d126G

Delete, line number, go.

A lot of commands in Vim can be followed by a move command to specify the scope. 

    :.,126d

`.` is the actual line. If you want delete from the next line, you can use `.+1` instead.

In PHP, can I specify an interface to have fields, or are PHP interfaces limited to functions?

    &lt;?php
    interface IFoo
    {
        public $field;
        public function DoSomething();
        public function DoSomethingElse();
    }
    ?&gt;

If not, I realize I can expose a getter as a function in the interface:

    public GetField();

PHP: Can I Use Fields In Interfaces?

I&#39;ve recently read up quite a bit on IEEE 754 and the x87 architecture.  I was thinking of using NaN as a &quot;missing value&quot; in some numeric calculation code I&#39;m working on, and I was hoping that using *signaling* NaN would allow me to catch a floating point exception in the cases where I don&#39;t want to proceed with &quot;missing values.&quot;  Conversely, I would use *quiet* NaN to allow the &quot;missing value&quot; to propagate through a computation.  However, signaling NaNs don&#39;t work as I thought they would based on the (very limited) documentation that exists on them.

Here is a summary of what I know (all of this using x87 and VC++):

 - _EM_INVALID (the IEEE &quot;invalid&quot; exception) controls the behavior of the x87 when encountering NaNs
 -  If _EM_INVALID is masked (the exception is disabled), no exception is generated and operations can return quiet NaN.  An operation involving signaling NaN will **not** cause an exception to be thrown, but will be converted to quiet NaN.
 -  If _EM_INVALID is unmasked (exception enabled), an invalid operation (e.g., sqrt(-1)) causes an invalid exception to be thrown.
 -  The x87 **never** generates signaling NaN.
 -  If _EM_INVALID is unmasked, **any** use of a signaling NaN (even initializing a variable with it) causes an invalid exception to be thrown.

The Standard Library provides a way to access the NaN values:

    std::numeric_limits&lt;double&gt;::signaling_NaN();

and

    std::numeric_limits&lt;double&gt;::quiet_NaN();

The problem is that I see no use whatsoever for the signaling NaN.  If _EM_INVALID is masked it behaves exactly the same as quiet NaN.  Since no NaN is comparable to any other NaN, there is no logical difference.

If _EM_INVALID is *not* masked (exception is enabled), then one cannot even initialize a variable with a signaling NaN:
`double dVal = std::numeric_limits&lt;double&gt;::signaling_NaN();` because this throws an exception (the signaling NaN value is loaded into an x87 register to store it to the memory address).

You may think the following as I did:

 1. Mask _EM_INVALID.
 2. Initialize the variable with signaling NaN.
 3. Unmask_EM_INVALID.

However, step 2 causes the signaling NaN to be converted to a quiet NaN, so subsequent uses of it will **not** cause exceptions to be thrown!  So WTF?!

Is there any utility or purpose whatsoever to a signaling NaN?  I understand one of the original intents was to initialize memory with it so that use of an unitialized floating point value could be caught.

Can someone tell me if I am missing something here?


----------
**EDIT:**

To further illustrate what I had hoped to do, here is an example:

Consider performing mathematical operations on a vector of data (doubles).  For some operations, I want to allow the vector to contain a &quot;missing value&quot; (pretend this corresponds to a spreadsheet column, for example, in which some of the cells do not have a value, but their existence is significant).  For some operations, I do *not* want to allow the vector to contain a &quot;missing value.&quot;  Perhaps I want to take a different course of action if a &quot;missing value&quot; is present in the set -- perhaps performing a different operation (thus this is not an invalid state to be in).

This original code would look something like this:

    const double MISSING_VALUE = 1.3579246e123;
    using std::vector;

    vector&lt;double&gt; missingAllowed(1000000, MISSING_VALUE);
    vector&lt;double&gt; missingNotAllowed(1000000, MISSING_VALUE);

    // ... populate missingAllowed and missingNotAllowed with (user) data...

    for (vector&lt;double&gt;::iterator it = missingAllowed.begin(); it != missingAllowed.end(); ++it) {
        if (*it != MISSING_VALUE) *it = sqrt(*it); // sqrt() could be any operation
    }

    for (vector&lt;double&gt;::iterator it = missingNotAllowed.begin(); it != missingNotAllowed.end(); ++it) {
        if (*it != MISSING_VALUE) *it = sqrt(*it);
        else *it = 0;
    }

Note that the check for the &quot;missing value&quot; must be performed **every loop iteration**.  While I understand in most cases, the `sqrt` function (or any other mathematical operation) will likely overshadow this check, there are cases where the operation is minimal (perhaps just an addition) and the check is costly.  Not to mention the fact that the &quot;missing value&quot; takes a legal input value out of play and could cause bugs if a calculation legitimately arrives at that value (unlikely though it may be).  Also to be technically correct, the user input data should be checked against that value and an appropriate course of action should be taken.  I find this solution inelegant and less-than-optimal performance-wise.  This is performance-critical code, and we definitely do not have the luxury of parallel data structures or data element objects of some sort.

