Use `-d` (&lt;a href=&quot;http://perldoc.perl.org/functions/-X.html&quot;&gt;full list of file tests&lt;/a&gt;)

    if (-d &quot;cgi-bin&quot;) {
        # directory called cgi-bin exists
    }
    elsif (-e &quot;cgi-bin&quot;) {
        # cgi-bin exists but is not a directory
    }
    else {
        # nothing called cgi-bin exists
    }

As a note, `-e` doesn&#39;t distinguish between files and directories.  To check if something exists and is a plain file, use `-f`.

    struct AccountInfo
    {
       String Username;
       String Password;
    }

now if I want to have a `Nullable` instance I should write:

    Nullable&lt;AccountInfo&gt; myAccount = null;

But I want make the `struct` `Nullable` by nature and it can be used like this (without use of `Nullable&lt;T&gt;`):

    AccountInfo myAccount = null;

How to make a &#39;struct&#39; Nullable by definition?

In a simple WPF, I have renamed MainWindow class to MyClass and I got this error in App.g.cs:

        public static void Main() {
            MyClass.App app = new MyClass.App();
            app.InitializeComponent();
            app.Run();
        }

How can I fix this can&#39;t find anything on the internet ?

wpf The type name &#39;App&#39; does not exist in the type ... occurs after renaming MainWindow

To see if a file exists before using it, we can use:

    if (-e &quot;filename.cgi&quot;)
    {
     #proceed with your code
    } 

But how to indentify a directory exists or not?

How to see if a directory exists or not in Perl?

To see if a file exists before using it, we can use:
<pre><code class="hljs language-less">if (-e "filename.cgi")
{
 #proceed with your code
} 
</code></pre>
But how to indentify a directory exists or not?

I have a simple Perl script to read a file line by line. Code is below. I want to display two lines and break the loop. But it doesn&#39;t work. Where is the bug?


    $file=&#39;SnPmaster.txt&#39;;
    open(INFO, $file) or die(&quot;Could not open  file.&quot;);
    
    $count = 0;	
    foreach $line (&lt;INFO&gt;)	{	
    	print $line;	
    	if ($++counter == 2){
    	  last;
    	}
    }
    close(INFO);

Perl read line by line

What is the meaning of @_ in Perl?

Is there a built-in function to trim leading and trailing whitespace such that `trim(&quot; hello world &quot;) eq &quot;hello world&quot;`?

Perl: function to trim string leading and trailing whitespace

How can I get the name of the script?

For example, I have a Perl script with the name `XXX.pl`. This file contains:

    $name = #some function that obtains the script&#39;s own name
    print $name;

Output:

    XXX.pl

I would like to liken this to the CWD function that obtains the scripts directory. I need a function that obtains the script&#39;s name as well.



How to get the name of Perl script that is running

    $text_to_search = &quot;example text with [foo] and more&quot;;
    $search_string = &quot;[foo]&quot;;

    if ($text_to_search =~ m/$search_string/)
        print &quot;wee&quot;;

Please observe the above code. For some reason I would like to find the text &quot;[foo]&quot; in the $text_to_search variable and print &quot;wee&quot; if I find it. To do this I would have to ensure that the [ and ] is substituted with \[ and \] to make Perl treat it as characters instead of operators.

How can I do this without having to first replace `[` and `]` with `\[` and `\]` using a `s///` expression?



How can I use a variable for a regex pattern without interpreting meta characters?

I often see files named &#39;blabla.exe:Zone.Identifier&#39; when monitoring I/O with Process Monitor.  
The files are seen on network-drives.

![alt text][1]

- What are `Zone.Identifier` files?
- What does the colon mean in the filename?
- Is the colon related the file&#39;s extended attributes?
- How do I prevent these files from being created when I copy code files from Windows Explorer to a WSL directory?


  [1]: http://i.stack.imgur.com/92l8S.png

What are `Zone.Identifier` files, and how do I prevent them from being created?

For reading, there is the useful abstraction `Source`. How can I write lines to a text file?


