Sponsored Content
Top Forums Shell Programming and Scripting Pipes with the < and >> meanings. Post 302517768 by mirni on Wednesday 27th of April 2011 05:24:08 PM
Old 04-27-2011
That's awesome, thank you!
Although I've been using parameter expansion ${var%pat} quite a bit, the pound and percent I've been confusing all along. The mnemonic is great!
One think that I have yet to be explained is the redirection from subshell in this manner:
Code:
$ while read i ; do echo i $i ; done <(echo blah | sed 's/la/LA/')
bash: syntax error near unexpected token `<(echo blah | sed 's/la/LA/')'

But the following works:
Code:
$ while read i ; do echo i $i ; done < <(echo blah | sed 's/la/LA/')
i bLAh

Why do I need two '<' in this construct?
 

10 More Discussions You Might Find Interesting

1. Filesystems, Disks and Memory

PIPEs and Named PIPEs (FIFO) Buffer size

Hello! How I can increase or decrease predefined pipe buffer size? System FreeBSD 4.9 and RedHat Linux 9.0 Thanks! (1 Reply)
Discussion started by: Jus
1 Replies

2. Shell Programming and Scripting

cd using pipes

Hi, Can the cd command be invoked using pipes??? My actual question is slightly different. I am trying to run an executable from different folders and the path of these folders are obtained dynamically from the front end. Is there a way in which i can actually run the executable... (2 Replies)
Discussion started by: Sinbad
2 Replies

3. Shell Programming and Scripting

where can I get exit code meanings?

I'm investigating strange behaviour on two boxes (Sun OS 5.10 and AIX 5.1) in ksh have used $? to get exit codes returned:- 137 and 34 where can I find what these mean? thank you (1 Reply)
Discussion started by: speedieB
1 Replies

4. Shell Programming and Scripting

named pipes

How to have a conversation between 2 processes using named pipes? (5 Replies)
Discussion started by: kanchan_agr
5 Replies

5. Cybersecurity

Syslog events meanings

Hi everybody, I'm writing to know what the following event stands for. I know that the following event is about a "su to root" action but I don't have any Idea about what action could rise this message. For example If an acction performed by the root crontab, a sudo command or something like that.... (1 Reply)
Discussion started by: PVelazco
1 Replies

6. Shell Programming and Scripting

Pipes not working

Hi, thanks for b4. can anyone tell me why following not working: noUsers=$(who | cut -d" " -f1 | wc -l) What i'm trying to do is get a list of logged on users and pass it to 'wc -l' and store the output to a variable. Any ideas? (1 Reply)
Discussion started by: Furqan_79
1 Replies

7. UNIX for Dummies Questions & Answers

learning about pipes!

im trying to figure out how to do the following: using pipes to combine grep and find commands to print all lines in files that start with the letter f in the current directory that contain the word "test" for example? again using pipes to combine grep and find command, how can I print all... (1 Reply)
Discussion started by: ez45
1 Replies

8. Shell Programming and Scripting

need meanings for FTP codes

Hi Friends, Could i get the meaning for the following FTP codes? 421 425 426 530 450 550 451 551 452 552 553 Thanks, Raja. (1 Reply)
Discussion started by: smr_rashmy
1 Replies

9. Programming

Pipes in C

Hello all, I am trying to learn more about programming Unix pipes in C. I have created a pipe that does od -bc < myfile | head Now, I am trying to create od -bc < myfile | head | wc Here is my code, and I know I might be off, thats why I am here so I can get some clarification. #include... (1 Reply)
Discussion started by: petrca
1 Replies

10. UNIX for Dummies Questions & Answers

top command: abbrevations and meanings - Please !

