell: http://www.h-i-r.net/2009/08/cratered-your-linux-box-here-ar...

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