The bang bang (`!!`) command is a shortcut to **repeat the previous command you entered in your terminal**. This command is very useful when you forget that you need admin rights to make a certain action, and lets you repeat it with super-user rights just by typing

    sudo !!

instead of typing arrow-up, scrolling to the beginning of the line, adding `sudo ` and hitting enter (imagine scrolling through those *loooong* `apt-get` commands). So many seconds gained! *Yay!*

[![sudo bang bang][1]](http://blog.alestanis.com/2013/02/27/the-bang-bang-command/)

There are many other bang-commands such as `!x`, `!?x`, `!!:p` and `!!*`. This [blog post][2] lists them and explains what they are for.


  [1]: http://i.stack.imgur.com/qwsbJ.png
  [2]: http://web.archive.org/web/20130731111822/https://craig-russell.co.uk/2011/09/28/bang-bang-command-recall-in-linux.html

I am learning svg from its official documents, there is such line. I don&#39;t get it, if it already has a `width` and `height` attribute, what is the point to specify it again in `viewBox=&quot;0 0 1500 1000&quot;` ? 
It is says, &quot;One px unit is defined to be equal to one user unit. Thus, a length of &quot;5px&quot; is the same as a length of &quot;5&quot;&quot; in the official docs, thus this viewBox is a 1500px wide and 1000 height view, which exceeds 300px and 200px. So why does it define the width and height value in the first place?  
   

     &lt;svg width=&quot;300px&quot; height=&quot;200px&quot; version=&quot;1.1&quot;
             viewBox=&quot;0 0 1500 1000&quot; preserveAspectRatio=&quot;none&quot;
             xmlns=&quot;http://www.w3.org/2000/svg&quot;&gt;

How to use the &lt;svg&gt; viewBox attribute?

I&#39;m currently designing a windows 8 store app using XAML but I have a minor sizing issue. I have a ListView with a DataTemple.

The code for my ListView &amp; DataTemplate are below:

    &lt;ListView x:Name=&quot;listPageItems&quot;
              Grid.Row=&quot;1&quot;
              SelectionMode=&quot;Extended&quot;
              IsSwipeEnabled=&quot;False&quot;
              ItemsSource=&quot;{Binding Mode=OneWay, Source={StaticResource items}}&quot;
              ItemTemplate=&quot;{StaticResource NavigationItemTemplate}&quot;
              ScrollViewer.VerticalScrollBarVisibility=&quot;Visible&quot;&gt;

    &lt;/ListView&gt;

    &lt;DataTemplate x:Key=&quot;NavigationItemTemplate&quot;&gt;    
            &lt;Grid Height=&quot;75&quot;&gt;
                &lt;Grid.RowDefinitions&gt;
                    &lt;RowDefinition Height=&quot;1.6*&quot; /&gt;
                    &lt;RowDefinition Height=&quot;*&quot; /&gt;
                &lt;/Grid.RowDefinitions&gt;
                &lt;Rectangle Fill=&quot;White&quot; /&gt;
                &lt;Rectangle Fill=&quot;{StaticResource SSEGreenBrush}&quot;
                           Grid.Row=&quot;1&quot; /&gt;
                &lt;Border BorderThickness=&quot;2&quot;
                        BorderBrush=&quot;{StaticResource SSEGreenBrush}&quot;
                        Grid.RowSpan=&quot;2&quot; /&gt;
                &lt;TextBlock x:Name=&quot;textTitle&quot;
                           Text=&quot;{Binding ClientName}&quot;
                           Style=&quot;{StaticResource TitleTextStyle}&quot;
                           Foreground=&quot;{StaticResource SSEBlueBrush}&quot;
                           Margin=&quot;10,5,5,5&quot; /&gt;
                &lt;StackPanel Orientation=&quot;Horizontal&quot;
                            Grid.Row=&quot;1&quot;
                            HorizontalAlignment=&quot;Stretch&quot;&gt;
                    &lt;TextBlock Text=&quot;Last Edit :&quot;
                               Style=&quot;{StaticResource SubtitleTextStyle}&quot;
                               Foreground=&quot;{StaticResource SSEBlueBrush}&quot;
                               Margin=&quot;3,0,0,3&quot;
                               VerticalAlignment=&quot;Center&quot; /&gt;
                    &lt;TextBlock Text=&quot;SurveyDate&quot;
                               Style=&quot;{StaticResource SubtitleTextStyle}&quot;
                               Foreground=&quot;{StaticResource SSEBlueBrush}&quot;
                               Margin=&quot;3,0,0,3&quot;
                               VerticalAlignment=&quot;Center&quot; /&gt;
                &lt;/StackPanel&gt;
            &lt;/Grid&gt;
        &lt;/DataTemplate&gt;

The listview is within a grid column with a fixed width of 240. 

