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Linux Distributions

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A Linux distribution is an operating system made as a software collection based on the Linux kernel and, often, on a package management system and are available for a variety of systems. A typical Linux distribution comprises a Linux kernel, GNU tools and libraries, additional software, documentation, a window system (the most common being the X Window System), a window manager, and a desktop environment. Most Linux systems are open-source software made available both as compiled binaries and in source code form, allowing modifications to the original software. Over three hundred distributions are in active development, including commercially backed distributions (such as Fedora, openSUSE and Ubuntu) and community-driven distributions (such as Debian, Slackware, Gentoo and Arch Linux).

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Hi,

With both of the versions of Ubuntu is there a way I can make the favourites bar icons larger. I have found a way to make the other icons larger but not the favourates bar ones.
Happy if there a different way for each version.

Ubuntu 18.04.1 LTS and Ubuntu 18.10

Thanks,

Ward.
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Become a CompTIA Certified Healthcare IT Tech
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Become a CompTIA Certified Healthcare IT Tech

This course will help prep you to earn the CompTIA Healthcare IT Technician certification showing that you have the knowledge and skills needed to succeed in installing, managing, and troubleshooting IT systems in medical and clinical settings.

Dear Experts, I'm testing Oracle 11g on Centos 7 64b.

I installed Oracle but could not connect to the globalDB by sqlplus, it keeps showing error: ORA-12514: TNS:listener does not currently know of service requested in connect even I start the Oracle Database

ora1.PNG
ora2.PNG
I also attached the response file from Installation process. These are the details of listener and tnsname files:

ora3.PNG
lsnrctl status:

ora4.PNG
Can you please help? Many thanks!
db.rsp
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zgrep 'xyz'  abc.log.2018111212| grep '|[1-9][0-9][0-9][0-9][0-9]|0000' | wc -l

i am trying to figure out what above grep doing?

what is meaning of
|[1-9][0-9][0-9][0-9][0-9]|0000

wc -l means some kind of word count?
what is -l

any good links or resources or video tutorials to master greps and awk and sed end to end to debug server logs?

please advise
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Hi

My redhat (guest OS) having issue for not able to resolve the hostname like google.com but able to ping 8.8.8.8.

I didn't do anything at all just to ensure that it can ping Google first and my network subnet like 192.168.1.0/24 when my redhat added a NAT Network adapter without issue.

After that I connect my fortinet vpn client thr IPSec and still can ping and resolve my private cloud thr hostname.

Next day I do the same thing like connect to my iPad 4G network to my Hp laptop wifi.

Can ping and resolved on my hp laptop even being connected to vpn.

The guest os redhat from virtualbox on nat can ping 8.8.8.8 but not able to resolve now.

Why yesterday can and today can't without changing anything?

Thanks.
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For some reason, my server is hitting wp-admin/admin-ajax.php every second.  Even if I close every tab in the browser related to that site it won't stop accessing that url.  I have  narrowed it down to using only one of my ipV6 ip's.  I have tried the code below in functions.php which I put in the child theme's functions.php, did a restart but still it keeps accessing.  I installed Perfmatters and that hasn't stopped it and I installed the Heartbeat Monitor plugin and that hasn't stopped it.

This is taking down my server with that much activity and I can't seem to find a connection since I didn't know this was going on because I hadn't looked at the access_log for several days.  I have resorted to a cron entry to restart apache 2.4 every 5 minutes.

This is the code I tried in the functions.php

*/
add_action( 'init', 'stop_heartbeat', 1 );
function stop_heartbeat() {
 wp_deregister_script('heartbeat');
}
/**

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I am on Linux 2 with Wordpress 4.9.8.

Please help me get this stopped.

Thanks,
0
Hello,
I have a FreeBSD and ubuntu server.
I crate a cronjob to execute in specific time. but the command that I do required a full privilege on system... so how I can make the cronjob work with root for example ?
thanks.
0
I am encountering an error when I try to install memcached on a PHP 7 - Linux AWS system.  This is the command I am using that generates the error.
yum install memcached php-pecl-memcache

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This is 1 of 2 errors:
1.
Finished Dependency Resolution
Error: Package: php-pecl-memcache-3.0.8-4.amzn2.x86_64 (amzn2-core)
           Requires: php(api) = 20100412-64

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2.  
Error: Package: php-pecl-memcache-3.0.8-4.amzn2.x86_64 (amzn2-core)
           Requires: php(zend-abi) = 20100525-64

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Please help me with how to finish installing memcached.

