General :: File Descriptor Redirection And Duplication?

Mar 3, 2010

i've checked the link, and it makes it better. but it doesn't include all the information. i'll continue searching the internet. However i have seen an example of creating a fd:

Code:
exec 5<&1
echo "TEST" >&5
exec 5>&-

as in the page, this was intended to redirect the stdout to the fd 5 and create it, and close it. i have the following questions:- what is exactly the meaning of second command? is it to redirect the command stdout "test" to the fd 5? and how i can see the contents of the fd 5? - in the first command, why the < is used instead if > and what is the difference between the below two commands as in the info bash *Redirection section It will be helpful if anyone could include a graph for file descriptor before and after different command execution.

[Code]...

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General :: Open Local File Error When Creating File Descriptor?

Sep 14, 2009

error message when I ran my program that I couldn't open my local file. I have two files first one is called client, second one is called server I am using named pipes to sent a message from client to the other file called server in client I used mknod() to create the two named pipes,one for read,one for write and created new thread in client using fork() spawned a child process that executed the server file both named pipes are opened the client file got the message from the user and sent it through the named pipes to the server file when the server receives the message , it needs to verfify it is correct in the server file, a local file descriptor is created to read and send this verifing message when it is not correct but I am getting an OPEN() error when I tried to open this shared local array buff and attach it to a file descriptor where the message is kept why do I get this error in server file

int main()
{
/*both named pipes are open*/
rfd=open(IFIO1,0);
wfd=open(IFIO2,1);

[code]....

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Jun 25, 2010

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Aug 5, 2011

Where does input to sudo go? I mean when we give password to sudo prompt where it actually goes? If it goes to a file what is its name or what is its file descriptor?

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May 15, 2011

I have a linux script that generates a string and prints it to the console. I want this string to be the name of a file and open it for editing in vi. How can this be done?

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Sep 3, 2010

What's the difference between using > and >>? How can I use both < and > (redirection operators) in a single command?

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Software :: Perl - Statistics For Duplication File Contents?

Oct 23, 2009

I got a folder containing 20,0000 files (and will be more later), each of this file contains a single URL. What I am trying to do is to do statistics on number of duplicated URLs (file with same content) accumulated, say, from September to October by each day. For example, if file A was created in Sep 1st has a same content with file B created in Sep 15th, then we add 1 to number of duplication on Sep 15th (not Sep 1st). Currently I got a way to do it (in perl) as below:

(1) Read all files inside the folder, print out file content, and modified time into a big file in the format:

Code:

[URL] [month] [day]

(2) Sort the file by month then by day

(3) Then Create two hash : date and content

And then read url from each line into a hash 'content' from the big file (key is url, value left undef), for each new read url found in hash 'content', a duplication is detected, so mark '$date{$month.$day}++' The algorithm could be working but may take too long... so I am wondering if there is some easier way to do that besides hashes.

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General :: File Output Redirection - Redirect Stream To Multiple Files?

Dec 7, 2010

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Note: I've looked at the 'tee' command, but I don't think it will work for what I'm after. 'tee' appears to only work with stdout; I'm trying to work with stderr.

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Programming :: Get File Descriptor Of An Already Opened File?

Jul 20, 2011

Is there any method to get the file descriptor of a file which is already opened by some other process?

Or any method to get the File descriptor from the filepath ?

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Apr 19, 2011

I create two script file name for "a.py" and "b.py", It's through socket connection.
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Programming :: What Does Closing A File Descriptor Mean

Mar 13, 2011

As we know, every process has a table with a file descriptor table, in which each entry contains a file pointer pointing to the corresponding file table which contains a v-node pointer pointing to the v-node table.

When closing a file descriptor, are all these data structure deleted?

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Server :: Can Define Max Limit Of File Descriptor

Jul 7, 2009

We are facing problem of to many file open error because of that application become slow and in tomcat catalina log we get following error frequently Jul 6, 2009 12:27:57 PM org.apache.tomcat.util.net.JIoEndpoint$Acceptor run SEVERE: Socket accept failed

at java.net.PlainSocketImpl.socketAccept(Native Method)
at java.net.PlainSocketImpl.accept(PlainSocketImpl.java:384)
at java.net.ServerSocket.implAccept(ServerSocket.java:453)

[code].....

no file limit,file descriptor limit for 300 user of tomcat application server and also oracle database server?

