You can do `now.time_since_epoch()` to get a duration representing the time since the epoch, with [the clock&#39;s resolution](https://stackoverflow.com/q/8386128). To convert to milliseconds use [`duration_cast`](http://en.cppreference.com/w/cpp/chrono/duration/duration_cast):

    auto duration = now.time_since_epoch();
    auto millis = std::chrono::duration_cast&lt;std::chrono::milliseconds&gt;(duration).count();

I want to define a bash alias named `kill3000` to automate the following task:

&lt;!-- language: lang-none --&gt;

    $ lsof -i:3000
    
    COMMAND   PID USER   FD   TYPE  DEVICE SIZE/OFF NODE NAME
    ruby    13402 zero    4u  IPv4 2847851      0t0  TCP *:3000 (LISTEN)
    
    $ kill -9 13402



shell script to kill the process listening on port 3000?

**Firstly, if you&#39;re not using 9.1+, please [refer to this question](https://stackoverflow.com/q/1564056/124486).**

How do I install an extension to PostgreSQL 9.1?

How do I import modules or install extensions in PostgreSQL 9.1+?

I&#39;ve got a small problem caused by insufficient documentation of C++11.

I&#39;d like to obtain a time since epoch in milliseconds, or nanoseconds or seconds and then I will have to &quot;cast&quot; this value to another resolution.
I can do it using gettimeofday() but it will be to easy, so I tried to achieve it using std::chrono.

I tried:

    std::chrono::time_point&lt;std::chrono::system_clock&gt; now = 
        std::chrono::system_clock::now();

But I have no idea what is a resolution of obtained in this way time_point, and I don&#39;t know how to get this time as a simple unsigned long long, and I haven&#39;t any conception how to cast it to another resolution.


C++ chrono system time in milliseconds, time operations

I've got a small problem caused by insufficient documentation of C++11.
I'd like to obtain a time since epoch in milliseconds, or nanoseconds or seconds and then I will have to "cast" this value to another resolution.
I can do it using gettimeofday() but it will be to easy, so I tried to achieve it using std::chrono.
I tried:
<pre><code class="hljs language-c">std::chrono::time_point&#x3C;std::chrono::system_clock> now = 
 std::chrono::system_clock::now();
</code></pre>
But I have no idea what is a resolution of obtained in this way time_point, and I don't know how to get this time as a simple unsigned long long, and I haven't any conception how to cast it to another resolution.

How can I check if a `std::thread` is still running (in a platform independent way)?
It lacks a `timed_join()` method and `joinable()` is not meant for that.

I thought of locking a mutex with a `std::lock_guard` in the thread and using the `try_lock()` method of the mutex to determine if it is still locked (the thread is running), but it seems unnecessarily complex to me.

Do you know a more elegant method?

**Update:** To be clear: I want to check if the thread cleanly exited or not. A &#39;hanging&#39; thread is considered running for this purpose.

How to check if a std::thread is still running?

If i have a string is there a built in function to sort the characters or would I have to write my own?

for example:

    string word = &quot;dabc&quot;;

I would want to change it so that:

    string sortedWord = &quot;abcd&quot;;

Maybe using char is a better option? How would I do this in C++?

Sorting Characters Of A C++ String

I&#39;m using a cross compiler. My code is:

    class WindowsTimer{
    public:
      WindowsTimer(){
        _frequency.QuadPart = 0ull;
      } 
    private:
      static LARGE_INTEGER _frequency;
    };

I get the following error:

&gt; undefined reference to `WindowsTimer::_frequency&#39;


I also tried to change it to

    LARGE_INTEGER _frequency.QuadPart = 0ull;
or

    static LARGE_INTEGER _frequency.QuadPart = 0ull;

but I&#39;m still getting errors.

anyone knows why?

Undefined reference to a static member

I&#39;m reading [http://gcc.gnu.org/onlinedocs/libstdc++/manual/shared_ptr.html](https://web.archive.org/web/20140318233637/http://gcc.gnu.org/onlinedocs/libstdc++/manual/shared_ptr.html) and some thread safety issues are still not clear for me:

 1. Standard guarantees that reference counting is handled thread safe and it&#39;s platform independent, right?
 2. Similar issue - standard guarantees that only one thread (holding last reference) will call delete on shared object, right?
 3. shared_ptr does not guarantee any thread safety for object stored in it?