Thanks,
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What is the location of  the binary and library postgresql directories installed on docker linux suse 12 sp2 ?
We have this postgres DB installation working ok.
I have access to the database using pgadmin and dbeaver.
But we don't know who did this installation and I need to know the location of the binary and library postgresql directories in order to run pg_ctl and psql.
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For Clam's dependent packages required as indicated by
  https://www.opencsw.org/packages/CSWclamav/  ,

I can't get 2 packages for Solaris 10 (Update 9) x86 :

1. common : it can only locate the i386 package for SunOS 5.8 in url below
  http://rsync.opencsw.org/opencsw/testing/i386/5.10/

Likewise for
2. libbz2_1_0 : can only locate for SunOS 5.9


Anyone has access to Oracle subscription, can assist to download the above
packages & attach them here?


For the 10 dependent packages, what's given are for i386, so if can help
provide for Solaris 10 x86, appreciated:
https://www.opencsw.org/packages/CSWclamav/
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https://www.manageengine.com/products/eventlog/system_requirement.html

We're trying to quickly set up ManageEngine Eventlog analyzer/SIEM for our
Solaris 10 x86   and  RHEL 6  servers : all are 64bit OS.

Somehow I can't locate anything for Solaris 10 x86 : need the agents installer.
Still looking for RHEL6.  I'm not too good with navigating.

Anyone can help locate & give the exact links?
0
Learn Ruby Fundamentals
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Learn Ruby Fundamentals

This course will introduce you to Ruby, as well as teach you about classes, methods, variables, data structures, loops, enumerable methods, and finishing touches.

xhost executing successfully for the user who has the direct login access to the OS.

when I swtich to the other user (su) and which doesn't have the direct login access to OS, could not run the xhost command.

Kindly advice, how to achieve the same.
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I started with asking what the different is between "mode" and "flag", see: https://www.experts-exchange.com/questions/29122213/What-is-the-difference-between-mode-and-flag.html

However, I see that people are using different definitions for a flag. So it's better to start with the question: what is the definition of a flag? I'm not asking for general definitions, or your own definition, but specifically use the definitions in this post (and if necessary correct them and tell me what's wrong about the existing definition).

See: https://techterms.com/definition/flag

In computer science, a flag is a value that acts as a signal for a function or process. The value of the flag is used to determine the next step of a program. Flags are often binary flags, which contain a boolean value (true or false). However, not all flags are binary, meaning they can store a range of values.

Let's start with:

a flag is a value

So apparently, according to this definition, a flag IS a value. So a flag can not be seen as something that be two different values (two different states).

The next sentence confirms that:

Flags are often binary flags, which contain a boolean value (true or false).

Let's say we have c++ std::bitset, but it's about 1 bit. Firstable, it's important to be aware of the difference between:

1. setting the flag
2. setting the bitset

The bitset can be 1 or 0  (in this case because we have one …
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When it's about "flags", I've noticed that different people have different ideas of what a flag is. Some people start to talk about "bit set" when it's about flags. I think the problem lies with the underlaying definitions. It looks like things are not well defined. So for this question, forget about your own ideas/definitions of what a bit set is, just follow the definitions in this post (and change them if necessary). Also forget about flags, this post is specifically about "bitset". First let's start with some "definitions":

See: http://www.cplusplus.com/reference/bitset/bitset/ (std::bitset)

A bitset stores bits (elements with only two possible values: 0 or 1, true or false, ...).

And see: http://www.cplusplus.com/reference/bitset/bitset/set/ (std::bitset::set)

all bits (1)      
bitset& set();
single bit (2)      
bitset& set (size_t pos, bool val = true);

(1) all bits
Sets (to one) all bits in the bitset.
(2) single bit
Sets val as the value for the bit at position pos.

I understand this. But now first let's start at the beginning and let's define a "bit". Let's define it like this:

A bit is an element of two possible binary values: either 0 or 1.

So let's see a bit as a box that contains a ball or a box that doesn't contain a ball. Now let's take a look at a bitset that represents the number 4:

 -----------------------
|0     | 0     |  1     |
|0*2^0 | 0*2^1 |  1*2^2 |
 -----------------------
3 boxes: 
Box 1: no ball
Box 2: no ball
Box 3: ball

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Our RHEL 6  DB server does not have Internet access, thus we can't do 'yum'.

We would like to temporarily install ftp server (guess it's called vsftpd) :
how can we go about doing this?  Give step by step instruction including
where to get vsftpd rpm package (& its dependent packages if any).

