If you have `imagemagick` installed, 

    convert source.jpg -colorspace Gray destination.jpg (true grayscale only)
    convert source.jpg -monochrome destination.jpg (true black and white)
    convert source.jpg -separate destination.jpg (separate into gray channels)

If you don&#39;t care about losing the original file: `mogrify -colorspace Gray file`.

use one of: `-monochrome` or `-colorspace gray` options for `imagemagick` (`convert`).

i just created the symlink `sudo ln -s /usr/local/mysql/lib/libmysqlclient.18.dylib /usr/lib/libmysqlclient.18.dylib` and am wondering how i get rid of it if I wanted to. How would i do this?

How do I remove a symlink?

I have an object from `ggplot2`, say `myPlot`, how can I identify the ranges for the x and y axes?

It doesn&#39;t seem to be a simple multiple of the data values&#39; range, because one can rescale plots, modify axes&#39; ranges, and so on.  `findFn` (from `sos`) and Google don&#39;t seem to be turning up relevant results, other than how to set the axes&#39; ranges.

How can I extract plot axes&#39; ranges for a ggplot2 object?

How can I use `sips`, `imagemagic`, or another tool to convert an image to black and white (grayscale) via the command line? 

How can I convert an image to grayscale via the command line?

<p>How can I use <code>sips</code>, <code>imagemagic</code>, or another tool to convert an image to black and white (grayscale) via the command line?</p>


What delete command can be run to remove only files in given directory 

 - NOT directories
 - NOT sub-directories
 - NOT files in these sub-directories. 


Some files don&#39;t have extensions so `rm *.*` wont work...

There are thousands of files in this folder.

Any advice?


Remove only files in directory on linux NOT directories

I want to split a text with comma `,` not space ` ` in `for foo in list`. Suppose I have a CSV file `CSV_File` with following text inside it:

    Hello,World,Questions,Answers,bash shell,script
    ...

I used following code to split it into several words:

    for word in $(cat CSV_File | sed -n 1&#39;p&#39; | tr &#39;,&#39; &#39;\n&#39;)
    do echo $word
    done

It prints:

    Hello
    World
    Questions
    Answers
    bash
    shell
    script


But I want it to split the text by commas not spaces:

    Hello
    World
    Questions
    Answers
    bash shell
    script

How can I achieve this in bash?

How to split a list by comma not space

&gt; **Possible Duplicate:**  
&gt; [What are the differences between Perl, Python, AWK and sed?](https://stackoverflow.com/questions/366980/what-are-the-differences-between-perl-python-awk-and-sed)  
&gt; [What is the difference between sed and awk?](https://stackoverflow.com/questions/1632113/what-is-the-difference-between-sed-and-awk)  

&lt;!-- End of automatically inserted text --&gt;

Maybe not a very specific question, but I am confused about the differences between `grep`, `awk` and `sed` in terms of their role in Unix/Linux system administration and text processing. 

What are the differences among grep, awk &amp; sed?

I would like to embed a long command like this in a bash script:

    mycommand \
        --server myserver \
        --filename extremely/long/file/name/that/i/would/like/to/be/able/to/break/up/if/possible \
        --otherflag \
        --anotherflag

with the long filename broken up.

I could do this:

    # Insufficiently pretty
    mycommand \
        --server myserver \
        --filename extremely/long/file/name/\
    that/i/would/like/to/be/able/to/break/\
    up/if/possible \
        --otherflag \
        --anotherflag \

but it breaks the flow. I would _like_ to be able to write this:

    # Doesn&#39;t work
    mycommand \
        --server myserver \
        --filename extremely/long/file/name/\
             that/i/would/like/to/be/able/to/break/\
             up/if/possible \
        --otherflag \
        --anotherflag

but that doesn&#39;t work because it breaks up the string literal.

Is there a way to tell bash to break a string literal but ignore any leading spaces?

How do I break up an extremely long string literal in bash?

Every time, my application crash a core dump file is not generated. I remember that few days ago, on another server it **was** generated. I&#39;m running the app using screen in bash like this:

    #!/bin/bash
    ulimit -c unlimited
    while true; do ./server; done

As you can see I&#39;m using `ulimit -c unlimited` which is important if I want to generate a core dump, but it still doesn&#39;t generate it, when I got an segmentation fault.
How can I make it work?

Core dump file is not generated

I have an RGB image. I want to convert it to numpy array. I did the following

    im = cv.LoadImage(&quot;abc.tiff&quot;)
    a = numpy.asarray(im)

It creates an array with no shape. I assume it is a iplimage object.

how to convert an RGB image to numpy array?

In Firefox only my video thumbnails are displaying mysterious 2-3 pixels of white space between the bottom of my image and its border (see below).

I&#39;ve tried everything I can think of in Firebug with no luck.

How can I remove this white space?

![Screenshot displaying white space below image][2]


  [1]: http://bit.ly/nV6E2w
  [2]: http://i.stack.imgur.com/HtUlH.png

Remove white space below image

In my MVC application, I am using following code to upload a file.

