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:

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.


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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*/


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General :: Command For Short File Descriptor?

Jun 25, 2010

the short file descriptor of an ISO file. I have been assigned with a task to match the short file descriptor of an ISO file(to be provided to the customer) to check if thats "Kudgo Support tools" or not.What linux command should I use?

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General :: Input To Sudo - What Is Its File Descriptor

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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General :: How To Using Redirection To Create A File

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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General :: Using File Redirection Operators In Bash?

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:


[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

I'm working on some scheduled task script files to keep nightly backups of some of our database information in place, and it's a bit annoying when they blow up. I know how to redirect stdout and stderr to a flat file I can view when I come in, and I know that 2>&1 maps them both to the same file (whatever was named in 1). However, I'm running into some cron-time situations where it's easier to have the two streams together, and other cron-time situations where it's easier to have them separated. I can't really tell which is going to happen; is there some way I could create both kinds of output file for my scripts, so that I've got a std_err only file and an interleaved std_out/std_err file?

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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Programming :: Pyhon - Get The File Descriptor?

Apr 19, 2011

I create two script file name for "" and "", It's through socket connection.'s file writeing ",x)"create the file descriptor,but i don't know how to get the descriptor file with ""

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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$Acceptor run SEVERE: Socket accept failed

at Method)


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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Ubuntu Multimedia :: Starting Jack - Bad File Descriptor

Dec 10, 2010

I am having problems starting jack everytime I try to start it either says bad file descriptor a bunch times or it wont connect to server as client sometime. Other times It just say sorry cannot start jack.

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SUSE :: Get File Descriptor From Major And Minor Number?

Nov 15, 2010

Is it possible to get a file descriptor from the major and minor number. If so, how can this be done? I am trying to see if a port(eg ttyS2) is opened without using the fdopen or open or fopen functions. is there a way to get the file descriptor of file or port that as already been opened, without using the functions I mentioned above. These functions reopens the port. I am trying to avoid that.

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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
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

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Programming :: PyGTK: Send Output From A File Descriptor To A Textview?

Jul 22, 2010

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:

def run_command(command):
global keep_pulsing
(cpid, cstdin, cstdout, cstderr) = gobject.spawn_async(command,flags=gobject.SPAWN_DO_NOT_REAP_CHILD|gobject.SPAWN_STDERR_TO_DEV_NULL,standard_code....

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.

textview = wTree.get_widget('textview1')
def update_textview_callback(fd, condition):
global keep_pulsing
if keep_pulsing:

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Programming :: Redirection From A File To Command?

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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Programming :: File Redirection Does Not Work Bizzare?

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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Programming :: STDIN, STDOUT, STDERROR Redirection For Scripting - Bash: Log.txt: No Such File Or Directory

Sep 7, 2010

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!):


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:


tac < log.txt 2>/dev/null

I get:


bash: log.txt: No such file or directory

The tac error is suppressed but bash still gives me a dirty error.

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General :: How To Stop Redirection To /dev/pts/x

Jul 10, 2010

This is an examination senario. We have mulitple users logging into a RHEL-4 server using putty. These people are part of a same group. They are giving UNIX shell script exam.They are helping each other copy the code by using redirection to /dev/pts/x. Is there any way I can stop this redirection?

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General :: When To Do Port Redirection

Feb 10, 2010

Under what condition port redirection could go useful?

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Ubuntu :: Grub2 Clean Up And Duplication?

Nov 11, 2010

this is my first post here .I have two issues related to grub2 I upgraded recently from ubuntu 8 to 10.04 and upgraded grub 0.98 to 1.98. 1-How to prevent Grub from detecting one of Windows installations? or how does grub detect Windows. I have 2 hdds, they were backup of each other. but no more, I deleted one Windows by deleting most of the files so therefore I don't need it to be present in Grub 2 menu. How do I delete this? any suggestion? 2-For some reason grub2 only work correctly from sdb , even though I chose to install grub2 to sda too, but it seems grub is trying to find grub files on the same hard disk instead of on sdb, therefore it goes into grub rescue mode with error "file not found" . I set my computer to boot from sdb for now. but I would like to learn how to make sda's grub work. before it used to work with grub 0.98.