Also provide the exact commands (guess it's  'rpm -ivh ./folder_of_RPMs' )

We can download to a laptop & use laptop to sftp over the RPMs.
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In short, I would say:

A flag is a predefined bit or bit sequence that holds a binary value.

A mode is a distinct setting.

So it's not always possible to replace the term "mode" by "flag". This is only possible if it's about a binary value. I got confused by these terms when reading:

http://man7.org/linux/man-pages/man2/open.2.html

The argument flags must include one of the following access modes:
O_RDONLY, O_WRONLY, or O_RDWR.

The file creation flags are O_CLOEXEC,
O_CREAT, O_DIRECTORY, O_EXCL, O_NOCTTY, O_NOFOLLOW, O_TMPFILE, and
O_TRUNC.

The file status flags are all of the remaining flags listed
below.

Why they just don't say:

The file access flags are O_RDONLY, O_WRONLY, and O_RDWR.

Why they suddenly use a different term when it's about "access"? Probably behind the scenes it's also just about a binary value, right? Probably all O_VARIABLE's above are 0 or 1.

And see: https://en.wikipedia.org/wiki/File_descriptor

This table records the mode with which the file (or other resource) has been opened: for reading, writing, appending, and possibly other modes.

So Wikipedia uses the term "mode" only (and not flag). At least they are consistent, because they call them all "modes".

Is there a specific reason why sometimes mode is used and something flag (while it's about the same thing)? I would stay, be at least consistent to avoid confusion.
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In reality, the "open file table" is not really a table, but let's say we will see it as a table. Which columns does this table have?

For example, see: https://cseweb.ucsd.edu/classes/sp16/cse120-a/applications/ln/lecture15.html

The open file table contains several pieces of information about each file:

the current offset (the next position to be accessed in the file)
a reference count (we'll explain below in the section about fork())
the file mode (permissions),
the flags passed into the open() (read-only, write-only, create, &c),
a pointer to an in-RAM version of the inode (a slightly light-weight version of the inode for each open file is kept in RAM -- others are on disk), and a structure that contains pointers to all of the .
A pointer to the structure containing pointers to the functions that implement the behaviors like read(), write(), close(), lseek(), &c on the file system that contains this file. This is the same structure we looked at last week when we discussed the file system interface to I/O devices.

So according to this, I would say:

- offset
- reference count
- file mode (permission)
- the flags passed into the open() (read-only, write-only, create, &c),
- pointer to in-RAM inode
- pointer to "read(), write(), close(), lseek(), &c".

But the file descriptor also points to the open file table, so we need another column that connects the "file descriptor table" with the "open file table". So I would add a column like:
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Actually the file descriptor table is not a real table. It's just an array of pointers to the "open file table" (struct file). But let's say we will see it as a table. What are the columns? For example:

FD   | Pointer to "open file table"
----------------------------------
...  | ...

In short, that's the question. I see a lot of different figures on the internet, but they are all different. For example, see:

http://faculty.winthrop.edu/dannellys/csci325/10_shared.htm
There they have a column "fd flags" (read/write), but I would think that this column is part of the "open file table" and not part of the "file descriptor table". See for example: http://man7.org/linux/man-pages/man2/open.2.html


       A call to open() creates a new open file description, an entry in the
       system-wide table of open files.  The open file description records
       the file offset and the file status flags (see below).  A file
       descriptor is a reference to an open file description; this reference
       is unaffected if pathname is subsequently removed or modified to
       refer to a different file.  For further details on open file
       descriptions, see NOTES.

       The argument flags must include one of the following access modes:
       O_RDONLY, O_WRONLY, or O_RDWR.  These request opening the file read-
       only, write-only, or read/write, respectively.
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I get a black screen when I am trying to install Manjaro 17 from USB onto my Asus tower, G20aj Processor Intel® Core™ i5-4460 CPU @ 3.20GHz, 3201 Mhz, 4 Core(s), 4 Logical Processor(s). . ( had the same issue in Ubuntu, but thought the different loader Manjaro and Arch might make a difference but it hasn’t.)  The problem seems to lie with the Asus video drivers as I can install just fine on my Alienware/Dell and my HP Spectre.
On the Ubuntu side I found posts talking about some commands to run to get around this issue like aspci and quiet splash, etc. I am not sure where to enter commands or how.  