The NaN version would look like this:

    using std::vector;

    vector&lt;double&gt; missingAllowed(1000000, std::numeric_limits&lt;double&gt;::quiet_NaN());
    vector&lt;double&gt; missingNotAllowed(1000000, std::numeric_limits&lt;double&gt;::signaling_NaN());

    // ... populate missingAllowed and missingNotAllowed with (user) data...

    for (vector&lt;double&gt;::iterator it = missingAllowed.begin(); it != missingAllowed.end(); ++it) {
        *it = sqrt(*it); // if *it == QNaN then sqrt(*it) == QNaN
    }

    for (vector&lt;double&gt;::iterator it = missingNotAllowed.begin(); it != missingNotAllowed.end(); ++it) {
        try {
            *it = sqrt(*it);
        } catch (FPInvalidException&amp;) { // assuming _seh_translator set up
            *it = 0;
        }
    }

Now the explicit check is eliminated and performance should be improved.  I think this would all work if I could initialize the vector without touching the FPU registers...

Furthermore, I would imagine any self-respecting `sqrt` implementation checks for NaN and returns NaN immediately.

Usefulness of signaling NaN?

I know that to delete n lines, the command is [n]dd, where n is the number of lines to delete.

But what if I want to delete up to a certain line number? Say, if I&#39;m on line 65 and I want to delete up to line 126 without having to do the math, how could I do that?


Deleting up to a certain line in Vim

<p>I know that to delete n lines, the command is [n]dd, where n is the number of lines to delete.</p>
<p>But what if I want to delete up to a certain line number? Say, if I'm on line 65 and I want to delete up to line 126 without having to do the math, how could I do that?</p>


We are still in the design-phase of our project but we are thinking of having three separate processes on an embedded Linux kernel.   One of the processes with be a communications module which handles all communications to and from the device through various mediums.

The other two processes will need to be able to send/receive messages through the communication process.  I am trying to evaluate the IPC techniques that Linux provides; the message the other processes will be sending will vary in size, from debug logs to streaming media at ~5 Mbit rate.  Also, the media could be streaming in and out simultaneously.

Which IPC technique would you suggestion for this application?
http://en.wikipedia.org/wiki/Inter-process_communication

Processor is running around 400-500 Mhz if that changes anything.
Does not need to be cross-platform, Linux only is fine.
Implementation in C or C++ is required.


Which Linux IPC technique to use?

How can I get the [IPv4][1] address of an interface on Linux from C code?

For example, I&#39;d like to get the IP address (if any) assigned to eth0.

  [1]: http://en.wikipedia.org/wiki/IPv4


Get IP address of an interface on Linux

Every Modern OS provides today some atomic operations: 

- Windows has `Interlocked*` API
- FreeBSD has `&lt;machine/atomic.h&gt;`
- Solaris has `&lt;atomic.h&gt;`
- Mac OS X has `&lt;libkern/OSAtomic.h&gt;`

Anything like that for Linux?

- I need it to work on most Linux supported platforms including: x86, x86_64 and  **arm**.
- I need it to work on at least GCC and Intel Compiler.
- I need not to use 3rd par library like glib or qt.
- I need it to work in C++ (C not required)

Issues:

- GCC atomic builtins `__sync_*` are not supported on all platforms (ARM) and are not supported by the Intel compiler.
- AFAIK `&lt;asm/atomic.h&gt;` should not be used in user space and I haven&#39;t successfully used it at all. Also, I&#39;m not sure if it would work with Intel compiler.

**Any suggestions?**

I know that there are many related questions but some of them point to `__sync*` which is not feasible for me (ARM) and some point to `asm/atomic.h`.

Maybe there is an inline assembly library that does this for GCC (ICC supports gcc assembly)?

**Edit:** 

There is a very partial solution for add operations only (allows implementing atomic counter but not lock free-structures that require CAS):

If you use `libstc++` (Intel Compiler uses `libstdc++`) then you can use `__gnu_cxx::__exchange_and_add` that defined in `&lt;ext/atomicity.h&gt;` or `&lt;bits/atomicity.h&gt;`. Depends on compiler version.

However I&#39;d still like to see something that supports CAS.

How to perform atomic operations on Linux that work on x86, arm, GCC and icc?

I have a java app on linux which opens UDP socket and waits for messages.

After couple of hours under heavy load, there is a packet loss, i.e. the packets are received by kernel but not by my app (we see the lost packets in sniffer, we see UDP packets lost in netstat, we don&#39;t see those packets in our app logs).

We tried enlarging socket buffers but this didnt help - we started losing packets later then before, but that&#39;s it.

For debugging, I want to know how full the OS udp buffer is, at any given moment. Googled, but didn&#39;t find anything. Can you help me?

