Login or Register to Ask a Question and Join Our Community

Sponsored Content
Full Discussion: Problem with pipes on infinite streams
Top Forums Shell Programming and Scripting Problem with pipes on infinite streams Post 302407979 by tokland on Saturday 27th of March 2010 12:04:56 PM
Old 03-27-2010
Problem with pipes on infinite streams
Here is an example code that shows the issue I have:

Code:
#!/bin/bash
counter() {
  seq 1000 | while read NUM; do
    echo $NUM
    echo "debug: $NUM" >&2 
    sleep 0.1 # slow it down so we know when this loop really ends
  done
}

counter | grep --line-buffered "[27]" | head -n1

Code:
debug: 1
debug: 2
2
debug: 3
debug: 4
debug: 5
debug: 6
debug: 7

If I understand it correctly, "head" finishes on the first match (as expected), but "grep" is not aware of it until it tries to write the next line (the second match). When it does, it finds out the pipe is closed so it also finishes.

That's normally not a problem, but if you have an infinite input stream containing only one match, it won't never stop. Any solution?
 

10 More Discussions You Might Find Interesting

1. UNIX for Dummies Questions & Answers

STREAMS

Hi Everyone I am building some A Class HP boxes as web proxy servers, have just installed HP-UX 11.00 and am starting to configure one according to our standard build policy. However on the A Class I just happened to place the software depot this error message keeps popping up every 2 mins: ... (1 Reply)
Discussion started by: alwayslearningunix
1 Replies

2. 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

3. UNIX for Dummies Questions & Answers

problem with pipes

I have written the following program. The function of this prog is to read data from a file(source.c) and write into another file(dest.c) using pipes. I have just written a line in the source file.Im able to compile and run the program without errors. But the data is not written onto the other... (2 Replies)
Discussion started by: afser
2 Replies

4. Shell Programming and Scripting

infinite while do loop problem

hi all, this is how my scrip looks like #!/bin/sh bindir='/opt/apps/script/bin' datadir='/opt/apps/script/data' dir='/opt/apps/script' while : ; do ls -1rt /opt/apps/script/data/check.txt*|tail -1 > /dev/null 2>&1 if ;then chmod +rwx $bindir/dummy2.sh ... (8 Replies)
Discussion started by: tententen
8 Replies

5. UNIX for Advanced & Expert Users

problem using pipes with "ls"

Hi all, I tried the following command $ find / -name xyx | ls -l so logically it should show the listing of directory xyz , assuming there's only one instance of xyz . But the above command shows the listing of current directory instead. I got the desired result using it in the... (4 Replies)
Discussion started by: bijeet_sunny
4 Replies

6. Programming

Problem with pipes

problem solved. (1 Reply)
Discussion started by: superfons
1 Replies

7. Shell Programming and Scripting

Problem with call of Java Programm & return code handling & output to several streams.

Hello Everybody, thanks in advance for spending some time in my problem. My problem is this: I want to call a java-Programm out of my shell skript, check if die return code is right, and split the output to the normal output and into a file. The following code doesn't work right, because in... (2 Replies)
Discussion started by: danifunny
2 Replies

8. Programming

please help a problem in client-server ipc message 2 pipes communication simple example

I want to have a message send & receive through 2 half-duplex pipes Flow of data top half pipe stdin--->parent(client) fd1--->pipe1-->child(server) fd1 bottom half pipe child(server) fd2---->pipe2--->parent(client) fd2--->stdout I need to have boundary structed message... (1 Reply)
Discussion started by: ouou
1 Replies

9. Programming

Problem with Pipes => Only works first pipe

Hi! I'm having problems with pipes... I need comunnications with childs processes and parents, but only one child can comunnicate with parent (first child), others childs can't. A brief of code: if(pipe(client1r)<0){ perror("pipe"); } ... (1 Reply)
Discussion started by: serpens11
1 Replies

10. Homework & Coursework Questions

Help with infinite loop problem

1. The problem statement, all variables and given/known data: My problem is an infinite loop when i press any other key other then Y or y in the while loop. what i want it to do is return to the normal script outside of it if pressing N or n or keep asking the same question if its any other... (4 Replies)
Discussion started by: Ren_kun
4 Replies

LEARN ABOUT DEBIAN

net::google::code::atomparser

Net::Google::Code::AtomParser(3pm)			User Contributed Perl Documentation			Net::Google::Code::AtomParser(3pm)

NAME

       Net::Google::Code::AtomParser - AtomParser with a parsing method for gcode

DESCRIPTION

INTERFACE

   new
   parse( $xml_content )
       return( $feed, $entries ), $feed is a hashref like {
	   'title' => 'Issue updates for project net-google-code on Google Code',
	   'id' => 'http://code.google.com/feeds/p/net-google-code/issueupdates/basic',
	   'updated' => '2009-06-12T05:55:48Z' }

       $entries is an arrayref like [
	   {
	       'content' => '<pre>second comment
	</pre>
	',
	       'name'  => 'sunnavy',
	       'title' => 'Update 2 to issue 22 ("for sd test")',
	       'id' => 'http://code.google.com/feeds/p/net-google-code/issueupdates/basic/22/2',
	       'updated' => '2009-06-12T05:55:48Z'
	   },
	   {
	       'content' => '<pre>first comment
	</pre>
	',
	       'name'  => 'sunnavy',
	       'title' => 'Update 1 to issue 22 ("for sd test")',
	       'id' => 'http://code.google.com/feeds/p/net-google-code/issueupdates/basic/22/1',
	       'updated' => '2009-06-12T05:55:22Z'
	   }, ]

AUTHOR

       sunnavy	"<sunnavy@bestpractical.com>"

LICENCE AND COPYRIGHT

       Copyright 2008-2010 Best Practical Solutions.

       This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.

perl v5.10.1							    2010-01-29					Net::Google::Code::AtomParser(3pm)
All times are GMT -4. The time now is 06:02 PM.
Unix & Linux Forums Content Copyright 1993-2022. All Rights Reserved.
Privacy Policy