What I have been doing is boot the computer with install USB and go to the Manjaro OS install line press “e” and then go to the line beginning “Linux/boot/vmlinux-$2” at the end of that line place my commands like  acpi_enforce_resources=lax acpi_osi=Linux acpi_osi=’!Windows 2012’ acpi=force pcie_aspm=force
and then hit F10?

Nothing seems to work.  I have been working on the Manjaro forum but have come to a bit of deadend.
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unix server keep sign out after 1 minute or so on production.

is there is a way i can run some process like

tail -f xyz.gz
to keep continuous rolling until i cancel that so that it wont sign out on me while i focus on some other work  for 30 miinutes and come back it should not signout
please advise
0
Exploring SharePoint 2016
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Exploring SharePoint 2016

Explore SharePoint 2016, the web-based, collaborative platform that integrates with Microsoft Office to provide intranets, secure document management, and collaboration so you can develop your online and offline capabilities.

Let's start with a useless example of input redirection:

less 1< /test.txt

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The result is:

Missing filename ("less --help" for help)

This I understand, because:

LESS-PROCESS:
FD 0 <- terminal file (keyboard)
FD 1 <- /test.txt
FD 2 -> terminal file (monitor)

FD 0 needs to get some content from a file, but there is no file in this case. There is /test.txt but it points to the wrong fd. Now let's take a look at a useless example of output redirection:

less 0> /test.txt

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LESS-PROCESS:
FD 0 -> /test.txt
FD 1 -> terminal file (monitor)
FD 2 -> terminal file (monitor)

The program doesn't give file descriptor 0 some output, so "nothing" will be written to /test.txt. That why you will always end up with an empty /test.txt file. File descriptor 0 opens /test.txt for writing and not for reading. So the less-process doesn't get any file to read from. Then why the result is not:

Missing filename ("less --help" for help)

Instead, less is acting as it got an empty file as input. The file /test.txt is empty in the end, but this is about output redirection and not about input redirection, so there is no input. That's the reason why I would expect "Missing filename". Why this is not the case?
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See: https://stackoverflow.com/questions/6170598/can-anyone-explain-to-me-what-the-purpose-of-dev-tty


You can start with the POSIX spec. From there, read about the "controlling terminal" of a process.

But just for example... /dev/tty is how a command like "ssh" can read your password even if its standard input comes from somewhere else:

tar cf - . | ssh dest 'tar xf -'

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If ssh decides to prompt you for a password, it will read it from /dev/tty instead of stdin.

Conceptually, /dev/tty is "the keyboard and text terminal". More or less.

Let's say my "terminal-file" of the current session is /dev/pts/1. In such a case, then what's the difference between "/dev/pts/1" and "/dev/tty"? And if they are basically the same, then why  "/dev/tty" is used instead of "/dev/pts/1"?

And:

/dev/tty is how a command like "ssh" can read your password even if its standard input comes from somewhere else

Let's say the standard input comes from somewhere else, so let's say we have:

FD 0 <- file
FD 1 -> /dev/pts/1
FD 2 -> /dev/pts/1

How I see it: the fact that the standard input comes from somewhere else doesn't mean that /dev/pts/1 can not be read? The password comes from the keyboard and /dev/pts/1 represents i.a. the keyboard, right? So I still don't see what exactly the purpose is of /dev/tty?

@noci: I know you know the answer, but I don't understand your explanation so I've made this post so maybe other people can explain it to me in a way that I understand it.
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I'm reading about "redirection of input" on the internet. I understand what's behind it. For example:

command < file.ext

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This is equivalent to:

command 0< file.ext

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In general, if you have:

command n< file.ext

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then the contents of file.ext go to file descriptor "n" as input. I've checked different websites explaining "input redirection". However, the problem is that I didn't see any good example. I'll discuss some examples I saw:

cat < file.txt

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Then I'm thinking, "cat file.txt" does the same, so why do we need it? Another example:

sort < file_list.txt > sorted_file_list.txt

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Then I'm thinking, "sort file_list.txt > sorted_file_list.txt" does the same, so why do we need it? Another example:

more < /etc/passwd

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Then I'm thinking, "more /etc/passwd" does the same, so why do we need it? That's why these are not really good examples in my opinion. What is a good example to explain the purpose of input redirection in a terminal-window?

