According to [cplusplus.com][1]:

&gt; **failbit** is generally set by an input operation when the error was related to the internal logic of the operation itself, so other operations on the stream may be possible. While **badbit** is generally set when the error involves the loss of integrity of the stream, which is likely to persist even if a different operation is performed on the stream. badbit can be checked independently by calling member function bad.

In *simple words*, if you get a **number** when expect to retrieve a **letter**, it&#39;s `failbit`. If a **serious** error happens, which disrupts the ability to read from the stream at all - it&#39;s a `badbit`.

Except mentioned flags there is a third quite similar — `eofbit`. You can check the state using several functions: [`ios::fail`][2], [`ios::good`][3] and [`ios::bad`][4]

And you can get familiar with [**iostream library**][5] at MSDN resource too.

**Finally**, if you search for the **correct** solution of how to handling all error bits and exceptions while reading from the file (or accessing some file or directory), I highly recommend you read a very comprehensive and well-written article &quot;[Reading files in C++ using ifstream: dealing correctly with badbit, failbit, eofbit, and perror()][6]&quot;, at the end of which you will find a few **[Ideal solutions][7]**. The article is worth to read indeed.


  [1]: http://www.cplusplus.com
  [2]: http://www.cplusplus.com/reference/iostream/ios/fail/
  [3]: http://www.cplusplus.com/reference/iostream/ios/good/
  [4]: http://www.cplusplus.com/reference/iostream/ios/bad/
  [5]: http://msdn.microsoft.com/en-us/library/aa277347%28v=vs.60%29
  [6]: http://gehrcke.de/2011/06/reading-files-in-c-using-ifstream-dealing-correctly-with-badbit-failbit-eofbit-and-perror/
  [7]: http://gehrcke.de/2011/06/reading-files-in-c-using-ifstream-dealing-correctly-with-badbit-failbit-eofbit-and-perror/#ideal

I am looking for a way to open the method popup that shows up when you click the navigation-bar in XCode.

is there a way to do this by using a shortcut?


![enter image description here][1]


  [1]: http://i.stack.imgur.com/qZxtM.png

shortcut to open method dropdown in xcode

I&#39;m trying to learn C and I&#39;m currently trying to write a basic stack data structure, but I can&#39;t seem to get basic `malloc`/`free` right.

Here&#39;s the code I&#39;ve been using (I&#39;m just posting a small part here to illustrate a specific problem, not the total code, but the error message was generated just by running this example code in `valgrind`)

    #include &lt;stdio.h&gt;
    #include &lt;stdlib.h&gt;
    
    typedef struct Entry {
        struct Entry *previous;
        int value;
    } Entry;
    
    void destroyEntry(Entry entry);

    int main(int argc, char *argv[])
    {
        Entry* apple;
        apple = malloc(sizeof(Entry));
        destroyEntry(*(apple));
        return 0;
    }
    
    void destroyEntry(Entry entry)
    {
        Entry *entry_ptr = &amp;entry;
        free(entry_ptr);
        return;
    }

When I run it through `valgrind` with `--leak-check=full --track-origins=yes`, I get the following error:

&lt;!-- language: lang-none --&gt;

    ==20674== Invalid free() / delete / delete[] / realloc()
    ==20674==    at 0x4028E58: free (vg_replace_malloc.c:427)
    ==20674==    by 0x80485B2: destroyEntry (testing.c:53)
    ==20674==    by 0x8048477: main (testing.c:26)
    ==20674==  Address 0xbecc0070 is on thread 1&#39;s stack

I think this error means that the `destroyEntry` function is not allowed to modify memory allocated explicitly in main. Is that right? Why can&#39;t I just `free` the memory I allocated in `main` in another function? (and is this behavior somehow specific to main?)



Free memory allocated in a different function?

In case of `ifstream` in C++, under what conditions are `failbit` and `badbit` flags set ?

