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From: RedGrittyBrick on 2 Jun 2010 11:55
On 02/06/2010 16:08, chad wrote:
> On Jun 1, 10:22 am, Martijn Lievaart<m...(a)rtij.nl.invlalid> wrote:
>> On Tue, 01 Jun 2010 02:26:59 -0700, Peng Yu wrote:
>>> On Jun 1, 3:24 am, Martijn Lievaart<m...(a)rtij.nl.invlalid> wrote:
>>>> On Mon, 31 May 2010 20:47:22 -0700, Peng Yu wrote:
>>>>> diff can take two input streams in the following example (if my
>>>>> interpretation is correct).
>>
>>>>> diff<(gunzip<a.gz)<(gunzip b.gz)
>>
>>>>> I'm wondering how to take two streams in a perl program.
>>
>>>> This has nothing to do with diff or with perl, it's a function of your
>>>> shell. So it works the same for diff as for perl.
>>
>>> I think that I understand what you mean.<(cmd) is just like a filename,
>>> right?
>>
>> It actually gets passed to your program as a filename, although it really
>> is a pipe to the command between the brackets.
>>
>> [martijn(a)cow t]$ perl -e 'print "@ARGV\n"'<(cat t.pl)<(cat t.pl~)
>> /proc/self/fd/63 /proc/self/fd/62
>> [martijn(a)cow t]$
>>
>
> Why do you use the brackets in '<(cmd)'? Ie, why can't you just do
> something like '<cmd' ?

Because the shell would look for a data file named 'cmd' in the current
directory and would not execute it as a command.

$ wc -l <ls
-bash: ls: No such file or directory

$ wc -l <(ls)
105 /dev/fd/63


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