Probably internally something like "cat file.txt" is being treated as "cat 0< file.txt" (input redirection), but in a terminal-window ... when it really does make sense to use an "input redirection" in a terminal-window? Does someone have a good example?
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First I create a regular file with some contents (manual page of find command):

man find > test.txt

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Then I use the less command to display some of these contents:

less test.txt

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Now I press CTRL-Z to suspend the process. The process is still open, so now I can execute this command:

lsof | grep 'less'

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By doing this, I get an idea which files are open with respect to the less-process. My result:

COMMAND  PID    USER  FD   TYPE  DEVICE  SIZE/OFF  NODE       NAME
less     24565  root  cwd  DIR   0,38    4096      21473055   /
less     24565  root  rtd  DIR   0,38    4096      21473055   /
less     24565  root  txt  REG   0,38    149944    22143102   /usr/bin/less
less     24565  root  mem  REG   9,1               22143102   /usr/bin/less (path dev=0,38)
less     24565  root  mem  REG   9,1               22135172   /usr/lib/locale/locale-archive-rpm (path dev=0,38)
less     24565  root  mem  REG   9,1               21741879   /lib64/libc-2.12.so (path dev=0,38)
less     24565  root  mem  REG   9,1               22265955   /usr/local/lib/libpcre.so.0.0.1 (path dev=0,38)
less     24565  root  mem  REG   9,1               21741743   /lib64/libtinfo.so.5.7 (path dev=0,38)
less     24565  root  mem  REG   9,1               21741946   /lib64/ld-2.12.so (path dev=0,38)
less     24565  root  0u   CHR   136,1   0t0       4          /dev/pts/1
less     24565  root  1u   CHR   136,1   0t0       4          /dev/pts/1
less     

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Let's say I type the following "in a terminal":

echo 'bla'

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In my case, the shell is bash, so I assume the shell/bash-process receives "echo 'bla'" as standard input? Then it sees "echo", so a child process will be started. So then we will have at least:

ECHO PROCESS:
fd 0 (standard input)   <- terminal-file (keyboard)
fd 1 (standard output)  -> terminal-file (monitor)
fd 2 (standard error)   -> terminal-file (monitor)

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I thought that for this process, only "bla" is the standard input. And then the output is also "bla", so I'll see "bla" on my monitor.

I was just a bit playing with "input redirections" and I noticed that the following does not work:

echo < bla-file.txt

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After some Google searches, I found out that "echo" does not read from stdin. However, it prints all of its arguments. So it's working differently than normal. So how I have to see/change this:

ECHO PROCESS:
fd 0 (standard input)   <- terminal-file (keyboard)
fd 1 (standard output)  -> terminal-file (monitor)
fd 2 (standard error)   -> terminal-file (monitor)

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I thought every process by default has fd's 0,1,2? But if fd 0 would be there something like this:

fd 0 (standard input)   <- nothing

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Then it should be still possible to redirect (input) to something. So this means I can not see it like that. Does this mean that the echo process doesn't have a fd 0 at all? Or I must not see "echo" as a process with a fd table et cetera?

But the echo command displays something on my monitor, so at least this should be there:

fd 1 (standard output)  -> terminal-file (monitor)

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1
Redirecting output ([n]>[|]word), when does "n" greater than 2 make sense?

This question is about redirecting output in bash, see: https://www.gnu.org/software/bash/manual/html_node/Redirections.html#Redirecting-Output

The general format for redirecting output is:

[n]>[|]word

I already understand the basics (you're just redirecting a file descriptor to a file for writing). But, can someone give me an example when it does make sense to use for example: 3>. In other words, if n is greater than stdin, stdout, stderr (>2), for what would you need it?

I can do:

echo 'test' 3> test-file.txt

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This will not write anything to "test-file.txt". This is logical, because now there is just a file descriptor with number 3 pointing to test-file.txt for writing, but there is no input to fd=3 so there is also nothing to write.

The only way to give it some input is to connect file descriptor 3 for reading with a file (or connect it to the output of a pipe). But if you would do that, then fd 3 doesn't point to test-file.txt anymore. So then in the end, fd 3 was connected to test-file.txt without any reason.

So in what kind of situation it's useful to use >n with n greater than 2?
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Linux Distributions

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Solutions

20K

Contributors

A Linux distribution is an operating system made as a software collection based on the Linux kernel and, often, on a package management system and are available for a variety of systems. A typical Linux distribution comprises a Linux kernel, GNU tools and libraries, additional software, documentation, a window system (the most common being the X Window System), a window manager, and a desktop environment. Most Linux systems are open-source software made available both as compiled binaries and in source code form, allowing modifications to the original software. Over three hundred distributions are in active development, including commercially backed distributions (such as Fedora, openSUSE and Ubuntu) and community-driven distributions (such as Debian, Slackware, Gentoo and Arch Linux).