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Full Discussion: help running strace
Top Forums UNIX for Advanced & Expert Users help running strace Post 302089986 by klam on Thursday 21st of September 2006 08:03:59 PM
Old 09-21-2006
help running strace

OK so I wanted to know how does grep outputs to the pipe and how sort reads from it. So I run a strace over "grep blah myfile | sort" and this is what I got:

open("myfile", O_RDONLY|O_LARGEFILE) = 3
fstat64(3, {st_mode=S_IFREG|0600, st_size=84, ...}) = 0
read(3, "blah blah and blah cause of blah"..., 32768) = 84
fstat64(1, {st_mode=S_IFIFO|0600, st_size=0, ...}) = 0
mmap2(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xb7fe8000
read(3, "", 32768) = 0
close(3) = 0
write(1, "blah blah and blah cause of blah"..., 85) = 85
close(1) = 0
munmap(0xb7fe8000, 4096) = 0
exit_group(0) = ?
Process 14533 detached
blah blah and blah cause of blah
find blah myfile blah grep it.
this is my blah file

I know that grep nor sort are aware of the pipe, they just input/output to the stdin/stdout... the pipe just connect them, that's how pipes works as far as I know... but what I don't see in this code is how grep is outputing to the pipe (stdout) and how is sort reading from the pipe (stdin). Is there anyway to check that relation? All I can tell from the code I bolded is:

MyFile -> Grep --------------------------> stdout

Unless "read(3, "", 32768)" has anything to do with the sort process.
Thanks in advance.
 

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CSS::DOM::Rule(3pm)					User Contributed Perl Documentation				       CSS::DOM::Rule(3pm)

NAME
CSS::DOM::Rule - CSS rule class for CSS::DOM VERSION
Version 0.14 SYNOPSIS
use CSS::DOM::Rule ':all'; # import constants use CSS::DOM; $sheet = new CSS::DOM; $sheet->insertRule('bla blah blah {}'); $rule = $sheet->cssRules->[0]; $rule->type; # STYLE_RULE $rule->cssText; # 'bla blah blah {}' or similar $rule->cssText('p { margin: 0 }'); # replace it $rule->parentStyleSheet; # $sheet DESCRIPTION
This module provides the CSS rule class for CSS::DOM. It implements the CSSRule and CSSUnknownRule DOM interfaces. METHODS
Constructor Only call the constructor on this class to create an 'unknown' rule. You have to call the constructor on a particular subclass to get another type. Normally you do not need to call this directly anyway. (See CSS::DOM's "parse" and "insertRule" methods.) But just in case you do want to call it, here it is: new CSS::DOM::Rule $parent; # unknown rule require CSS::DOM::Rule::Style new CSS::DOM::Rule::Style $parent; # etc. $parent is the parent rule, if the rule is nested, or the parent style sheet otherwise. Object Methods type Returns one of the constants below indicating the type of rule. cssText Returns this rule's CSS code. If you pass an argument, it will be parsed as the new CSS code for this rule (replacing the existing data), and the old value will be returned. This method will die if the replacement CSS code creates a different type of rule. parentStyleSheet This returns the style sheet to which the rule belongs. parentRule This returns the rule's parent rule, if there is one, or an empty list otherwise. There is only a parent rule if this one is nested, e.g., inside a media rule. EXPORTS
The following constants that indicate the type of rule will be exported on request (individually or with the ':all' tag): UNKNOWN_RULE STYLE_RULE CHARSET_RULE IMPORT_RULE MEDIA_RULE FONT_FACE_RULE PAGE_RULE SEE ALSO
CSS::DOM CSS::DOM::Rule::Style CSS::DOM::Rule::Media CSS::DOM::Rule::Page CSS::DOM::Rule::Import perl v5.10.1 2010-12-10 CSS::DOM::Rule(3pm)
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