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Full Discussion: Confusion with PS
Top Forums Shell Programming and Scripting Confusion with PS Post 302706709 by alister on Thursday 27th of September 2012 08:38:43 AM
Old 09-27-2012
All of the problems witnessed above are the result of the shell forking to create new processes to run a pipeline: ps, grep, wc, another shell for the command substition (in the case of the original post). All of these processes initially begin as a new shell with the same name, $0, as the parent shell.

If ps scans the process list before any of these shells have had a chance to exec and become the utility it will become, the result is multiple instances of $0.

The solution is trivial and widely available: pgrep

Quote:
Originally Posted by sathyaonnuix
I found out the problem Smilie Since we give wc -l, this gets a new line. And hence that has got counted in it.

I changed that to
Code:
ps -ef | grep $0 | grep -cv grep

Now it works cool.
Your analysis is incorrect. You're just getting lucky with timing. In your original wc version, you were unlucky with timing. Nothing has been fixed.

The reason pgrep works reliably is because it's only one command and it doesn't run until after the shell that was forked to create it has exec'd.

Unless the system lacks pgrep and pkill, there's no need to resort to the ps ... | grep/awk ... silliness.

Regards,
Alister
This User Gave Thanks to alister For This Post:
 

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Jcode(3pm)						User Contributed Perl Documentation						Jcode(3pm)