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Software :: Bad Tty & File Descriptor Error While Building RPM On F13

Dec 20, 2010

I have an FC13 x86_64 server and having trouble building RPMs, but I don't think it's specifically an RPM problem. I think it's a tty management or other type of problem.

When spec files have a "%files -f filelist.txt", which contains the list of files for the RPM, it calls the /usr/lib/check-files script, which sorts the files that are supposed to be in the RPM and compares them with the files that are in the built RPM before they are packaged.

The trouble is that the sort fails.

Here's the trace from the check-files script:

The above doesn't show that the output from sort is redirected into those /tmp files. The first sort succeeds because it reads data sent by the "find" in the same shell. The second sort fails because (I think) it cannot read data from stdin for some reason.

What could possibly cause this? I've checked various permissions, libraries, even used strace extensively, all of which is inconclusive.

This is one of my test server boxes, so this problem is something that I've caused, but I have no idea what.

libc controls input and output, correct? Could it somehow be a glibc problem, or a devpts problem? I can run a simple command and pipe it to sort with no problem. It appears to only be related to sub-shells.

I also replaced sort with cat and just tried to redirect stdin in that file to a temporary file, and that also fails.

I've tried running it with selinux disabled and that has no effect.

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Nov 15, 2010

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Ubuntu Servers :: Maximum Of 1024 File Descriptor Limit?

May 4, 2011

I'm running nginx for static files and as a proxy server for a comet IM server on ubuntu Jaunty. On high load I'm hitting a limit of 1024 file descriptors. I've tried increasing this limit but still can't pass 1024. Does "more /proc/sys/fs/file-nr" gives me the global count of used file descriptors? Why do I see a maximum of 1024 open file descriptors in /proc/sys/fs/file-nr if this is the global count for the machine and each user should have at least 1024 allowed file descriptors by default? Is there a way to increase the limit while the server is running?

Some relevant info on my server:
sudo more /proc/sys/fs/file-nr
1024038001
sudo sysctl fs.file-max
fs.file-max = 38001
sudo nano /etc/security/limits.conf
...
* hard nofile 30000
* soft nofile 30000

I also added this to /usr/local/nginx/conf/nginx.conf:
worker_rlimit_nofile 10240;
Uncommented the following line in /etc/pam.d/su:
session required pam_limits.so

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Within PyGTK I'm using gobject.spawn_async to launch a bash script. I would like the output of that bash script to be displayed within my application. I have a textview set up to receive the text ...

Here are the commands that launch the program:

Code:
def run_command(command):
global keep_pulsing
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Here are the two callback functions. But like I say ... I have no idea how to get that data from the 'cstdout' file descriptor into a textbuffer.

Code:
### THE FOLLOWING ARE GLOBALS:
textview = wTree.get_widget('textview1')
textbuffer=textview.get_buffer()
def update_textview_callback(fd, condition):
global keep_pulsing
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progressbar.pulse()
code....

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Apr 18, 2011

I am always confused about the redirection operator <Lets say i have a file input.txt that contains one word "hello" without the quotes when i do the following why don't i see any output? $echo < input.txt Secondly, i am slightly confused between input redirection < and pipe | operator. Sometimes they seem to do the same thing. For example i can achieve the output from the above command as follows $ cat input.txt | xargs echo

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Apr 21, 2011

When I execute the following command from the linux command line I get the output I want to the screen

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I'm writing a script to execute bash commands in the PHP CLI. I would like to suppress errors from bash and write my own error message if an error occurs. So far I have this (assuming log.txt doesn't exist!):

Code:

tac log.txt 2>/dev/null

Which works as expected, tac kicks up an error but the error is suppressed, but when I use this:

Code:

tac < log.txt 2>/dev/null

I get:

Code:

bash: log.txt: No such file or directory

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Thin-Clients run linux: root@mac-addr:/tmp/tmpfs/media# uname -a
Linux mac-addr 2.6.26-2-686 1 SMP Wed Nov 4 20:45:37 UTC 2009 i686 GNU/Linux
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[code]....

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Dec 16, 2010

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Code:
[root@goldimage dev]# df -k
Filesystem 1K-blocks Used Available Use% Mounted on

[code]....

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