Once you grasp that **`[`** is a ***command***, a whole lot becomes clearer!

**`[`** is another way to spell &quot;`test`&quot;.

    help [

However while they do *exactly* the same, `test` turns out to have a more detailed help page. Check

    help test


...for more information.

---

Furthermore note that I&#39;m using, by intention, `help test` and not `man test`. That&#39;s because `test` and `[` are shell builtin commands nowadays. Their feature set might differ from `/bin/test` and `/bin/[` from coreutils which are the commands described in the `man` pages.

  [1]: http://www.manpagez.com/man/1/test/

From [another question](https://stackoverflow.com/questions/1035396/bash-shell-script-syntax-error):

&gt; A bit of history: this is because &#39;[&#39; was historically not a shell-built-in but a separate executable that received the expresson as arguments and returned a result. If you didn&#39;t surround the &#39;[&#39; with space, the shell would be searching $PATH for a different filename (and not find it) . – [Andrew Medico](https://stackoverflow.com/users/19405/andrew-medico) Jun 24 &#39;09 at 1:13

`[` is a command and `$CHOICE` should be an argument, but by doing `[$CHOICE` (without any space between `[` and `$CHOICE`) you are trying to run a command named `[$CHOICE`. The syntax for command is:

    command arguments separated with space

`[` is a `test` command. So it requires space.

&lt;p&gt;It&#39;s worth noting that &lt;var&gt;[&lt;/var&gt; is also used in glob matching, which can get you into trouble.&lt;/p&gt;

    $ echo [12345]
    [12345]
    $ echo oops &gt;3
    $ echo [12345]
    3


In terms of performance, what are the gains (or just differences) between:

    $(&#39;.myEl&#39;).click();

and 

    $(&#39;.myEl&#39;).trigger(&#39;click&#39;);

Are there any at all?

jQuery advantages/differences in .trigger() vs .click()

I&#39;ve noticed that the `Model.where` method always returns an array even if there is only one result where as the `Model.find` method doesn&#39;t. Is there any reason for this? I thought `Model.where` was the preferred function since Rails 3.X. 

Should I be using `Model.find` when I expect a single result and `Model.where` when I expect more than one result?

Rails .where vs .find

I was trying to write a Bash script that uses an `if` statement.
 
    if[$CHOICE -eq 1];

The script was giving me errors until I gave a space before and after `[` and before `]` as shown below:

    if [ $CHOICE -eq 1 ];

My question here is, why is the space around the square brackets so important in Bash?

Why should there be spaces around &#39;[&#39; and &#39;]&#39; in Bash?

I was trying to write a Bash script that uses an <code>if</code> statement.
<pre><code class="hljs language-ini">if[$CHOICE -eq 1];
</code></pre>
The script was giving me errors until I gave a space before and after <code>[</code> and before <code>]</code> as shown below:
<pre><code class="hljs language-ini">if [ $CHOICE -eq 1 ];
</code></pre>
My question here is, why is the space around the square brackets so important in Bash?

Here is example file:

    somestuff...
    all: thing otherthing
    some other stuff

What I want to do is to add to the line that starts with `all:` like this:

    somestuff...
    all: thing otherthing anotherthing
    some other stuff


How to add to the end of lines containing a pattern with sed or awk?

I have a text file with the following format. The first line is the &quot;KEY&quot; and the second line is the &quot;VALUE&quot;. 

    KEY 4048:1736 string
    3
    KEY 0:1772 string
    1
    KEY 4192:1349 string
    1
    KEY 7329:2407 string
    2
    KEY 0:1774 string
    1

I need the value in the same line as of the key. So the output should look like this...

    KEY 4048:1736 string 3
    KEY 0:1772 string 1
    KEY 4192:1349 string 1
    KEY 7329:2407 string 2
    KEY 0:1774 string 1

It will be better if I could use some delimiter like `$` or `,`:

    KEY 4048:1736 string , 3

How do I merge two lines into one?




How to merge every two lines into one from the command line?

From a bash script how can I quickly find out whether a port `445` is open/listening on a server.

I have tried a couple of options, but I want something quick:  
1. `lsof -i :445`  (Takes seconds)  
2. `netstat -an |grep 445 |grep LISTEN` (Takes seconds)  
3. `telnet` (it doesn&#39;t return)  
4. `nmap`, `netcat` are not available on the server  

It will be nice to know of a way that doesn&#39;t enumerate first and greps after that.


Efficiently test if a port is open on Linux?

Within a bash script, what would be the simplest way to verify that a git URL points to a valid git repo and that the script has access to read from it?

