Symbolic or soft link (files or directories, more flexible and self documenting)

    #     Source                             Link
    ln -s /home/jake/doc/test/2000/something /home/jake/xxx

Hard link (files only, less flexible and not self documenting)

    #   Source                             Link
    ln /home/jake/doc/test/2000/something /home/jake/xxx


More information: [man ln][1]


  [1]: https://www.man7.org/linux/man-pages/man1/ln.1.html
-----

`/home/jake/xxx` is like a new directory. To avoid *&quot;is not a directory: No such file or directory&quot;* error, as @trlkly comment, use relative path in the target, that is, using the example:

1. `cd /home/jake/`
2. `ln -s /home/jake/doc/test/2000/something  xxx`



you should use :

    ln -s /home/jake/doc/test/2000/something xxx

I&#39;m new to parallel programming. There are two classes available in .NET: `Task` and `Thread`. 

So, my questions are:

 * What is the difference between those classes? 
 * When is it better to use `Thread` over `Task` (and vice-versa)?

Task vs Thread differences

From post:

https://stackoverflow.com/questions/2494294/sending-a-json-array-to-be-received-as-a-dictionarystring-string/7196027#7196027

I’m trying to do this same thing as that post. The only issue is that I don’t know what the keys and the values are upfront. So I need to be able to dynamically add the key and value pairs and I don’t know how to do that.

Does anyone know how to create that object and add key value pairs dynamically?

I’ve tried:

    var vars = [{key:&quot;key&quot;, value:&quot;value&quot;}];
    vars[0].key = &quot;newkey&quot;;
    vars[0].value = &quot;newvalue&quot;;

But that doesn’t work.

How to create dictionary and add key–value pairs dynamically?

How to create a link `xxx` to `/home/jake/doc/test/2000/something/`?

Assume the `xxx` is created under `/home/jake` and you&#39;re currently in `/home/jake`. When you do `cd xxx`, you directly go to `/home/jake/doc/test/2000/something/`.

How to create a link to a directory

<p>How to create a link <code>xxx</code> to <code>/home/jake/doc/test/2000/something/</code>?</p>
<p>Assume the <code>xxx</code> is created under <code>/home/jake</code> and you're currently in <code>/home/jake</code>. When you do <code>cd xxx</code>, you directly go to <code>/home/jake/doc/test/2000/something/</code>.</p>


From a bash script how can I quickly find out whether a port `445` is open/listening on a server.

I have tried a couple of options, but I want something quick:  
1. `lsof -i :445`  (Takes seconds)  
2. `netstat -an |grep 445 |grep LISTEN` (Takes seconds)  
3. `telnet` (it doesn&#39;t return)  
4. `nmap`, `netcat` are not available on the server  

It will be nice to know of a way that doesn&#39;t enumerate first and greps after that.


Efficiently test if a port is open on Linux?

I need to copy all `*.jar` files from a directory maintaining the folder structure of the parent directories. How can I do it in UNIX/Linux terminal?  
The command `cp -r *.jar /destination_dir` is not what I am looking for.

Recursive copy of a specific file type maintaining the file structure in Unix/Linux?

Is there a &quot;goto&quot; statement in bash ? I know It is considered bad practice, but I need specifically &quot;goto&quot;.

Is there a &quot;goto&quot; statement in bash?

When I use `exit` command in a shell script, the script will terminate the terminal (the prompt). Is there any way to terminate a script and then staying in the terminal?

My script `run.sh` is expected to execute by directly being sourced, or sourced from another script.

EDIT:
To be more specific, there are two scripts `run2.sh` as

    ...
    . run.sh
    echo &quot;place A&quot;
    ...

and `run.sh` as

    ...
    exit
    ...

when I run it by `. run2.sh`, and if it hit `exit` codeline in `run.sh`, I want it to stop to the terminal and stay there. But using `exit`, the whole terminal gets closed. 

PS: I have tried to use `return`, but `echo` codeline will still gets executed....

Any way to exit bash script, but not quitting the terminal

TCP has the tuple pairs (IP Addr/port/type) to tell one client from another.  UDP passes the client IP and port.  How does the unix domain keep track of different clients?

In other words the server creates a socket bound to some path say /tmp/socket.  2 or more clients connect to /tmp/socket.  What is going on underneath that keeps track of data from client1 and client2?  I imagine the network stack plays no part in domain sockets so is the kernel doing all the work here?

Is there a unix domain protocol format like there is an IP protocol format and TCP/UDP formats?  Is the format of domain socket datagram protocols published somewhere?  Is every unix different or does something like POSIX standardize it?