When the view is displayed the ListViewItems don&#39;t stretch to the width of the ListView. I&#39;ve tried setting numerous properties including the HorizontalContentAlignment but I can&#39;t seem to get the ListViewItem to stretch!

Can anybody help?

Thanks in advance.

I&#39;m using Visual studio 2012, C# 4.5 and developing a Windows store app.





ListViewItem won&#39;t stretch to the width of a ListView

What is the purpose of sudo bang bang (`sudo !!`) and when might one need to use it?

[![make me a sandwich, sudo bang bang][1]](http://justinsomnia.org/2006/09/sudo-bang-bang/)

  [1]: http://i.stack.imgur.com/JTMlx.png

What exactly is sudo bang bang?

<p>What is the purpose of sudo bang bang (<code>sudo !!</code>) and when might one need to use it?</p>
<p><a href="http://justinsomnia.org/2006/09/sudo-bang-bang/" target="_blank" rel="noopener noreferrer"><img src="http://i.stack.imgur.com/JTMlx.png" alt="make me a sandwich, sudo bang bang"></a></p>


I am trying to evaluate the disk usage of a number of Unix user accounts.
Simply, I am using the following command:

    du -cBM --max-depth=1 | sort -n

But I’ve seen many error message like below. How can I exclude all such “Permission denied” messages from display?

    du: `./james/.gnome2&#39;: Permission denied

**My request could be very similar to the following list, by replacing “find” to “du”.**

https://stackoverflow.com/q/762348

The following thread does not work. I guess I am using bash.

https://stackoverflow.com/q/5463884

Exclude all permission denied messages from &quot;du&quot;

I&#39;m trying to run NuGet on Linux (Ubuntu 12). I have Mono 3.0.6 (compiled from source).

&lt;!-- language-all: lang-none --&gt;

    $ mono --runtime=v4.0.30319 .nuget/NuGet.exe update -self
    Checking for updates from https://nuget.org/api/v2/.
    Error getting response stream (Write: The authentication or decryption has failed.): SendFailure

The error is due to some certificate (the nuget.org one most likely) not being trusted, I gather. This [blog post has more details](http://monomvc.wordpress.com/2012/03/06/nuget-on-mono/).

So I&#39;ve run:

    $ mozroots --import --sync
    $ certmgr -ssl https://go.microsoft.com
    $ certmgr -ssl https://nugetgallery.blob.core.windows.net
    $ certmgr -ssl https://nuget.org

... to no avail.

NuGet Version is 2.3.0.0 (although I started out with some older version that also did not work either).

How can I fix this error?


NuGet on Linux: Error getting response stream

I am attempting to bind a socket to a port below:  
    
	if( bind(socket_desc,(struct sockaddr *) &amp;server, sizeof(server)) &lt; 0)
	{
		perror(&quot;bind failed. Error&quot;);
		return 1;
	}
	puts(&quot;bind done&quot;);
	

But it gives:

    $ ./serve   
    Socket created    
    bind failed. Error: Address already in use

Why does this error occur?


Bind failed: Address already in use

I am able to list all the directories by

    find ./ -type d

I attempted to list the contents of each directory and count the number of files in each directory by using the following command

    find ./ -type d | xargs ls -l | wc -l

But this summed the total number of lines returned by

    find ./ -type d | xargs ls -l

Is there a way I can count the number of files in each directory?



How to count number of files in each directory?

Using `ps -ef | grep tomcat` I found a tomcat server that is running. I tried `kill -9 {id}` but it returns &quot;No such process.&quot; What am I doing wrong? 

Here&#39;s an example:

    Admins-MacBook-Pro:test-parent tom.maxwell$ ps -ef | grep tomcat
    2043706342 39707 39695   0  3:40PM ttys000    0:00.00 grep tomcat
    Admins-MacBook-Pro:test-parent tom.maxwell$ kill -9 39707
    -bash: kill: (39707) - No such process

How do I kill this tomcat process in Terminal?

I have a string that looks like this:

     GenFiltEff=7.092200e-01

Using bash, I would like to just get the number after the `=` character. Is there a way to do this?

