Sure, just add `&amp;` after the command:

    read_cfg cfgA &amp;
    read_cfg cfgB &amp;
    read_cfg cfgC &amp;
    wait

all those jobs will then run in the background simultaneously. The optional `wait` command will then wait for all the jobs to finish.

Each command will run in a separate process, so it&#39;s technically not &quot;multithreading&quot;, but I believe it solves your problem.

You can run several copies of your script in parallel, each copy for different input data, e.g. to process all *.cfg files on 4 cores:


        ls *.cfg | xargs -P 4 -n 1 read_cfg.sh

The read_cfg.sh script takes just one parameters (as enforced by -n)

Bash job control involves multiple processes, not multiple threads.

You can execute a command in background with the `&amp;` suffix.

You can wait for completion of a background command with the `wait` command.

You can execute multiple commands in parallel by separating them with `|`. This provides also a synchronization mechanism, since stdout of a command at left of `|` is connected to stdin of command at right.



I would like to pass values into the constructor on the class that implements my service.  
 
However ServiceHost only lets me pass in the name of the type to create, not what arguments to pass to its contrstructor.

I would like to be able to pass in a factory that creates my service object.

What I have found so far:

- [WCF Dependency Injection Behavior][1] which is more than what I am looking for and seems to be over-complex for my needs.

  [1]: http://weblogs.asp.net/cibrax/archive/2007/12/13/wcf-dependency-injection-behavior.aspx

How do I pass values to the constructor on my wcf service?

I want to know how and when can I use the `exit()` function like the program in my book:

    #include&lt;stdio.h&gt;
    
    void main()
    {
        int goals;
        printf(&quot;enter number of goals scored&quot;);
        scanf(&quot;%d&quot;,&amp;goals);
    
        if(goals&lt;=5)
            goto sos;
        else
        {
            printf(&quot;hehe&quot;);
            exit( );
        }
        sos:
        printf(&quot;to err is human&quot;);
    }

When I run it, it shows ERROR: *call to undefined function exit()*.

Also, I want to know how I can create an option to close the window in which the program runs? For example, I made a menu-driven program which had several options and one of them was *&quot;exit the menu&quot;*. How can I make this exit the program (i.e. close the window)?

Use of exit() function

I would like to introduce multithreading feature in my shell script.

I have a script which calls the function `read_cfg()` with different arguments.
Each of these function calls are independent.

Would it be possible to instantiate these function calls (not scripts) parallelly.
Please let me how can we achieve that.. ?

Multithreading in Bash

I would like to introduce multithreading feature in my shell script.
I have a script which calls the function <code>read_cfg()</code> with different arguments.
Each of these function calls are independent.
Would it be possible to instantiate these function calls (not scripts) parallelly.
Please let me how can we achieve that.. ?

Is there a MySQL command to locate the `my.cnf` configuration file, similar to how PHP&#39;s `phpinfo()`  locates its `php.ini`?

How do I find the MySQL my.cnf location

I needed to write a script to enter multi-line input to a program (`psql`).

After a bit of googling, I found the following syntax works:

    cat &lt;&lt; EOF | psql ---params
    BEGIN;
    
    `pg_dump ----something`
    
    update table .... statement ...;
    
    END;
    EOF

This correctly constructs the multi-line string (from `BEGIN;` to `END;`, inclusive) and pipes it as an input to `psql`.

But I have no idea how/why it works, can some one please explain?

I&#39;m referring mainly to `cat &lt;&lt; EOF`, I know `&gt;` outputs to a file, `&gt;&gt;` appends to a file, `&lt;` reads input from file. 

What does `&lt;&lt;` exactly do?

And is there a man page for it?

How does &quot;cat &lt;&lt; EOF&quot; work in bash?

How could I merge / convert multiple PDF files into one large PDF file?

I tried the following, but the content of the target file was not as expected:

    convert file1.pdf file2.pdf merged.pdf

I need a very simple/basic command line (CLI) solution. Best would be if I could pipe the output of the merge / convert straight into `pdf2ps` ( as originally attempted in my previously asked question here: https://stackoverflow.com/questions/2507596/linux-piping-convert-pdf2ps-lp ).

Merge / convert multiple PDF files into one PDF

Why is it necessary though everything is specified in a makefile ?

What does a typical ./configure do in Linux?

What is the proper way to get a list of all available serial ports/devices on a Linux system?

In other words, when I iterate over all devices in `/dev/`, how do I tell which ones are serial ports in the classic way, that is, those usually supporting baud rates and [RTS/CTS][3] flow control?

The solution would be coded in C.

I ask because I am using a third-party library that does this clearly wrong: It appears to only iterate over `/dev/ttyS*`. The problem is that there are, for instance, serial ports over USB (provided by USB-RS232 adapters), and those are listed under /dev/ttyUSB*. And reading the [Serial-HOWTO at Linux.org][1], I get the idea that there&#39;ll be other name spaces as well, as time comes.