EDIT:

Pseudo code:

    // Thread I
    shared_ptr&lt;A&gt; a (new A (1));
    
    // Thread II
    shared_ptr&lt;A&gt; b (a);
    
    // Thread III
    shared_ptr&lt;A&gt; c (a);
    
    // Thread IV
    shared_ptr&lt;A&gt; d (a);
    
    d.reset (new A (10));

Calling reset() in thread IV will delete previous instance of A class created in first thread and replace it with new instance? Moreover after calling reset() in IV thread other threads will see only newly created object?

std::shared_ptr thread safety explained

Eclipse 3.7.1
CDT 1.4.1
GCC 4.6.2

This is an example of a piece of C++11 code:

    auto text = std::unique_ptr&lt;char[]&gt;(new char[len]);

The Eclipse editor complains about:

    Function &#39;unique_ptr&#39; could not be resolved

The Makefile compilation works fine. How to make Eclipse stop complaining about these sort of errors?


How to enable C++11/C++0x support in Eclipse CDT?

I am having similar requirement as this: https://stackoverflow.com/questions/4834202/convert-hhmmss-to-seconds-only

but in javascript. I have seen many examples of converting seconds into different formats but not HH:MM:SS into seconds. Any help would be appreciated. 

Convert HH:MM:SS string to seconds only in javascript

I am trying to get the date of the previous month with python.
Here is what i&#39;ve tried:

    str( time.strftime(&#39;%Y&#39;) ) + str( int(time.strftime(&#39;%m&#39;))-1 )

However, this way is bad for 2 reasons: First it returns 20122 for the February of 2012 (instead of 201202) and secondly it will return 0 instead of 12 on January.

I have solved this trouble in bash with

    echo $(date -d&quot;3 month ago&quot; &quot;+%G%m%d&quot;)

I think that if bash has a built-in way for this purpose, then python, much more equipped, should provide something better than forcing writing one&#39;s own script to achieve this goal. Of course i could do something like:

    if int(time.strftime(&#39;%m&#39;)) == 1:
        return &#39;12&#39;
    else:
        if int(time.strftime(&#39;%m&#39;)) &lt; 10:
            return &#39;0&#39;+str(time.strftime(&#39;%m&#39;)-1)
        else:
            return str(time.strftime(&#39;%m&#39;) -1)

I have not tested this code and i don&#39;t want to use it anyway (unless I can&#39;t find any other way:/)

Thanks for your help!


python date of the previous month

I&#39;m wondering if there is a *standard* or &quot;normal&quot; means of interpreting time interval data end points with respect to inclusiveness/exclusiveness of the value defining the end point. Note however that I am asking what the standard (or most common) ***convention*** is (if there is one), not for a dissertation on your personal preference. If you really want to provide a dissertation, please attach it to a reference to someone&#39;s published standard or a standard text on the matter. Open standards (that I don&#39;t have to pay to read) are greatly preferred unless they are fundamentally flawed :).

Of course there are 4 possibilities for a time interval from A to B:

 1. (A, B) - Both ends are exclusive.
 2. [A, B] - Both ends are inclusive.
 3. [A, B) - Start is inclusive and end is exclusive
 4. (A, B] - Start is exclusive and end is inclusive

Each of these has different characteristics (as I see it, feel free to point out more)

The [A, B] convention would have the seemingly inconvenient property that B is contained withing the inteval [A, B] and also [B, C]. This is particularly inconvenient if B is meant to represent the midnight boundary and you are trying to determine which day it falls on for example. Also, this means the duration of the interval is slightly irritatig to calculate since [A, B] where A = B should have a length of 1 and therefore the duration of [A, B] is (B - A) **+ 1** 

Similarly the (A, B) convention would have the difficulty that B falls within neither (A,B) nor (B,C)... continuing the analogy with day boundaries, midnight would be part of neither day. This is also logically inconvenient because [A, B] where A = B is a non-sense interval with duration less than zero, **but reversing A and B does not make it a valid interval**.

So I think I want either [A, B), or (A, B] and I can&#39;t figure out how to decide between them. 