P.S. Guys, I&#39;m aware that UDP is unreliable. However - my computer receives all UDP messages, while my app is unable to consume some of them. I want to optimize my app to the max, that&#39;s the reason for the question. Thanks. 

How to monitor Linux UDP buffer available space?

I&#39;m running a PHP script via cron using Wget, with the following command:

    wget -O - -q -t 1 http://www.example.com/cron/run

The script will take a maximum of 5-6 minutes to do its processing. Will WGet wait for it and give it all the time it needs, or will it time out?

Does WGET timeout?

I need to clean up a file.  We have an xml parser that runs on it that is failing due to an escape character (0x1B) in the file.  How do I use vim to find where in the file that character is so I can remove it?



Example file:

    &lt;?php
    echo &quot;Hello, world.\n&quot;;                           
    ?&gt;

After conversion:

    0000000: 0a3c 3f70 6870 0a65 6368 6f20 2248 656c  .&lt;?php.echo &quot;Hel
    0000010: 6c6f 2c20 776f 726c 642e 5c6e 223b 0a3f  lo, world.\n&quot;;.?
    0000020: 3e0a  

  

So I delete a char: (in this example, the &#39;H&#39;)

    0000000: 0a3c 3f70 6870 0a65 6368 6f20 22 656c  .&lt;?php.echo &quot;Hel
    0000010: 6c6f 2c20 776f 726c 642e 5c6e 223b 0a3f  lo, world.\n&quot;;.?
    0000020: 3e0a

Notice how the first line isn&#39;t wide enough anymore.    When I convert it back, I get:

    ^@&lt;?php
    echo &quot;el^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@&gt; 



Use vim to search by hex code

I like that the long lines are displayed over more than one terminal line;  I don’t like that vim inserts newlines into my actual text. Which part of .vimrc I should change?

How to stop line breaking in vim

Instead of deleting the word and retyping all the letters once again in the opposite case, I&#39;d like to find some smart way in Vim to solve the problem.

How to change letters in a word from upper case to lower case or the other way around (swap case)?

I&#39;d like to search for an upper case word, for example COPYRIGHT in a file. I tried performing a search like:

    /copyright/i    # Doesn&#39;t work

but it doesn&#39;t work.  I know that in Perl, if I give the `i` flag into a regex it will turn the regex into a case-insensitive regex. It seems that Vim  has its own way to indicate a case-insensitive regex.

How to do case insensitive search in Vim

So when I want to create a new file by using the :e command I don&#39;t want to specify the whole path, just the new filename.  Can it be done?

How to set working/current directory in Vim?

I&#39;m looking for a way to make Vim have the ability to open a file by fuzzy-searching its name.

Basically, I want to be able to define a project once, and then have a shortcut which will give me a place to type a file name, and will match if any letters match up.

This kind of functionality exists in most editors I&#39;ve seen, but for the life of me I can&#39;t understand how to get Vim to do this.

Note that I&#39;m looking for something that **won&#39;t** require me to have any idea where in my directory tree a file is. I just want to be able to open it by the filename, regardless of what directory it&#39;s in.

Thanks

Opening files in Vim using Fuzzy Search

I am using FuzzyFinder with Vim to open files and switch between buffers. It works like a charm except when the current file I am working on has some changes. Vim wouldn&#39;t let me switch the buffer till I save it:

    &quot;E37: No write since last change (add ! to override)&quot;.

Is there a way of suppressing this warning unless I am quitting the editor? All I want to do it switch to a different buffer for referencing some code and switch back.

Unsaved buffer warning when switching files/buffers

I am using PuTTY and the vi editor. If I select five lines using my mouse and I want to delete those lines, how can I do that?

Also, how can I select the lines using my keyboard as I can in Windows where I press &lt;kbd&gt;Shift&lt;/kbd&gt; and move the arrows to select the text? How can I do that in vi?



How to delete selected text in the vi editor

As I&#39;m always dissatisfied with existing editors, a project I always wanted to start is my own text editor. However doing text editing is serious business.

Besides analyzing the source code of existing text editors, is there any book or other resource (like academic work) about this topic? I&#39;m interested especially in something that teaches how to handle memory and how to manage text insertion (if you have a 100 MB file and want to add a char at *x* position, you can&#39;t just `memmove` the huge text block...).

Content Type	Original Author	Original Content on Stackoverflow
Question	neuromancer	View Question on Stackoverflow
Solution 1 - Linux	Brian Rasmussen	View Answer on Stackoverflow
Solution 2 - Linux	sud03r	View Answer on Stackoverflow
Solution 3 - Linux	Zsolt Botykai	View Answer on Stackoverflow
Solution 4 - Linux	Peter	View Answer on Stackoverflow

Deleting up to a certain line in Vim

Linux Problem Overview

Linux Solutions

Solution 1 - Linux

Solution 2 - Linux

Solution 3 - Linux

Solution 4 - Linux

Usefulness of signaling NaN?

PHP: Can I Use Fields In Interfaces?

Attributions