So I need to find the official way to detect serial devices. The problem is that none appears to be documented, or I can&#39;t find it.

I imagine one way would be to open all files from `/dev/tty*` and call a specific `ioctl()` on them that is only available on serial devices. Would that be a good solution, though?

### Update ###

*hrickards* suggested to look at the source for &quot;setserial&quot;.
Its code does exactly what I had in mind:

First, it opens a device with:

    fd = open (path, O_RDWR | O_NONBLOCK)

Then it invokes:

    ioctl (fd, TIOCGSERIAL, &amp;serinfo)

If that call returns no error, then it&#39;s a serial device, apparently.

I found similar code in *[Serial Programming/termios][2]*, which suggested to also add the `O_NOCTTY` option.

**There is one problem with this approach, though:**

When I tested this code on BSD Unix (that is, Mac&amp;nbsp;OS&amp;nbsp;X), it worked as well. ***However***, serial devices that are provided through Bluetooth cause the system (driver) to try to connect to the Bluetooth device, which takes a while before it&#39;ll return with a timeout error. This is caused by just opening the device. And I can imagine that similar things can happen on Linux as well - ideally, I should not need to open the device to figure out its type. I wonder if there&#39;s also a way to invoke `ioctl` functions without an open, or open a device in a way that it does not cause connections to be made?

What should I do?

  [1]: http://www.linux.org/docs/ldp/howto/Serial-HOWTO.html
  [2]: http://en.wikibooks.org/wiki/Serial_Programming:Unix/termios
  [3]: http://en.wikipedia.org/wiki/RS-232#RTS.2FCTS_handshaking


How to find all serial devices (ttyS, ttyUSB, ..) on Linux without opening them?

I have an ArrayList that I want to use to hold RaceCar objects that extend the Thread class as soon as they are finished executing. A class, called Race, handles this ArrayList using a callback method that the RaceCar object calls when it is finished executing. The callback method, addFinisher(RaceCar finisher), adds the RaceCar object to the ArrayList. This is supposed to give the order in which the Threads finish executing.

I know that ArrayList isn&#39;t synchronized and thus isn&#39;t thread-safe. I tried using the Collections.synchronizedCollection(c Collection) method by passing in a new ArrayList and assigning the returned Collection to an ArrayList. However, this gives me a compiler error:

    Race.java:41: incompatible types
    found   : java.util.Collection
    required: java.util.ArrayList
    finishingOrder = Collections.synchronizedCollection(new ArrayList(numberOfRaceCars));

Here is the relevant code:

    public class Race implements RaceListener {
        private Thread[] racers;
        private ArrayList finishingOrder;
        
        //Make an ArrayList to hold RaceCar objects to determine winners
        finishingOrder = Collections.synchronizedCollection(new ArrayList(numberOfRaceCars));
        		
        //Fill array with RaceCar objects
        for(int i=0; i&lt;numberOfRaceCars; i++) {
	    racers[i] = new RaceCar(laps, inputs[i]);
		
            //Add this as a RaceListener to each RaceCar
            ((RaceCar) racers[i]).addRaceListener(this);
        }

        //Implement the one method in the RaceListener interface
        public void addFinisher(RaceCar finisher) {
            finishingOrder.add(finisher);
        }

What I need to know is, am I using a correct approach and if not, what should I use to make my code thread-safe? Thanks for the help!

How do I make my ArrayList Thread-Safe? Another approach to problem in Java?

I have attempted to implement a producer/consumer pattern in c#.  I have a consumer thread that monitors a shared queue, and a producer thread that places items onto the shared queue.  The producer thread is subscribed to receive data...that is, it has an event handler, and just sits around and waits for an OnData event to fire (the data is being sent from a 3rd party api).  When it gets the data, it sticks it on the queue so the consumer can handle it. 

When the OnData event does fire in the producer, I had expected it to be handled by my producer thread.  But that doesn&#39;t seem to be what is happening.  The OnData event seems as if it&#39;s being handled on a new thread instead!  Is this how .net always works...events are handled on their own thread?  Can I control what thread will handle events when they&#39;re raised?  What if hundreds of events are raised near-simultaneously...would each have its own thread?


In .NET, what thread will Events be handled in?

Can anyone explain the difference between a fork and a thread?

What is the difference between fork and thread?

As demonstrated in [this answer](https://stackoverflow.com/questions/2478397/atomic-swap-in-gnu-c/2478520#2478520) I recently posted, I seem to be confused about the utility (or lack thereof) of `volatile` in multi-threaded programming contexts.

My understanding is this: any time a variable may be changed outside the flow of control of a piece of code accessing it, that variable should be declared to be `volatile`.  Signal handlers, I/O registers, and variables modified by another thread all constitute such situations.