So if someone has a link to a standards document, reference to a standard text or similar  that clarify the convention that would be great. Alternately, if you can link a variety of standards documents and/or references that more or less completely fail to agree, then I can just pick one that seems to have sufficient authority to CMA and be done with it :). 

Finally, I will be working in Java, so I am particularly susceptible to answers that work well in Java.


Is there a standard for inclusive/exclusive ends of time intervals?

How would I extract the time from a series of `POSIXct` objects discarding the date part?

For instance, I have:

    times &lt;- structure(c(1331086009.50098, 1331091427.42461, 1331252565.99979, 
    1331252675.81601, 1331262597.72474, 1331262641.11786, 1331269557.4059, 
    1331278779.26727, 1331448476.96126, 1331452596.13806), class = c(&quot;POSIXct&quot;, 
    &quot;POSIXt&quot;))

which corresponds to these dates:

    &quot;2012-03-07 03:06:49 CET&quot; &quot;2012-03-07 04:37:07 CET&quot; 
    &quot;2012-03-09 01:22:45 CET&quot; &quot;2012-03-09 01:24:35 CET&quot; 
    &quot;2012-03-09 04:09:57 CET&quot; &quot;2012-03-09 04:10:41 CET&quot;
    &quot;2012-03-09 06:05:57 CET&quot; &quot;2012-03-09 08:39:39 CET&quot;
    &quot;2012-03-11 07:47:56 CET&quot; &quot;2012-03-11 08:56:36 CET&quot;

Now, I have some values for a parameter measured at those times:

    val &lt;- c(1.25343125e-05, 0.00022890575, 
             3.9269125e-05, 0.0002285681875, 
             4.26353125e-05, 5.982625e-05, 
             2.09575e-05, 0.0001516951251, 
             2.653125e-05, 0.0001021391875)

I would like to plot val vs time of the day, irrespectively of the specific day when val was measured.

Is there a specific function that would allow me to do that?

Extracting time from POSIXct

I want to find out the following:
given a date (`datetime` object), what is the corresponding day of the week?

For instance, Sunday is the first day, Monday: second day.. and so on

And then if the input is something like today&#39;s date.


## Example

    &gt;&gt;&gt; today = datetime.datetime(2017, 10, 20)
    &gt;&gt;&gt; today.get_weekday()  # what I look for

The output is maybe `6` (since it&#39;s Friday)

How do I get the day of week given a date?

What is the correct way to reuse a moved container?

    std::vector&lt;int&gt; container;
    container.push_back(1);
    auto container2 = std::move(container);
    
    // ver1: Do nothing
    //container2.clear(); // ver2: &quot;Reset&quot;
    container = std::vector&lt;int&gt;() // ver3: Reinitialize

    container.push_back(2);
    assert(container.size() == 1 &amp;&amp; container.front() == 2);

From what I&#39;ve read in the C++0x standard draft; ver3 seems to be the correct way, since an object after move is in a 

&gt; &quot;Unless otherwise specified, such moved-from objects shall be placed
&gt; in a valid but unspecified state.&quot;

I have never found any instance where it is &quot;otherwise specified&quot;.

Although I find ver3 a bit roundabout and would have much preferred ver1, though vec3 can allow some additional optimization, but on the other hand can easily lead to mistakes.

Is my assumption correct?

Reusing a moved container?

I&#39;d like to create a class where the client can store a lambda expression like `[]() -&gt; void {}` as a field of the class, but I can&#39;t figure out how to do so.  [One answer suggested using `decltype`](https://stackoverflow.com/a/5849247/34537), which I tried with no success.   Here is a [ideone source link](http://ideone.com/9fC2K). The below is the source and result:

    #include &lt;cstdio&gt;
    auto voidLambda = []()-&gt;void{};

    class MyClass {
    public:
         decltype(voidLambda) t;
         MyClass(decltype(voidLambda) t) { 
            this-&gt;t = t;
         }
    };
   
    int main() {
       MyClass([] {
          printf(&quot;hi&quot;);
       });
    }