Hi all, I was trying see some CPU utilization of a Red hat Linux machine using 'top' command. Any way I got high level idea from the out puts, but when I observed the following line: Cpu(s): 7.4%us, 0.5%sy, 0.0%ni, 91.6%id, 0.4%wa, 0.0%hi, 0.1%si, 0.0%st I couldn't make out what... (2 Replies)
Discussion started by: a99u
2 Replies
Data::Dumper::Concise::Sugar(3) 			User Contributed Perl Documentation			   Data::Dumper::Concise::Sugar(3)

NAME
Data::Dumper::Concise::Sugar - return Dwarn @return_value SYNOPSIS
use Data::Dumper::Concise::Sugar; return Dwarn some_call(...) is equivalent to: use Data::Dumper::Concise; if (wantarray) { my @return = some_call(...); warn Dumper(@return); return @return; } else { my $return = some_call(...); warn Dumper($return); return $return; } but shorter. If you need to force scalar context on the value, use Data::Dumper::Concise::Sugar; return DwarnS some_call(...) is equivalent to: use Data::Dumper::Concise; my $return = some_call(...); warn Dumper($return); return $return; If you need to force list context on the value, use Data::Dumper::Concise::Sugar; return DwarnL some_call(...) is equivalent to: use Data::Dumper::Concise; my @return = some_call(...); warn Dumper(@return); return @return; If you want to label your output, try DwarnN use Data::Dumper::Concise::Sugar; return DwarnN $foo is equivalent to: use Data::Dumper::Concise; my @return = some_call(...); warn '$foo => ' . Dumper(@return); return @return; If you want to output a reference returned by a method easily, try $Dwarn $foo->bar->{baz}->$Dwarn is equivalent to: my $return = $foo->bar->{baz}; warn Dumper($return); return $return; If you want to format the output of your data structures, try DwarnF my ($a, $c) = DwarnF { "awesome: $_[0] not awesome: $_[1]" } $awesome, $cheesy; is equivalent to: my @return = ($awesome, $cheesy); warn DumperF { "awesome: $_[0] not awesome: $_[1]" } $awesome, $cheesy; return @return; If you want to immediately die after outputting the data structure, every Dwarn subroutine has a paired Ddie version, so just replace the warn with die. For example: DdieL 'foo', { bar => 'baz' }; DESCRIPTION
use Data::Dumper::Concise::Sugar; will import Dwarn, $Dwarn, DwarnL, DwarnN, and DwarnS into your namespace. Using Exporter, so see its docs for ways to make it do something else. Dwarn sub Dwarn { return DwarnL(@_) if wantarray; DwarnS($_[0]) } $Dwarn $Dwarn = &Dwarn $DwarnN $DwarnN = &DwarnN DwarnL sub Dwarn { warn Data::Dumper::Concise::Dumper @_; @_ } DwarnS sub DwarnS ($) { warn Data::Dumper::Concise::Dumper $_[0]; $_[0] } DwarnN sub DwarnN { warn '$argname => ' . Data::Dumper::Concise::Dumper $_[0]; $_[0] } Note: this requires Devel::ArgNames to be installed. DwarnF sub DwarnF (&@) { my $c = shift; warn &Data::Dumper::Concise::DumperF($c, @_); @_ } TIPS AND TRICKS
global usage Instead of always just doing: use Data::Dumper::Concise::Sugar; Dwarn ... We tend to do: perl -MData::Dumper::Concise::Sugar foo.pl (and then in the perl code:) ::Dwarn ... That way, if you leave them in and run without the "use Data::Dumper::Concise::Sugar" the program will fail to compile and you are less likely to check it in by accident. Furthmore it allows that much less friction to add debug messages. method chaining One trick which is useful when doing method chaining is the following: my $foo = Bar->new; $foo->bar->baz->Data::Dumper::Concise::Sugar::DwarnS->biff; which is the same as: my $foo = Bar->new; (DwarnS $foo->bar->baz)->biff; SEE ALSO
You probably want Devel::Dwarn, it's the shorter name for this module. perl v5.16.2 2011-01-20 Data::Dumper::Concise::Sugar(3)
All times are GMT -4. The time now is 06:01 PM.
Unix & Linux Forums Content Copyright 1993-2022. All Rights Reserved.
Privacy Policy