Get string after character

To speed up some bash script execution, I would like to keep the result of a command in a variable using command substitution, but the command substitution replaces the `0x0A` newline character by a space. For example:

    a=`df -H`
or

    a=$( df -H )
When I want to process further `$a`, the newline characters are replaced by a space and all the lines are now on one line, which is much harder to grep:

    echo $a

What would be the easy tricks to avoid the newline character being removed by the command substitution?

How to avoid bash command substitution to remove the newline character?

I use this command to find files with a given pattern and then rename them to something else

    find . -name &#39;*-GHBAG-*&#39; -exec bash -c &#39;echo mv $0 ${0/GHBAG/stream-agg}&#39; {} \;

As I run this command, I see some outputs like this

    mv ./report-GHBAG-1B ./report-stream-agg-1B
    mv ./reoprt-GHBAG-0.5B ./report-stream-agg-0.5B


However at the end, when I run `ls`, I see the old file names.

find a pattern in files and rename them

Using the github webhooks, I would like to be able to pull any changes to a remote development server. At the moment, when in the appropriate directory, `git pull` gets any changes that need to be made. However, I can&#39;t figure out how to call that function from within Python. I have tried the following:

&lt;!-- language: lang-python --&gt;

    import subprocess
    process = subprocess.Popen(&quot;git pull&quot;, stdout=subprocess.PIPE)
    output = process.communicate()[0]

But this results in the following error

    Traceback (most recent call last):
      File &quot;&lt;stdin&gt;&quot;, line 1, in &lt;module&gt;
      File &quot;/usr/lib/python2.7/subprocess.py&quot;, line 679, in __init__
        errread, errwrite)
      File &quot;/usr/lib/python2.7/subprocess.py&quot;, line 1249, in _execute_child
        raise child_exception
    OSError: [Errno 2] No such file or directory

Is there a way that I can call this bash command from within Python?




How can I call &#39;git pull&#39; from within Python?

I recognize that &lt;kbd&gt;Up&lt;/kbd&gt;/&lt;kbd&gt;Down&lt;/kbd&gt; will give you the command history. But, how do you look at past output by scrolling up and down?

I have used &lt;kbd&gt;Shift&lt;/kbd&gt;+&lt;kbd&gt;Page Up&lt;/kbd&gt;/&lt;kbd&gt;Page Down&lt;/kbd&gt;, &lt;kbd&gt;Alt&lt;/kbd&gt;+&lt;kbd&gt;Shift&lt;/kbd&gt;+&lt;kbd&gt;Up&lt;/kbd&gt;/&lt;kbd&gt;Down&lt;/kbd&gt; and &lt;kbd&gt;Page Up&lt;/kbd&gt;/&lt;kbd&gt;Page Down&lt;/kbd&gt; but none of these seem to work.

It is a Redhat Linux box.

How do you scroll up/down on the console of a Linux VM

I&#39;m a postgres novice. 

I installed the postgres.app for mac. I was playing around with the psql commands and I accidentally dropped the postgres database. I don&#39;t know what was in it. 

I&#39;m currently working on a tutorial: http://www.rosslaird.com/blog/building-a-project-with-mezzanine/

And I&#39;m stuck at `sudo -u postgres psql postgres`

ERROR MESSAGE: `psql: FATAL:  role &quot;postgres&quot; does not exist`

$ which psql 
     
    /Applications/Postgres.app/Contents/MacOS/bin/psql


This is what prints out of `psql -l`

	                                List of databases
	    Name    |   Owner    | Encoding | Collate | Ctype |     Access privileges     
	------------+------------+----------+---------+-------+---------------------------
	 user       | user       | UTF8     | en_US   | en_US | 
	 template0  | user       | UTF8     | en_US   | en_US | =c/user                  +
	            |            |          |         |       | user      =CTc/user      
	 template1  | user       | UTF8     | en_US   | en_US | =c/user                  +
	            |            |          |         |       | user      =CTc/user      
	(3 rows)



So what are the steps I should take? Delete an everything related to psql and reinstall everything?

Thanks for the help guys!

psql: FATAL: role &quot;postgres&quot; does not exist

This is odd. I have defined the following prompt in `zsh`:

    local user_host=&#39;%{$terminfo[bold]$fg[green]%}%n @ %m%{$reset_color%}&#39;
    local current_dir=&#39;%{$terminfo[bold]$fg[blue]%} %~%{$reset_color%}&#39;
    local git_branch=&#39;$(git_prompt_info)%{$reset_color%}&#39;
    local return_code=&quot;%(?..%{$fg[red]%}%? ↵%{$reset_color%})&quot;

    PROMPT=&quot;╭─${user_host} %D{[%a, %b %d %I:%M:%S]} ${current_dir} ${git_branch}
    ╰─%B$%b &quot;
    RPS1=&quot;${return_code}&quot;

It works great on `gnome-terminal` as well as in an `ansi-term` terminal in Emacs (&lt;kbd&gt;M-x&lt;/kbd&gt; `ansi-term`) - see the example below:

![prompt example gnome-terminal/ansi-term][1]

However, it does not work well under `multi-term` in Emacs as you can see below:

![prompt example multi-term][2]

I thought `multi-term` would be capable of interpreting the same set of escape characters that a terminal like  `gnome-terminal` or `ansi-term` does. Why is it not interpreting the escape characters returned by `git-prompt_info` and others correctly?