C++ ifstream failbit and badbit

<p>In case of <code>ifstream</code> in C++, under what conditions are <code>failbit</code> and <code>badbit</code> flags set ?</p>


I have seen a lot of people in the C++ community(particularly ##c++ on freenode) resent the use of `wstrings` and `wchar_t`, and their use in the windows api. What is exactly &quot;wrong&quot; with `wchar_t` and `wstring`, and if I want to support internationalization, what are some alternatives to wide characters?

What&#39;s &quot;wrong&quot; with C++ wchar_t and wstrings? What are some alternatives to wide characters?

Consider the following piece of code:

    #include &lt;stdio.h&gt;
    #include &lt;sys/types.h&gt;
    #include &lt;unistd.h&gt;

    int main(void)
    {
        int i;
        for(i = 0; i &lt; 2; i++)
        {
            fork();
            printf(&quot;.&quot;);
        }
        return 0;
    }


This program outputs 8 dots. How can that be possible? Should not there be 6 dots instead?

fork() branches more than expected?

Does someone know the way to define constant-sized vector?

For example, instead of defining

    std::vector&lt;int&gt;

it will be

    std::vector&lt;10, int&gt;

**It should be completely cross-platformed**. Maybe an open source class?

Constant-sized vector

I want to get the file names of all files that have a specific extension in a given folder (and recursively, its subfolders).  That is, the file name (and extension), not the full file path.  This is incredibly simple in languages like Python, but I&#39;m not familiar with the constructs for this in C++.   How can it be done?

How to get list of files with a specific extension in a given folder?

I&#39;m making a C++ wrapper for a piece of C code that returns a large array, and so I&#39;ve tried to return the data in a `vector&lt;unsigned char&gt;`.

Now the problem is, the data is on the order of **megabytes**, and `vector` unnecessarily *initializes* its storage, which essentially turns out to cut down my speed by half.

How do I prevent this?

Or, if it&#39;s not possible -- is there some other STL container that would avoid such needless work? Or must I end up making my own container?

(Pre-C++11)

### Note:

I&#39;m passing the vector *as my output buffer*. I&#39;m **not** copying the data from elsewhere.  
It&#39;s something like:

    vector&lt;unsigned char&gt; buf(size);   // Why initialize??
    GetMyDataFromC(&amp;buf[0], buf.size());

C++ vector that *doesn&#39;t* initialize its members?

I am using the following query to create a CSV file 

    SELECT email INTO OUTFILE &quot;mydata.csv&quot;
    FIELDS TERMINATED BY &#39;,&#39; OPTIONALLY ENCLOSED BY &#39;&quot;&#39;
    LINES TERMINATED BY &quot;\n&quot;
    FROM users;

But i am unable to find the mydata.csv file anywhere when i am searching through filezilla.

Any idea where this file is getting stored?

The query runs successfully without any errors! Any Help?



Can&#39;t find the file created by outfile in MySQL

I&#39;m trying to write huge amounts of data onto my SSD(solid state drive). And by huge amounts I mean 80GB.

I browsed the web for solutions, but the best I came up with was this:

    #include &lt;fstream&gt;
    const unsigned long long size = 64ULL*1024ULL*1024ULL;
    unsigned long long a[size];
    int main()
    {
        std::fstream myfile;
        myfile = std::fstream(&quot;file.binary&quot;, std::ios::out | std::ios::binary);
        //Here would be some error handling
        for(int i = 0; i &lt; 32; ++i){
            //Some calculations to fill a[]
            myfile.write((char*)&amp;a,size*sizeof(unsigned long long));
        }
        myfile.close();
    }

Compiled with Visual Studio 2010 and full optimizations and run under Windows7 this program maxes out around 20MB/s. What really bothers me is that Windows can copy files from an other SSD to this SSD at somewhere between 150MB/s and 200MB/s. So at least 7 times faster. That&#39;s why I think I should be able to go faster.

Any ideas how I can speed up my writing?

