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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LEARN ABOUT DEBIAN
css::dom::rule
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)