Thanks for any illumination.  I could not find any information that explained this.  Every source just glossed over how to use the domain sockets.

How do Unix Domain Sockets differentiate between multiple clients?

I prefer to **write solid shell** code, so the errexit &amp; nounset is always set.

The following code will stop at bad_command line

    #!/bin/bash
    set -o errexit
    set -o nounset
    bad_command # stop here
    good_command

I want to capture it, here is my method

    #!/bin/bash
    set -o errexit
    set -o nounset
    rc=1
    bad_command &amp;&amp; rc=0 # stop here
    [ $rc -ne 0 ] &amp;&amp; do_err_handle
    good_command

Is there any better or cleaner method

My Answer:

    #!/bin/bash
    set -o errexit
    set -o nounset
    if ! bad_command ; then
      # error handle here
    fi
    good_command


What is the proper way to detect shell exit code when errexit option is set?

In the linux shell, the following command will recursively search and replace all instances of &#39;this&#39; with &#39;that&#39; (I don&#39;t have a Linux shell in front of me, but it should do).

    find . -name &quot;*.txt&quot; -print | xargs sed -i &#39;s/this/that/g&#39;

What will a similar command on OSX look like?

Recursive search and replace in text files on Mac and Linux

If I have a text file with a separate command on each line how would I make terminal run each line as a command? I just don&#39;t want to have to copy and paste 1 line at a time. It doesn&#39;t HAVE to be a text file... It can be any kind of file that will work.

`example.txt`:
    
    sudo command 1
    sudo command 2
    sudo command 3

Run text file as commands in Bash

I understand it&#39;s off topic, I couldn&#39;t find anywhere online and I was thinking maybe programming gurus in the community might know this.  
I usually use 

    kill -9 pid

to kill the job. I always wondered the origin of 9. I looked it up online, and it says

&quot;9 Means KILL signal that is not catchable or ignorable. In other words it would signal process (some running application) to quit immediately&quot; (source: http://wiki.answers.com/Q/What_does_kill_-9_do_in_unix_in_its_entirety)

But, why 9? and what about the other numbers? is there any historical significance or because of the architecture of Unix?


Why number 9 in kill -9 command in unix?

So I&#39;ve been searching around and cannot find out exactly how to do this.  I&#39;m creating a user control using MVVM and would like to run a command on the &#39;Loaded&#39; event.  I realize this requires a little bit of code behind, but I can&#39;t quite figure out what&#39;s needed.  The command is located in the ViewModel, which is set as the datacontext of the view, but I&#39;m not sure exactly how to route this so I can call it from the code behind of the loaded event.  Basically what I want is something like this...

    private void UserControl_Loaded(object sender, RoutedEventArgs e)
    {
        //Call command from viewmodel
    }

Looking around I can&#39;t seem to find the syntax for this anywhere.  Do I need to bind the command in the xaml first to be able to reference it?  I notice the command bindings option within a user control will not let you bind commands as you can within something like a button...

    &lt;UserControl.CommandBindings&gt;
        &lt;CommandBinding Command=&quot;{Binding MyCommand}&quot; /&gt; &lt;!-- Throws compile error --&gt;
    &lt;/UserControl.CommandBindings&gt;

I&#39;m sure there&#39;s a simple way to do this, but I can&#39;t for the life of me figure it out.  



Call Command from Code Behind

I know how to run a shell command in Ruby like:

    %x[#{cmd}]

But, how do I specify a directory to run this command?

Is there a similar way of shelling out, similar to `subprocess.Popen` in Python:

    subprocess.Popen(r&#39;c:\mytool\tool.exe&#39;, cwd=r&#39;d:\test\local&#39;)


Thanks!


Ruby run shell command in a specific directory

`rm` is to remove item, but what is the parameter `-rf` do or signify?  
___

Whenever I typed help -rf it printed the entire list of available commands in powershell.  What happens if you type rm -rf in powershell? From reading around I&#39;ve gathered that it will delete everything on the drive?  I&#39;m not sure?

Also, is rm -rf same as rm -rf /  

Content Type	Original Author	Original Content on Stackoverflow
Question	read Read	View Question on Stackoverflow
Solution 1 - Linux	theglauber	View Answer on Stackoverflow
Solution 2 - Linux	WiseTechi	View Answer on Stackoverflow

How to create a link to a directory

Linux Problem Overview

Linux Solutions

Solution 1 - Linux

Solution 2 - Linux

How to create dictionary and add key–value pairs dynamically?

Task vs Thread differences

Attributions