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Shell redirection doubt

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# 1  
Old 10-09-2010
Shell redirection doubt
Hi,

Could anyone explain me why I am getting the 'broken pipe' error for the below?

Code:
exec 3>&1
echo cat | cat <&3

-su: echo: write error: Broken pipe
# 2  
Old 10-09-2010
What are you trying to echo? At the least, you should put quotes around cat | cat <&3. But that will just display it.
# 3  
Old 10-09-2010
I am confused with what it is you are trying to do, but I can answer the question about the pipe.

The echo cat portion of the command is trying to write the command line tokens (cat in this case) to the standard output device. You've piped the standard output device to another command, and if were left at that there'd be no error.

The error is coming as a result of your redirecting standard input to the second command (also cat) which is causing the pipe created for the first command to be invalid. When the echo command attempts to write to the invalid pipe, it receives a 'broken pipe' signal and that is what is being announced.
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