So, if you have a global int `foo`, and `foo` is read by one thread and set atomically by another thread (probably using an appropriate machine instruction), the reading thread sees this situation in the same way it sees a variable tweaked by a signal handler or modified by an external hardware condition and thus `foo` should be declared `volatile` (or, for multithreaded situations, accessed with memory-fenced load, which is probably a better a solution).

How and where am I wrong?

Why is volatile not considered useful in multithreaded C or C++ programming?

This is a short question. At some point my thread understand that it should suicide. What is the best way to do it:

1. Thread.currentThread().interrupt();
2. return;

By the way, why in the first case we need to use `currentThread`? Is `Thread` does not refer to the current thread?

How a thread should close itself in Java?

I am learning bash.

I would like to do a simple script that, when not arguments given, shows some message. And when I give numers as argument,s depending on the value, it does one thing or another.

I would also like to know suggestions for the best online manuals for beginners in bash

Thanks

Bash, no-arguments warning, and case decisions

I&#39;m trying to get the contents of a directory using shell script.

My script is:

    for entry in `ls $search_dir`; do
        echo $entry
    done

where `$search_dir` is a relative path. However, `$search_dir` contains many files with whitespaces in their names. In that case, this script does not run as expected.

I know I could use `for entry in *`, but that would only work for my current directory.

I know I can change to that directory, use `for entry in *` then change back, but my particular situation prevents me from doing that.

I have two relative paths `$search_dir` and `$work_dir`, and I have to work on both simultaneously, reading them creating/deleting files in them etc.

So what do I do now?

PS: I use bash.

How to get the list of files in a directory in a shell script?

I have to put in a bash variable the first line of a file. I guess it is with the grep command, but it is any way to restrict the number of lines?

How to get the first line of a file in a bash script?

I have a command, for example: `echo &quot;word1 word2&quot;`. I want to put a pipe (`|`) and get &quot;word1&quot; from the command.

    echo &quot;word1 word2&quot; | ....

What should I put after the pipe?





How can I retrieve the first word of the output of a command in Bash?

I&#39;m looking a way to build conditional assignments in bash:

In Java it looks like this:

    int variable= (condition) ? 1 : 0;



How to build a conditional assignment in bash?

I&#39;m looking for something like createdb in PostgreSQL or any other solution that would allow me to create database with a help of a shell command. Any hints?

How to create a database from shell command?

I see this at the top of Python files:

1. For Python 2 files
    ```python
    #!/usr/bin/env python
    ```
1. For Python 3 files
    ```python
    #!/usr/bin/env python3
    ```

It seems to me like the files run the same without that line.

Why do people write #!/usr/bin/env python on the first line of a Python script?

When looping recursively through folders with files containing spaces the shell script I use is of this form, copied from the [internet][1]:

        while IFS= read -r -d $&#39;\0&#39; file; do
          dosomethingwith &quot;$file&quot;        # do something with each file
        done &lt; &lt;(find /bar -name *foo* -print0)

I think I understand the IFS bit, but I don&#39;t understand what the &#39;`&lt; &lt;(...)`&#39; characters mean. Obviously there&#39;s some sort of piping going on here.

It&#39;s very hard to Google &quot;&lt; &lt;&quot; or &quot;&lt;(&quot;, you see. I tried &quot;angle bracket parenthesis&quot; and &quot;less-than parenthesis&quot; but didn&#39;t find anything.



  [1]: http://mywiki.wooledge.org/BashFAQ/020

What does &quot;&lt; &lt;(command args)&quot; mean in the shell?

I have a ridiculous question due to a ridiculous problem. 

Normally if I want to get the contents of an environment variable in UNIX shell, I can do

    echo ${VAR}

Let&#39;s assume, due to my ridiculous situation, that this isn&#39;t possible. 

How do I get the contents of an environment variable to stdout, without someone who is looking at the command itself (not the output), see the value of the environment variable.

I can picture the solution being something like `echo env(NAME_OF_VAR)` although I can&#39;t seem to find it. The solution has to work in sh.

PS I can&#39;t write a script for this, it must be a built in unix command (i know, ridiculous problem)

Thanks (and sorry for the absurdity)


Content Type	Original Author	Original Content on Stackoverflow
Question	Kiran	View Question on Stackoverflow
Solution 1 - Linux	Martin	View Answer on Stackoverflow
Solution 2 - Linux	tnorgd	View Answer on Stackoverflow
Solution 3 - Linux	mouviciel	View Answer on Stackoverflow

Multithreading in Bash

Linux Problem Overview

Linux Solutions

Solution 1 - Linux

Solution 2 - Linux

Solution 3 - Linux

Use of exit() function

How do I pass values to the constructor on my wcf service?

Attributions