Protocols that should be supported are `git@`, `https://`, and `git://`. Curl fails on the `git://` protocol.

    git@github.com:UserName/Example.git
    https://UserName@github.com/UserName/Example.git
    git://github.com/UserName/Example.git

Note: I&#39;m not asking to check to see if a URL is syntactically correct, I need to verify that a repo exists at the URL location entered from within a bash script.

How to check the validity of a  remote git repository URL?

    x=$(find . -name &quot;*.txt&quot;)
    echo $x

if I run the above piece of code in Bash shell, what I get is a string containing several file names separated by blank, not a list.

Of course, I can further separate them by blank to get a list, but I&#39;m sure there is a better way to do it.

So what is the best way to loop through the results of a `find` command?

How to loop through file names returned by find?

I think I ran into a bug in Window&#39;s batch scripting.

I cannot set variables that are in an expanded if statement.

Here is an isolated part of my script:

    @echo off

    set success=1
    set Version=12345
    set Target=Client
    set Type=456
    set dir=
    set zip=
    
    if &quot;%Version%&quot;==&quot;&quot; set success=0
    if &quot;%Type%&quot;==&quot;&quot; set success=0
    
    if 1==1 set test=42
    
    if %success%==1 (
    	set test2=57005
    	if &quot;%Target%&quot;==&quot;Client&quot; (
    		set dir=ModName v%Version%
    		set zip=ModName v%Version% %Type%.zip
    		echo Version: %Version%
    		echo    Type: %Type%
    		echo.
    		echo  Target: %Target%
    		echo     dir: %dir%
    		echo     zip: %zip%
    		echo.
    		echo    test: %test%
    		echo   test2: %test2%
    	)
    ) else (
    	echo Not successful.
    )

This is the output from a brand new instance of cmd:

    C:\Users\RandomClown\Desktop&gt;test.bat
    Version: 12345
       Type: 456
    
     Target: Client
        dir:
        zip:
    
       test: 42
      test2:

What you should notice is that the single line if statement correctly sets stuff.
The multiline if will perform anything that is NOT a set. I dont think I missed anything.
Also, the multiline if statement is correctly executing the right lines, as the `else ( echo Not successful. )` lines did not execute.

Why did the lines not execute?

Windows Batch Variables Won&#39;t Set

I have the following if statement:

    String newStr4 = strr.split(&quot;2012&quot;)[0];
    if (newStr4.startsWith(&quot;Mon&quot;)) {
        str4.add(newStr4);
    }

I want it to include `startsWith`  `Mon` `Tues` `Weds` `Thurs` `Friday` etc. Is there a simple way to this when using strings? I tried `||` but it didn&#39;t work.


How to check if a string starts with one of several prefixes?

I have two tables, one is for news and the other one is for comments and I want to get the count of the comments whose status has been set as approved.

    SELECT
        ccc_news . *, 
        count(if(ccc_news_comments.id = &#39;approved&#39;, ccc_news_comments.id, 0)) AS comments
    FROM
        ccc_news
        LEFT JOIN
            ccc_news_comments
        ON ccc_news_comments.news_id = ccc_news.news_id
    WHERE
        `ccc_news`.`category` = &#39;news_layer2&#39;
        AND `ccc_news`.`status` = &#39;Active&#39;
    GROUP BY
        ccc_news.news_id
    ORDER BY
        ccc_news.set_order ASC
    LIMIT 20 

But the problem with this query is that the minimum value that is fetched for the comments column is 1 whether there is any comment existent corresponding to that news or not.

Any help would be highly appreciable.

Count with IF condition in MySQL query

I understand how this construct works:

&lt;!-- language: lang-py --&gt;

    for i in range(10):
        print(i)

        if i == 9:
            print(&quot;Too big - I&#39;m giving up!&quot;)
            break
    else:
        print(&quot;Completed successfully&quot;)

But I don&#39;t understand why `else` is used as the keyword here, since it suggests the code in question only runs if the `for` block does not complete, which is the opposite of what it does! No matter how I think about it, my brain can&#39;t progress seamlessly from the `for` statement to the `else` block. To me, `continue` or `continuewith` would make more sense (and I&#39;m trying to train myself to read it as such).

I&#39;m wondering how Python coders read this construct in their head (or aloud, if you like). Perhaps I&#39;m missing something that would make such code blocks more easily decipherable?

Why does python use &#39;else&#39; after for and while loops?

I have read a lot of topics about code refactoring and avoiding of if else statements. Actually, I have a class where I am using a lot of if - else conditions.