I have also tried:

* &lt;kbd&gt;M-x&lt;/kbd&gt; `set-terminal-coding-system` and setting it to `utf-8-unix`
* `TERM=eterm-color` within the multi-term terminal, or before calling Emacs, etc.
* `TERM=` within the multi-term terminal, or before calling Emacs, etc.
* Removing any `export TERM` from my `.zshrc`

# Update (January 29, 2014):

The best solution so far seems to be to do the following:

`TERM=xterm-256color`

but causes another problem that I have reported here: [Passing escape sequences to shells within ansi-term in Emacs][3].

  [1]: http://i.stack.imgur.com/MXj5G.png
  [2]: http://i.stack.imgur.com/PVXke.png
  [3]: https://unix.stackexchange.com/questions/111541/passing-escape-sequences-to-zsh-embedded-shells-within-ansi-term-in-emacs

Emacs multi-term not displaying special characters correctly

Ok, I&#39;m a bit new to Macs and OSX, but I picked one up so that I can do some troubleshooting on my Java programs with one since the company I work for uses a combination of OSX and Windows machines.  The problem I&#39;m running into is, when I install Java 7 from Oracle&#39;s website, it updates the preferences menu and appears to execute .jar files correctly when double-clicking them, but the terminal window&#39;s version is still 1.6.0_43 and running the same .jar file from the terminal results in runtime errors due to the older version.

When I navigate to /Library/Java/JavaVirtualMachines/ I&#39;m presented with an empty folder.  From what I&#39;ve seen in other articles, this is where the Java 1.7.0&#39;s version folder should be.  Any idea what&#39;s going on?  How can I get the terminal to use the correct version of Java?

Edit: @DWilches comment on his original answer: 
(1) 

    total 64
    lrwxr-xr-x  1 root  wheel   10 Mar 17 21:38 1.4 -&gt; CurrentJDK
    lrwxr-xr-x  1 root  wheel   10 Mar 17 21:38 1.4.2 -&gt; CurrentJDK
    lrwxr-xr-x  1 root  wheel   10 Mar 17 21:38 1.5 -&gt; CurrentJDK
    lrwxr-xr-x  1 root  wheel   10 Mar 17 21:38 1.5.0 -&gt; CurrentJDK
    lrwxr-xr-x  1 root  wheel   10 Mar 17 21:38 1.6 -&gt; CurrentJDK
    lrwxr-xr-x  1 root  wheel   10 Mar 17 21:38 1.6.0 -&gt; CurrentJDK
    drwxr-xr-x  8 root  wheel  272 Mar 17 21:38 A
    lrwxr-xr-x  1 root  wheel    1 Mar 17 21:38 Current -&gt; A
    lrwxr-xr-x  1 root  wheel   59 Mar 17 21:38 CurrentJDK -&gt; /System/Library/Java/JavaVirtualMachines/1.6.0.jdk/Contents

(2)

    ls -ld /usr/bin/java
    lrwxr-xr-x  1 root  wheel  74 Mar 17 21:38 /usr/bin/java -&gt; /System/Library/Frameworks/JavaVM.framework/Versions/Current/Commands/java

Edit: sorry for the mistake with a new answer, gotten too used to sites that block edits of the original post after so long...

