What about `-mmin`?

    find /var/www/html/audio -daystart -maxdepth 1 -mmin +59 -type f -name &quot;*.mp3&quot; \
        -exec rm -f {} \;

From man find:
&lt;pre&gt;
-mmin n
        File&#39;s data was last modified n minutes ago.
&lt;/pre&gt;

Also, **make sure to test this first!**

&lt;pre&gt;
... -exec echo rm -f &#39;{}&#39; \;
          ^^^^ Add the &#39;echo&#39; so you just see the commands that are going to get
               run instead of actual trying them first.
&lt;/pre&gt;

How can I:

 - right-align the text in the ID column
 - make each of the columns auto size according to the text length of the cell with the longest visible data? 

Here is the code:

    &lt;ListView Name=&quot;lstCustomers&quot; ItemsSource=&quot;{Binding Path=Collection}&quot;&gt;
        &lt;ListView.View&gt;
            &lt;GridView&gt;
                &lt;GridViewColumn Header=&quot;ID&quot; DisplayMemberBinding=&quot;{Binding Id}&quot; Width=&quot;40&quot;/&gt;
                &lt;GridViewColumn Header=&quot;First Name&quot; DisplayMemberBinding=&quot;{Binding FirstName}&quot; Width=&quot;100&quot; /&gt;
                &lt;GridViewColumn Header=&quot;Last Name&quot; DisplayMemberBinding=&quot;{Binding LastName}&quot;/&gt;
            &lt;/GridView&gt;
        &lt;/ListView.View&gt;
    &lt;/ListView&gt;


&lt;h2&gt;partial answer:&lt;/h2&gt;

Thanks Kjetil, the GridViewColumn.CellTemplate works well and the Auto Width works of course but when the ObservativeCollection &quot;Collection&quot; is updated with longer-than-column-width data, the column sizes do not update themselves so that is only a solution for the initial display of data:

    &lt;ListView Name=&quot;lstCustomers&quot; ItemsSource=&quot;{Binding Path=Collection}&quot;&gt;
        &lt;ListView.View&gt;
            &lt;GridView&gt;
                &lt;GridViewColumn Header=&quot;ID&quot; Width=&quot;Auto&quot;&gt;
                    &lt;GridViewColumn.CellTemplate&gt;
                        &lt;DataTemplate&gt;
                            &lt;TextBlock Text=&quot;{Binding Id}&quot; TextAlignment=&quot;Right&quot; Width=&quot;40&quot;/&gt;
                        &lt;/DataTemplate&gt;
                    &lt;/GridViewColumn.CellTemplate&gt;
                &lt;/GridViewColumn&gt;
                &lt;GridViewColumn Header=&quot;First Name&quot; DisplayMemberBinding=&quot;{Binding FirstName}&quot; Width=&quot;Auto&quot; /&gt;
                &lt;GridViewColumn Header=&quot;Last Name&quot; DisplayMemberBinding=&quot;{Binding LastName}&quot; Width=&quot;Auto&quot;/&gt;
            &lt;/GridView&gt;
        &lt;/ListView.View&gt;
    &lt;/ListView&gt;

How to autosize and right-align GridViewColumn data in WPF?

UPDATE: I recently learned from [this question][1] that in the entire discussion below, I (and I am sure others did too) was a bit confusing: What I keep calling a rainbow table, is in fact called a hash table. Rainbow tables are more complex creatures, and are actually a variant of Hellman Hash Chains. Though I believe the answer is still the same (since it doesn&#39;t come down to cryptanalysis), some of the discussion might be a bit skewed.  
The question: &quot;[What are rainbow tables and how are they used?][1]&quot;

----------

Typically, I always recommend using a cryptographically-strong random value as salt, to be used with hash functions (e.g. for passwords), such as to protect against Rainbow Table attacks.  

But is it actually cryptographically necessary for the salt to be random? Would any unique value (unique per user, e.g. userId) suffice in this regard? It would in fact prevent using a single Rainbow Table to crack all (or most) passwords in the system...  
But does lack of entropy really weaken the cryptographic strength of the hash functions?  

----------

Note, I am not asking about why to use salt, how to protect it (it doesn&#39;t need to be), using a single constant hash (don&#39;t), or what kind of hash function to use.  
Just whether salt needs entropy or not.

----------

Thanks all for the answers so far, but I&#39;d like to focus on the areas I&#39;m (a little) less familiar with. Mainly implications for cryptanalysis - I&#39;d appreciate most if anyone has some input from the crypto-mathematical PoV.  
Also, if there are additional vectors that hadn&#39;t been considered, that&#39;s great input too (see @Dave Sherohman point on multiple systems).  
Beyond that, if you have any theory, idea or best practice - please back this up either with proof, attack scenario, or empirical evidence. Or even valid considerations for acceptable trade-offs... I&#39;m familiar with Best Practice (capital B capital P) on the subject, I&#39;d like to prove what value this actually provides.