**MODEL**

     public HttpPostedFileBase File { get; set; }

**VIEW**

    @Html.TextBoxFor(m =&gt; m.File, new { type = &quot;file&quot; })


Everything working fine .. But I am trying to convert the result fiel to byte[] .How can i  do this

**CONTROLLER**

     public ActionResult ManagePhotos(ManagePhotos model)
        {
            if (ModelState.IsValid)
            {
                byte[] image = model.File; //Its not working .How can convert this to byte array
            }
         }

Convert HttpPostedFileBase to byte[]

I&#39;ve looked for days and can not find any good leads on how I can draw a bubble or where a draw 9 patch images is to use as a background. I am a terrible artist. Can anyone help?

The best sample I found is here on Stack Overflow, but it&#39;s written in Objective C.

https://stackoverflow.com/questions/4442126/how-to-draw-a-speech-bubble-on-an-iphone




Android drawable speech bubble

I need to see if a specific image exists on my cdn.

I&#39;ve tried the following and it doesn&#39;t work:

    if (file_exists(http://www.example.com/images/$filename)) {
        echo &quot;The file exists&quot;;
    } else {
        echo &quot;The file does not exist&quot;;
    }

Even if the image exists or doesn&#39;t exist, it always says &quot;The file exists&quot;. I&#39;m not sure why its not working...

PHP: How to check if image file exists?

I am compressing files using [WinZip][1] on the command line. Since we archive on a daily basis, I am trying to add date and time to these files so that a new one is auto generated every time.

I use the following to generate a file name. Copy paste it to your command line and you should see a filename with a Date and Time component.

    echo Archive_%date:~-4,4%%date:~-10,2%%date:~-7,2%_%time:~0,2%%time:~3,2%%time:~6,2%.zip

Output

    Archive_20111011_ 93609.zip

However, my issue is *AM* vs *PM*. The AM time stamp gives me time ` 9` (with a leading blank space) vs. `10` naturally taking up the two spaces. 

I guess my issue will extend to the first nine days, first 9 months, etc. as well.

How do I fix this so that leading zeroes are included instead of leading blank spaces so I get `Archive_20111011_093609.zip`?

  [1]: https://en.wikipedia.org/wiki/WinZip


Batch command date and time in file name

I need to delete all empty folders from my application folder using windows command prompt?

How can I create a bat file like that?

Please help me.


How to delete empty folders using windows command prompt?

I am trying to display the last commit within Git, but I need the date in a special format.

I know that the log pretty format `%ad` respects the `--date` format, but the only `--date` format I can find is &quot;short&quot;. I want to know the others, and whether I can create a custom one such as:

    git -n 1 --date=**YYMMDDHHmm** --pretty=format:&quot;Last committed item in this release was by %%an, %%aD, message: %%s(%%h)[%%d]&quot;




How to change Git log date formats

I installed mySQL on my Mac. Beside starting the SQL server with mySQL.prefPane tool installed in System Preferences, I want to know the instructions to start from command-line.
I do as follows:

After

&gt; su root

I start the mySQL server by command-line, but it produces an error as below:

&gt; **sh-3.2#** /usr/local/mysql/bin/mysqld
&gt; 
&gt; **111028 16:57:43** [Warning] Setting lower_case_table_names=2 because
&gt; file system for /usr/local/mysql-5.5.17-osx10.6-x86_64/data/ is case
&gt; insensitive
&gt; 
&gt; **111028 16:57:43** [ERROR] Fatal error: Please read &quot;Security&quot; section of
&gt; the manual to find out how to run mysqld as root!
&gt; 
&gt; **111028 16:57:43** [ERROR] Aborting
&gt; 
&gt; **111028 16:57:43** [Note] /usr/local/mysql/bin/mysqld: Shutdown complete




How to start MySQL server from command line on Mac OS Lion?

From inside a batch file, I would like to test whether I&#39;m running with Administrator/elevated privileges.

The username doesn&#39;t change when &quot;Run as Administrator&quot; is selected, so that doesn&#39;t work.

If there were a universally available command, which has no effect, but requires administrative privileges, then I could run that and check for an error code in order to test for privileges.  So far, I haven&#39;t found such a command.  The commands I have found seem to return a single, non-specific error code, which could indicate anything, and they&#39;re prone to failure for a variety of reasons.

I only care about Windows 7, though support of earlier operating systems would be nice.


Content Type	Original Author	Original Content on Stackoverflow
Question	cwd	View Question on Stackoverflow
Solution 1 - Linux	mark	View Answer on Stackoverflow
Solution 2 - Linux	imm	View Answer on Stackoverflow

How can I convert an image to grayscale via the command line?

Linux Problem Overview

Linux Solutions

Solution 1 - Linux

Solution 2 - Linux

How can I extract plot axes' ranges for a ggplot2 object?

How do I remove a symlink?

Attributions