More details: I am using the pull parser and on each line of my soap response, I will check if there is a tag I am interested on, if not, check another tag etc:

     if(eventType == XmlPullParser.START_TAG) {
        		soapResponse= xpp.getName().toString();
        		
        		if (soapResponse.equals(&quot;EditorialOffice&quot;)){  
        			eventType = xpp.next();
        			if (xpp.getText()!=null){
        			editorialOffice += xpp.getText();
        			}
        		}	
        		else if (soapResponse.equals(&quot;EditorialBoard&quot;)){  
        			eventType = xpp.next();
        			if (xpp.getText()!=null){
        			editorialBoard += xpp.getText();
        			}
        		}
        		else if (soapResponse.equals(&quot;AdvisoryBoard&quot;)){  
        			eventType = xpp.next();
        			if (xpp.getText()!=null){
        			advisoryBoard += xpp.getText();
        			}
        		}	
        	}
        	eventType = xpp.next();
         }

Now, I would like to use something else, instead of those if else conditions, but I don&#39;t know what.

Can you please give me an example?

How to avoid a lot of if else conditions

I&#39;ve just started learning Ruby and Ruby on Rails and came across validation code that uses ranges:

    validates_inclusion_of :age, :in =&gt; 21..99
    validates_exclusion_of :age, :in =&gt; 0...21, :message =&gt; &quot;Sorry, you must be over 21&quot;

At first I thought the difference was in the inclusion of endpoints, but in the API docs I looked into, it didn&#39;t seem to matter whether it was `..` or `...`: it always included the endpoints.

However, I did some testing in irb and it seemed to indicate that `..` includes both endpoints, while `...` only included the lower bound but not the upper one. Is this correct?

Difference between &#39;..&#39; (double-dot) and &#39;...&#39; (triple-dot) in range generation?

Need some SQL syntax help :-)

Both databases are on the same server

    db1 = DHE
    db2 = DHE_Import

    UPDATE DHE.dbo.tblAccounts 
    INNER JOIN DHE_Import.dbo.tblSalesRepsAccountsLink 
        ON DHE.dbo.tblAccounts.AccountCode = DHE_Import.tblSalesRepsAccountsLink.AccountCode 
    SET DHE.dbo.tblAccounts.ControllingSalesRep = DHE_Import.dbo.tblSalesRepsAccountsLink.SalesRepCode

I can do a query in Access with linked tables with similar syntax - BUT SQL doesn&#39;t like it.

I&#39;m sure it&#39;s a simple issue :-D

Thanks!

Update Query with INNER JOIN between tables in 2 different databases on 1 server

My question is as above. Sorry, it&#39;s probably a duplicate but I couldn&#39;t find an example with the `&lt;?&gt;` on the end.

Why would you not just use `Class` as the parameter?

What does Class&lt;?&gt; mean in Java?

The well-cited [RIP Hash rocket post][1] would seem to imply the Hash Rocket syntax (`:foo =&gt; &quot;bar&quot;`) is deprecated in favor of the new-to-Ruby JSON-style hash (`foo: &quot;bar&quot;`), but I can&#39;t find any definitive reference stating the Hash Rocket form is actually deprecated/unadvised as of Ruby 1.9.

  [1]: http://web.archive.org/web/20130909062027/http://peepcode.com/blog/2011/rip-ruby-hash-rocket-syntax

Is Hash Rocket deprecated?

What is the difference between these two class declarations?  I don&#39;t understand why @class is utilized here.  Thanks. 

    @class TestClass;
    
    @interface TestClass: UIView {
    	UIImage *image1;
    	UIImage *image2;
    }

and 

    @interface TestClass: UIView {
    	UIImage *image1;
    	UIImage *image2;
    }

Content Type	Original Author	Original Content on Stackoverflow
Question	Shash	View Question on Stackoverflow
Solution 1 - Bash	johnsyweb	View Answer on Stackoverflow
Solution 2 - Bash	Cameron	View Answer on Stackoverflow
Solution 3 - Bash	Jahid	View Answer on Stackoverflow
Solution 4 - Bash	Prince John Wesley	View Answer on Stackoverflow
Solution 5 - Bash	Daniel	View Answer on Stackoverflow

Why should there be spaces around '[' and ']' in Bash?

Bash Problem Overview

Bash Solutions

Solution 1 - Bash

Solution 2 - Bash

Solution 3 - Bash

Solution 4 - Bash

Solution 5 - Bash

Rails .where vs .find

jQuery advantages/differences in .trigger() vs .click()

Attributions