How to write to a file in Scala?

I would like to append a new line to an existing file without erasing the current information of that file. In short, here is the methodology that I am using the current time: 

    import java.io.BufferedWriter;
    import java.io.FileWriter;
    import java.io.Writer;

    Writer output;
    output = new BufferedWriter(new FileWriter(my_file_name));  //clears file every time
    output.append(&quot;New Line!&quot;);
    output.close();

The problem with the above lines is simply they are erasing all the contents of my existing file then adding the new line text. 

I want to append some text at the end of the contents of a file without erasing or replacing anything.

How to add a new line of text to an existing file in Java?

I want to change a couple of files at one time, __iff__ I can write to all of them. I&#39;m wondering if I somehow can combine the multiple open calls with the `with` statement:

    try:
      with open(&#39;a&#39;, &#39;w&#39;) as a and open(&#39;b&#39;, &#39;w&#39;) as b:
        do_something()
    except IOError as e:
      print &#39;Operation failed: %s&#39; % e.strerror

If that&#39;s not possible, what would an elegant solution to this problem look like?

How can I open multiple files using &quot;with open&quot; in Python?

How can we append text in a file via a one-line command without using io redirection?

Append text to file from command line without using io redirection

For example I had a folder called `Temp&#39; and I wanted to delete or flush all files from this folder using PHP. Could I do this?


Deleting all files from a folder using PHP?

I have a folder in `C:\Folder1`

I want to copy all the contents of `Folder1` to another location, `D:\Folder2`

How do I do this using a batch file?

copying all contents of folder to another folder using batch file?

This will be a ***really*** simple freebie for a bash guru:

**Question**

Using bash, how do you make a classpath out of all files in a directory?

---

**Details**

Given a directory:

    LIB=/path/to/project/dir/lib

that contains nothing but *.jar files such as:

    junit-4.8.1.jar
    jurt-3.2.1.jar
    log4j-1.2.16.jar
    mockito-all-1.8.5.jar

I need to create a colon-separated classpath variable in the form:

    CLASSPATH=/path/to/project/dir/lib/junit-4.8.1.jar:/path/to/project/dir/lib/jurt-3.2.1.jar:/path/to/project/dir/lib/log4j-1.2.16.jar:/path/to/project/dir/lib/mockito-all-1.8.5.jar

Some seudo-code that nearly expresses the logic I&#39;m looking for would be along the lines of:

    for( each file in directory ) {
       classpath = classpath + &quot;:&quot; + LIB + file.name
    }


What is a ***simple*** way to accomplish this via bash script?

Using bash, how do you make a classpath out of all files in a directory?

This may be a very easy question for someone - I am able to use `list.files()` to obtain a list of files in a given directory, but if I want to get a list of directories, how would I do this?  Is it somehow right in front of me as an option within `list.files()`?

Also, I&#39;m using Windows, so if the answer is to shell out to some Linux/unix command, that won&#39;t work for me.

.NET for example has a `Directory.GetFiles()` method, and a separate `Directory.GetDirectories()`
method, so I figured R would have an analogous pair. Thanks in advance.


How to obtain a list of directories within a directory, like list.files(), but instead &quot;list.dirs()&quot;

What I need to do if Search a folder say `C:\example`

I then need to go through each file and check to see if it matches a few start characters so if files start

    temp****.txt
    tempONE.txt
    tempTWO.txt

So if the file starts with temp and has an extension .txt I would like to then put that file name into a `File file = new File(&quot;C:/example/temp***.txt);` so I can then read in the file, the loop then needs to move onto the next file to check to see if it meets as above.



Content Type	Original Author	Original Content on Stackoverflow
Question	Nano HE	View Question on Stackoverflow
Solution 1 - Perl	Brad Mace	View Answer on Stackoverflow

How to see if a directory exists or not in Perl?

Perl Problem Overview

Perl Solutions

Solution 1 - Perl

wpf The type name 'App' does not exist in the type ... occurs after renaming MainWindow

How to make a 'struct' Nullable by definition?

Attributions