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Ubuntu :: Disk Duplication To Work On Another Machine?

May 6, 2010

cant I simply take a working ubuntu hard drive and dd copy it onto another disk. Then put the disk in the other pc and it will work?

This way I could configure a machine at home, take the disk with me and use it at a place with no internet access.

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General :: Rdesktop USB-redirection Save Removal?

May 16, 2011

We have several HP Thin-Clients of type t5545 in use. We redirect USB-Media to the terminalserver. Because the t5545 runs a debian customized by hp, we can treat it like a debian in some way.First, I'll explain how usb-redirection is configured: automatically mount it to /tmp/tmpfs/media /tmp/tmpfs/media is redirected as disk "Z" via rdesktop-parameter -r disk:sharename=path in case of removed usb-media udev will run a script to umount -l the device and delete the mountpointThe environment:

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
Terminalserver runs Windows Server 2008 R2


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General :: Printf Calls - Cost Of I / O Redirection

Dec 16, 2010

Some context: I'm calling some functions from within a C program and want to measure how long they take to execute. I've done this successfully, calling printf to print the results to the screen. This is reasonably fast. Ideally I'd like these to be dumped to a file, but fprintf presumably has some overhead since it writes to disk? Unless the data is buffered by the kernel and flushed later? What kind of delay can I expect before fprintf returns?

If I redirect the stdout to a file when I instantiate the binary as a process, will calls to printf also experience any overhead from redirection to a file? My aim here is to capture all data in a file, with the minimal amount of coding and effort, but with minimal impact in terms of time overheads for printf calls.

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Software :: RHEL 6 W/LVM Volume Duplication Breaks Multipathing?

Mar 9, 2011

We're trying to take an existing system running multipathed SAN boot disks, duplicate that boot disk to another system volume, and boot a second system up with all the same parts running like the first system (think: cloning the system).However, multipathing is broke on the second system 'm sure I'm forgetting something stupid here after thecloning).Details:We have a freshly installed RHEL6 on IBM PPCThis is a boot off of a SAN volume with two paths. Installation went great - multipathing was auto-detected and used underneath the usual LVMs for the boot volumes. Looks and works great:

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


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Programming :: UDP Packet Loss - Out Of Sequence - Duplication Simulator ?

Oct 13, 2010

I'm beginning to write a custom RTP implementation and want to test its resilience to UDP traffic. I've searched on the web and all the links I can find are for analysing actual traffic, not generating it or messing it up.

Does anyone know of any software (preferably free software) that will, for example, take actual UDP traffic and drop packets, duplicate some and make some arrive late/out of sequence?

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General :: Redirection Of Private Network Packets In The Gateway

Jul 25, 2011

I have users using Windows XP, Windows 7, Linux (Fedora) and Mac. They all are in a single private network and all access internet through a Linux (RHEL5) system in which Squid acts as gateway. The same is true with my branch offices too except that private network is different and gateway system uses Fedora 9 instead of RHEL5. All the branch offices are connected through point to point leased lines with the head office for file transfer.

My requirement is this: I have a web server located at head office. Presently I am able to access this server from my branch offices through internet. I would like to access this server from branch offices through leased lines. This too I am able to access if I do routing in users system. The file transfer is taking place through one to one system at two ends by creating static routing in those systems.

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Ubuntu :: KDM And GDM Battle At Startup - Both Launch X Servers - Remove Duplication?

Apr 28, 2010

I have both ubuntu and kde-desktop installed, and after trying KDM, switched back to GDM which worked fine for a while (although KDE changed my other gnome settings like usplash and cursors which took a while to change back). A day later, though, when I start up my system, the screen flickers a few times then shows me a message that an x-server is already running, so hit no to try loading it on '0' again or yes to try another number.

If I hit no, it will briefly show me the KDE login screen refresh a few times and go back to the menu. If I hit yes, it refreshes about 7 times and finally shows the gnome login screen. This process takes a long time and I'm not sure is great for my screen.

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