Result:

    prog.cpp: In constructor &#39;MyClass::MyClass(&lt;lambda()&gt;)&#39;:
    prog.cpp:3:79: error: no matching function for call to &#39;&lt;lambda()&gt;::__lambda0()&#39;
    prog.cpp:2:20: note: candidates are: &lt;lambda()&gt;::&lt;lambda&gt;(const&lt;lambda()&gt;&amp;)
    prog.cpp:2:20: note:                 &lt;lambda()&gt;::&lt;lambda&gt;(&lt;lambda()&gt;&amp;&amp;)
    prog.cpp:3:88: error: no match for &#39;operator=&#39; in &#39;((MyClass*)this)-&gt;MyClass::t = t&#39;
    prog.cpp: In function &#39;int main()&#39;:
    prog.cpp:5:27: error: no matching function for call to &#39;MyClass::MyClass(main()::&lt;lambda()&gt;)&#39;
    prog.cpp:3:48: note: candidates are: MyClass::MyClass(&lt;lambda()&gt;)
    prog.cpp:3:14: note:                 MyClass::MyClass(const MyClass&amp;)

Does anyone know how to do this?

How can I store a lambda expression as a field of a class in C++11?

How to convert `std::chrono::time_point` to calendar datetime string with fractional seconds?

For example: 

    &quot;10-10-2012 12:38:40.123456&quot;

How to convert std::chrono::time_point to calendar datetime string with fractional seconds?

What is the difference between `std::system_clock` and `std::steady_clock`? (An example case that illustrate different results/behaviours would be great).

If my goal is to precisely measure execution time of functions (like a benchmark), what would be the best choice between `std::system_clock`, `std::steady_clock` and `std::high_resolution_clock`?

Difference between std::system_clock and std::steady_clock?

I was trying to compile [this example program][1] using GCC (tested versions 4.5.1, 4.6.3, 4.8.4):

    #include &lt;iostream&gt;
    #include &lt;iomanip&gt;
    #include &lt;ctime&gt;
    #include &lt;chrono&gt;
     
    using std::chrono::system_clock;
     
    int main()
    {
        system_clock::time_point now = system_clock::now();
        std::time_t now_c = system_clock::to_time_t(
                                now - std::chrono::hours(24));
        std::cout &lt;&lt; &quot;One day ago, the time was &quot;
                  &lt;&lt; std::put_time(std::localtime(&amp;now_c), &quot;%F %T&quot;) &lt;&lt; &#39;\n&#39;;
    }

[But it tells me:][2]

    prog.cpp: In function &#39;int main()&#39;:
    prog.cpp:14:18: error: &#39;put_time&#39; is not a member of &#39;std&#39;

---

I thought, probably it&#39;s not implemented yet. So I tried to check the implementation status for this function. I only found this page:

 * http://gcc.gnu.org/projects/cxx0x.html

but there I could not find any note on `put_time` or `chrono` or alike. Can anyone point me to a resource that provides information on the implementation status for this library?

  [1]: http://en.cppreference.com/w/cpp/chrono/time_point
  [2]: http://ideone.com/XR1eF4

std::put_time implementation status in GCC?

I&#39;m using time.h in C++ to measure the timing of a function. 

    clock_t t = clock();
    someFunction();
    printf(&quot;\nTime taken: %.4fs\n&quot;, (float)(clock() - t)/CLOCKS_PER_SEC);

however, I&#39;m always getting the time taken as 0.0000. clock() and t when printed separately, have the same value. I would like to know if there is way to measure the time precisely (maybe in the order of nanoseconds) in C++ . I&#39;m using VS2010.

precise time measurement

I&#39;m trying to use chrono library for timers and durations.

I want to be able to have a `Duration frameStart;` ( from app start )
and a `Duration frameDelta;` ( time between frames )

I need to be able to get the `frameDelta` duration as milliseconds and float seconds.

How do you do this with the new c++11 `&lt;chrono&gt;` libraries?  I&#39;ve been working on it and googling ( information is sparse ). The code is heavily templated and requires special casts and things, I can&#39;t figure out how to use this library correctly.

Content Type	Original Author	Original Content on Stackoverflow
Question	Dejwi	View Question on Stackoverflow
Solution 1 - C++	R. Martinho Fernandes	View Answer on Stackoverflow

C++ chrono system time in milliseconds, time operations

C++ Problem Overview

C++ Solutions

Solution 1 - C++

How do I import modules or install extensions in PostgreSQL 9.1+?

shell script to kill the process listening on port 3000?

Attributions