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Re: Xcode debug follow fork
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Re: Xcode debug follow fork


  • Subject: Re: Xcode debug follow fork
  • From: Greg Guerin <email@hidden>
  • Date: Fri, 14 Nov 2008 15:09:08 -0700

Dee Ayy wrote:

However, sometimes I invoke as follows:
cat my_pipe | ./my_app | tee my_log

Can you show me a stupid cat trick to do that with
./my_app <my_pipe

It's the same basic pattern I tried to illustrate.

Any shell pipeline that looks like this:
  cat a_file | ./any_app

can be replaced by this:
   ./any_app <a_file

There are some situations where this replacement can result in a subtle change, but in general this replacement will work.

The replacement won't work if you have 2 or more files, like this:

  cat a_file b_file | ./any_app

but you didn't say that, so it doesn't apply.


So using the above pattern on this: cat my_pipe | ./my_app | tee my_log

you get this:
  ./my_app <my_pipe | tee my_log

Or if you don't need the output from tee's stdout:
  ./my_app <my_pipe >my_log

This is all elementary I/O redirection and pipeline semantics. If you don't undestand that, you should probably read the relevant sections of the 'bash' man page, or an introductory text on Unix/ Posix. In particular, focus on standard input and standard output streams, and the shell operators, < and >, used for redirecting them to files.

  -- GG

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