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Re: Use of pipe in $(< filename | program) returns null


From: pk
Subject: Re: Use of pipe in $(< filename | program) returns null
Date: Sun, 29 Nov 2009 00:22:44 +0000

Chet Ramey wrote:

> root@saturn.syslang.net wrote:
> 
>> Description:
>> use of $(< filename | program) does not work. It either should or it
>> should be properly documented. The problem also happens on bash4.
>> 
>> Repeat-By:
>> 
>> qq=$(< /etc/passwd | grep sys)
>> echo $qq
>> # result is null
>> 
>> Fix:
>> Either fix the docs to tell people that a pipe is not allowed or fix the
>> code to allow it.
> 
> That construct is very limited.  As the bash man page says:
> 
> The command substitution $(cat file) can be replaced by the equivalent
> but faster $(< file).
> 
> That seems pretty clear.

Yeah, and then based on that he probably thought that

$(cat file | grep sys)

could be replaced by

$(< file | grep sys)

which is not the case.


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