Mac OSX Java Terminal version incorrect

I have a file.sh with this, when run show : TERM environment variable not set.

    
    smbmount //172.16.44.9/APPS/Interfas/HERRAM/sc5 /mnt/siscont5 -o 
    iocharset=utf8,username=backup,password=backup2011,r
    
    if [ -f /mnt/siscont5/HER.TXT ]; then
    	echo &quot;No puedo actualizar ahora&quot;
    	umount /mnt/siscont5
    else 
    	if [ ! -f /home/emni/siscont5/S5.TXT ]; then
    		echo &quot;Puedo actualizar... &quot;
    		touch /home/emni/siscont5/HER.TXT
    		touch /mnt/siscont5/SC5.TXT
    		mv -f /home/emni/siscont5/CCORPOSD.DBF /mnt/siscont5
    		mv -f /home/emni/siscont5/CCTRASD.DBF /mnt/siscont5
    		rm /mnt/siscont5/SC5.TXT
    		rm /home/emni/siscont5/HER.TXT
    		echo &quot;La actualizacion ha sido realizada...&quot;
    	else
    		echo &quot;No puedo actualizar ahora: Interfaz exportando...&quot;
    	fi
    fi
    umount /mnt/siscont5
    echo &quot;/mnt/siscont5 desmontada...&quot;

TERM environment variable not set

I need to count the _number of occurrences of a char in a string_ using Bash.

In the following example, when the char is (for example) `t`, it _`echo`s_ the correct number of occurrences of `t` in `var`, but when the character is comma or semicolon, it prints out zero:

    var = &quot;text,text,text,text&quot; 
    num = `expr match $var [,]`
    echo &quot;$num&quot;

Count occurrences of a char in a string using Bash

In the following program, if I set the variable `$foo` to the value 1 inside the first `if` statement, it works in the sense that its value is remembered after the if statement. However, when I set the same variable to the value 2 inside an `if` which is inside a `while` statement, it&#39;s forgotten after the `while` loop. It&#39;s behaving like I&#39;m using some sort of copy of the variable `$foo` inside the `while` loop and I am modifying only that particular copy. Here&#39;s a complete test program:

    #!/bin/bash
    
    set -e
    set -u 
    foo=0
    bar=&quot;hello&quot;  
    if [[ &quot;$bar&quot; == &quot;hello&quot; ]]
    then
        foo=1
        echo &quot;Setting \$foo to 1: $foo&quot;
    fi

    echo &quot;Variable \$foo after if statement: $foo&quot;   
    lines=&quot;first line\nsecond line\nthird line&quot; 
    echo -e $lines | while read line
    do
        if [[ &quot;$line&quot; == &quot;second line&quot; ]]
        then
    	foo=2
    	echo &quot;Variable \$foo updated to $foo inside if inside while loop&quot;
        fi
        echo &quot;Value of \$foo in while loop body: $foo&quot;
    done
    
    echo &quot;Variable \$foo after while loop: $foo&quot;
    
    # Output:
    # $ ./testbash.sh
    # Setting $foo to 1: 1
    # Variable $foo after if statement: 1
    # Value of $foo in while loop body: 1
    # Variable $foo updated to 2 inside if inside while loop
    # Value of $foo in while loop body: 2
    # Value of $foo in while loop body: 2
    # Variable $foo after while loop: 1
    
    # bash --version
    # GNU bash, version 4.1.10(4)-release (i686-pc-cygwin)

A variable modified inside a while loop is not remembered

I&#39;m trying to find a way to run multiple commands in parallel in `sh` and wait for it completion.

I&#39;ve found that following doesn&#39;t work (`sh: 1: Syntax error: &quot;;&quot; unexpected`):

    sh -c &#39;(sleep 3 &amp;&amp; echo 1) &amp; ; (sleep 3 &amp;&amp; echo 2) &amp; ;  wait&#39;

But this syntax works as expected:

    sh -c &#39;(sleep 3 &amp;&amp; echo 1) &amp; ;; (sleep 3 &amp;&amp; echo 2) &amp; ;;  wait&#39;

But I don&#39;t understand what is the difference.

What is the meaning of `;;` and when it should be used?

Dash double semicolon (;;) syntax

I have some files in linux. For example 2 and i need shuffling the files in one file.

For example

    $cat file1
    line 1
    line 2
    line 3
    line 4
    line 5
    line 6
    line 7
    line 8

and 

    $cat file2
    linea one
    linea two
    linea three
    linea four
    linea five
    linea six
    linea seven
    linea eight

And later that i shuffling the two files i can obtain something like:

    linea eight
    line 4
    linea five
    line 1
    linea three
    line 8
    linea seven
    line 5
    linea two
    linea one
    line 2
    linea four
    line 7
    linea six
    line 1
    line 6

Content Type	Original Author	Original Content on Stackoverflow
Question	alestanis	View Question on Stackoverflow
Solution 1 - Linux	alestanis	View Answer on Stackoverflow

What exactly is sudo bang bang?

Linux Problem Overview

Linux Solutions

Solution 1 - Linux

ListViewItem won't stretch to the width of a ListView

How to use the <svg> viewBox attribute?

Attributions