How to write a large buffer into a binary file in C++, fast?

I have a set of days of log files that I need to parse and look at in matlab. 

The log files look like this:

    LOG_20120509_120002_002.csv
    (year)(month)(day)_(hour)(minute)(second)_(log part number)

The logs increment hourly, but sometimes the seconds are one or two seconds off (per hour) which means i need to ignore what they say to do `loadcsv`.

I also have another file:

    LOG_DATA_20120509_120002.csv

which contains data for the whole hour (different data). 

The overall objective is to: 

     loop through each day 
         loop through each hour
             read in LOG_DATA for whole hour
             loop through each segment
                 read in LOG for each segment
                     compile a table of all the data

I guess the question is then, how do i ignore the minutes of the day if they are different? I suspect it will be by looping through all the files in the folder, in which case how do i do that?

Loop through files in a folder in matlab

I have a folder with ten files in it which I want to loop through. When I print out the name of the file my code works fine:

    import os
    indir = &#39;/home/des/test&#39;
    for root, dirs, filenames in os.walk(indir):
        for f in filenames:
            print(f)

Which prints:

    1
    2
    3
    4
    5
    6
    7
    8
    9
    10

But if I try to open the file in the loop I get an IO error:

    import os
    indir = &#39;/home/des/test&#39;
    for root, dirs, filenames in os.walk(indir):
        for f in filenames:
            log = open(f, &#39;r&#39;)

    Traceback (most recent call last):
    File &quot;/home/des/my_python_progs/loop_over_dir.py&quot;, line 6, in &lt;module&gt;
    log = open(f, &#39;r&#39;)
    IOError: [Errno 2] No such file or directory: &#39;1&#39;
    &gt;&gt;&gt; 

Do I need to pass the full path of the file even inside the loop to `open()` them?

Do I need to pass the full path of a file in another directory to open()?

I have a `data.table` that is not very big (2 GB) but for some reason `write.csv` takes an extremely long time to write it out (I&#39;ve never actually finished waiting) and seems to use a ton of RAM to do it.

I tried converting the `data.table` to a `data.frame` although this shouldn&#39;t really do anything since `data.table` extends `data.frame`. has anyone run into this?

More importantly, if you stop it with &lt;kbd&gt;Ctrl&lt;/kbd&gt;-&lt;kbd&gt;C&lt;/kbd&gt;, R does not seem to give memory back.


write.csv for large data.table

I am currently writing a program in c++ which includes reading lots of large text files. Each has ~400.000 lines with in extreme cases 4000 or more characters per line. Just for testing, I read one of the files using ifstream and the implementation offered by cplusplus.com. It took around 60 seconds, which is way too long. Now I was wondering, is there a straightforward way to improve reading speed?


edit:
The code I am using is more or less this: 

    string tmpString;
    ifstream txtFile(path);
    if(txtFile.is_open())
    {
    	while(txtFile.good())
    	{
    		m_numLines++;
    		getline(txtFile, tmpString);
    	}
    	txtFile.close();
    }

edit 2: The file I read is only 82 MB big. I mainly said that it could reach 4000 because I thought it might be necessary to know in order to do buffering.

edit 3: Thank you all for your answers, but it seems like there is not much room to improve given my problem. I have to use readline, since I want to count the number of lines. Instantiating the ifstream as binary didn&#39;t make reading any faster either. I will try to parallelize it as much as I can, that should work at least.

edit 4: So apparently there are some things I can to. Big thank you to sehe for putting so much time into this, I appreciate it a lot! =) 

Content Type	Original Author	Original Content on Stackoverflow
Question	Jake	View Question on Stackoverflow
Solution 1 - C++	Sergei Danielian	View Answer on Stackoverflow

C++ ifstream failbit and badbit

C++ Problem Overview

C++ Solutions

Solution 1 - C++

Free memory allocated in a different function?

shortcut to open method dropdown in xcode

Attributions