NAME
Jcode - Japanese Charset Handler SYNOPSIS
use Jcode; # # traditional Jcode::convert($str, $ocode, $icode, "z"); # or OOP! print Jcode->new($str)->h2z->tr($from, $to)->utf8; DESCRIPTION
<Japanese document is now available as Jcode::Nihongo. > Jcode.pm supports both object and traditional approach. With object approach, you can go like; $iso_2022_jp = Jcode->new($str)->h2z->jis; Which is more elegant than: $iso_2022_jp = $str; &jcode::convert($iso_2022_jp, 'jis', &jcode::getcode($str), "z"); For those unfamiliar with objects, Jcode.pm still supports "getcode()" and "convert()." If the perl version is 5.8.1, Jcode acts as a wrapper to Encode, the standard charset handler module for Perl 5.8 or later. Methods Methods mentioned here all return Jcode object unless otherwise mentioned. Constructors $j = Jcode->new($str [, $icode]) Creates Jcode object $j from $str. Input code is automatically checked unless you explicitly set $icode. For available charset, see get- code below. For perl 5.8.1 or better, $icode can be any encoding name that Encode understands. $j = Jcode->new($european, 'iso-latin1'); When the object is stringified, it returns the EUC-converted string so you can <print $j> instead of <print $j->euc>. Passing Reference Instead of scalar value, You can use reference as Jcode->new($str); This saves time a little bit. In exchange of the value of $str being converted. (In a way, $str is now "tied" to jcode object). $j->set($str [, $icode]) Sets $j's internal string to $str. Handy when you use Jcode object repeatedly (saves time and memory to create object). # converts mailbox to SJIS format my $jconv = new Jcode; $/ = 00; while(&lt;&gt;){ print $jconv->set($_)->mime_decode->sjis; } $j->append($str [, $icode]); Appends $str to $j's internal string. $j = jcode($str [, $icode]); shortcut for Jcode->new() so you can go like; Encoded Strings In general, you can retrieve encoded string as $j->encoded. $sjis = jcode($str)->sjis $euc = $j->euc $jis = $j->jis $sjis = $j->sjis $ucs2 = $j->ucs2 $utf8 = $j->utf8 What you code is what you get :) $iso_2022_jp = $j->iso_2022_jp Same as "$j->h2z->jis". Hankaku Kanas are forcibly converted to Zenkaku. For perl 5.8.1 and better, you can also use any encoding names and aliases that Encode supports. For example: $european = $j->iso_latin1; # replace '-' with '_' for names. FYI: Encode::Encoder uses similar trick. $j->fallback($fallback) For perl is 5.8.1 or better, Jcode stores the internal string in UTF-8. Any character that does not map to ->encoding are replaced with a '?', which is Encode standard. my $unistr = "x{262f}"; # YIN YANG my $j = jcode($unistr); # $j->euc is '?' You can change this behavior by specifying fallback like Encode. Values are the same as Encode. "Jcode::FB_PERLQQ", "Jcode::FB_XML- CREF", "Jcode::FB_HTMLCREF" are aliased to those of Encode for convenice. print $j->fallback(Jcode::FB_PERLQQ)->euc; # 'x{262f}' print $j->fallback(Jcode::FB_XMLCREF)->euc; # '&#x262f;' print $j->fallback(Jcode::FB_HTMLCREF)->euc; # '&#9775;' The global variable $Jcode::FALLBACK stores the default fallback so you can override that by assigning the value. $Jcode::FALLBACK = Jcode::FB_PERLQQ; # set default fallback scheme [@lines =] $jcode->jfold([$width, $newline_str, $kref]) folds lines in jcode string every $width (default: 72) where $width is the number of "halfwidth" character. Fullwidth Characters are counted as two. with a newline string spefied by $newline_str (default: " "). Rudimentary kinsoku suppport is now available for Perl 5.8.1 and better. $length = $jcode->jlength(); returns character length properly, rather than byte length. Methods that use MIME::Base64 To use methods below, you need MIME::Base64. To install, simply perl -MCPAN -e 'CPAN::Shell->install("MIME::Base64")' If your perl is 5.6 or better, there is no need since MIME::Base64 is bundled. $mime_header = $j->mime_encode([$lf, $bpl]) Converts $str to MIME-Header documented in RFC1522. When $lf is specified, it uses $lf to fold line (default: ). When $bpl is speci- fied, it uses $bpl for the number of bytes (default: 76; this number must be smaller than 76). For Perl 5.8.1 or better, you can also encode MIME Header as: $mime_header = $j->MIME_Header; In which case the resulting $mime_header is MIME-B-encoded UTF-8 whereas "$j->mime_encode()" returnes MIME-B-encoded ISO-2022-JP. Most modern MUAs support both. $j->mime_decode; Decodes MIME-Header in Jcode object. For perl 5.8.1 or better, you can also do the same as: Jcode->new($str, 'MIME-Header') Hankaku vs. Zenkaku $j->h2z([$keep_dakuten]) Converts X201 kana (Hankaku) to X208 kana (Zenkaku). When $keep_dakuten is set, it leaves dakuten as is (That is, "ka + dakuten" is left as is instead of being converted to "ga") You can retrieve the number of matches via $j->nmatch; $j->z2h Converts X208 kana (Zenkaku) to X201 kana (Hankaku). You can retrieve the number of matches via $j->nmatch; Regexp emulators To use "->m()" and "->s()", you need perl 5.8.1 or better. $j->tr($from, $to, $opt); Applies "tr/$from/$to/" on Jcode object where $from and $to are EUC-JP strings. On perl 5.8.1 or better, $from and $to can also be flagged UTF-8 strings. If $opt is set, "tr/$from/$to/$opt" is applied. $opt must be 'c', 'd' or the combination thereof. You can retrieve the number of matches via $j->nmatch; The following methods are available only for perl 5.8.1 or better. $j->s($patter, $replace, $opt); Applies "s/$pattern/$replace/$opt". $pattern and "replace" must be in EUC-JP or flagged UTF-8. $opt are the same as regexp options. See perlre for regexp options. Like "$j->tr()", "$j->s()" returns the object itself so you can nest the operation as follows; $j->tr("a-z", "A-Z")->s("foo", "bar"); [@match = ] $j->m($pattern, $opt); Applies "m/$patter/$opt". Note that this method DOES NOT RETURN AN OBJECT so you can't chain the method like "$j->s()". Instance Variables If you need to access instance variables of Jcode object, use access methods below instead of directly accessing them (That's what OOP is all about) FYI, Jcode uses a ref to array instead of ref to hash (common way) to optimize speed (Actually you don't have to know as long as you use access methods instead; Once again, that's OOP) $j->r_str Reference to the EUC-coded String. $j->icode Input charcode in recent operation. $j->nmatch Number of matches (Used in $j->tr, etc.) Subroutines ($code, [$nmatch]) = getcode($str) Returns char code of $str. Return codes are as follows ascii Ascii (Contains no Japanese Code) binary Binary (Not Text File) euc EUC-JP sjis SHIFT_JIS jis JIS (ISO-2022-JP) ucs2 UCS2 (Raw Unicode) utf8 UTF8 When array context is used instead of scaler, it also returns how many character codes are found. As mentioned above, $str can be $str instead. jcode.pl Users: This function is 100% upper-conpatible with jcode::getcode() -- well, almost; * When its return value is an array, the order is the opposite; jcode::getcode() returns $nmatch first. * jcode::getcode() returns 'undef' when the number of EUC characters is equal to that of SJIS. Jcode::getcode() returns EUC. for Jcode.pm there is no in-betweens. Jcode::convert($str, [$ocode, $icode, $opt]) Converts $str to char code specified by $ocode. When $icode is specified also, it assumes $icode for input string instead of the one checked by getcode(). As mentioned above, $str can be $str instead. jcode.pl Users: This function is 100% upper-conpatible with jcode::convert() ! BUGS
For perl is 5.8.1 or later, Jcode acts as a wrapper to Encode. Meaning Jcode is subject to bugs therein. ACKNOWLEDGEMENTS
This package owes a lot in motivation, design, and code, to the jcode.pl for Perl4 by Kazumasa Utashiro <utashiro@iij.ad.jp>. Hiroki Ohzaki <ohzaki@iod.ricoh.co.jp> has helped me polish regexp from the very first stage of development. JEncode by makamaka@donzoko.net has inspired me to integrate Encode to Jcode. He has also contributed Japanese POD. And folks at Jcode Mailing list <jcode5@ring.gr.jp>. Without them, I couldn't have coded this far. SEE ALSO
Encode Jcode::Nihongo <http://www.iana.org/assignments/character-sets> COPYRIGHT
Copyright 1999-2005 Dan Kogai <dankogai@dan.co.jp> This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself. perl v5.8.8 2005-02-19 Jcode(3pm)
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