----------

EDIT: Some really good answers here, but I think as @Dave says, it comes down to Rainbow Tables for common user names... and possible less common names too. However, what if my usernames are globally unique? Not necessarily unique for my system, but per each user - e.g. email address.  
There would be no incentive to build a RT for a single user (as @Dave emphasized, the salt is not kept secret), and this would still prevent clustering. Only issue would be that I might have the same email and password on a different site - but salt wouldnt prevent that anyway.  
So, it comes back down to cryptanalysis - IS the entropy necessary, or not? (My current thinking is it&#39;s not necessary from a cryptanalysis point of view, but it is from other practical reasons.)

  [1]: https://security.stackexchange.com/q/379/33


Non-random salt for password hashes

I have this command that I run every 24 hours currently.

    find /var/www/html/audio -daystart -maxdepth 1 -mtime +1 -type f -name &quot;*.mp3&quot; -exec rm -f {} \;

I would like to run it every 1 hour and delete files that are older than 1 hour. Is this correct:

    find /var/www/html/audio -daystart -maxdepth 1 -mtime **+0.04** -type f -name &quot;*.mp3&quot; -exec rm -f {} \;

I am not sure of my use of the decimal number??

Thanks for any corrections.

EDIT
----

OR could I just use **-mmin 60**? Is this correct?

EDIT2
----

I tried your test, good thing you suggested it. I got an empty result. I want all files **OLDER** than 60mins to be deleted! How can I do this?? Does my command actually do this?

find -mtime files older than 1 hour

I have this command that I run every 24 hours currently.
<pre><code class="hljs language-bash">find /var/www/html/audio -daystart -maxdepth 1 -mtime +1 -type f -name "*.mp3" -exec rm -f {} \;
</code></pre>
I would like to run it every 1 hour and delete files that are older than 1 hour. Is this correct:
<pre><code class="hljs language-bash">find /var/www/html/audio -daystart -maxdepth 1 -mtime **+0.04** -type f -name "*.mp3" -exec rm -f {} \;
</code></pre>
I am not sure of my use of the decimal number??
Thanks for any corrections.
<h4 id="edit"><a aria-hidden="true" tabindex="-1" href="#edit"></a>EDIT</h4>
OR could I just use -mmin 60? Is this correct?
<h4 id="edit2"><a aria-hidden="true" tabindex="-1" href="#edit2"></a>EDIT2</h4>
I tried your test, good thing you suggested it. I got an empty result. I want all files OLDER than 60mins to be deleted! How can I do this?? Does my command actually do this?

Surely there must be a way to do this easily! 

I&#39;ve tried the Linux command-line apps such as `sha1sum` and `md5sum` but they seem only to be able to compute hashes of individual files and output a list of hash values, one for each file. 

I need to generate a single hash for the entire contents of a folder (not just the filenames).

I&#39;d like to do something like

    sha1sum /folder/of/stuff &gt; singlehashvalue

**Edit:** to clarify, my files are at multiple levels in a directory tree, they&#39;re not all sitting in the same root folder.

Linux: compute a single hash for a given folder &amp; contents?

I have a program whose `STDERR` output I want to inspect and run `grep` on etc.

So I could redirect it to `STDOUT` and use grep, but the problem is, I do *not* want the original `STDOUT` content.

So, this one won&#39;t do

    cmd 2&gt;&amp;1 | grep pattern

because it will mix the original STDOUT and STDERR.

And this one doesn&#39;t work since grep doesn&#39;t read the STDERR output:

    cmd 1&gt;/dev/null | grep pattern

But also, this one won&#39;t work:

    cmd 1&gt;/dev/null 2&gt;&amp;1 | grep pattern

because the output will be completely empty, since everything gets written to `/dev/null`.

But there must be a simple way to do it?

How can I redirect STDERR to STDOUT, but ignore the original STDOUT?

How do you tell &lt;kbd&gt;Ctrl&lt;/kbd&gt; + &lt;kbd&gt;R&lt;/kbd&gt; reverse-i-search to &quot;reset itself&quot; and start searching from the bottom of your history every time?

**Background:** When using reverse-i-search in Bash, I always get stuck once it is finished searching up through the history and it cannot find any more matches. Sometimes I hit &lt;kbd&gt;Esc&lt;/kbd&gt; and re-invoke &lt;kbd&gt;Ctrl&lt;/kbd&gt; + &lt;kbd&gt;R&lt;/kbd&gt; a second time, expecting it to start a fresh new search from the bottom of my history. However, the &quot;pointer&quot; still seems to be at the previous place it left off in my history.

The problem is, I usually do not want this behavior. If I hit &lt;kbd&gt;Esc&lt;/kbd&gt;, and then re-invoke &lt;kbd&gt;Ctrl&lt;/kbd&gt; + &lt;kbd&gt;R&lt;/kbd&gt;, I would like that to indicate it should restart from the bottom again and work its way back up.

I am using Cygwin on Windows, as none of the so-far mentioned solutions work.

&lt;hr/&gt;

&lt;sub&gt;This question was marked as a [potential duplicate question][1]. This question is not a duplicate for the following reasons:&lt;/sub&gt;

 * &lt;sub&gt;The alternate question does not deal with Cygwin.&lt;/sub&gt;
 * &lt;sub&gt;The alternate question does not deal with how to **reset** the search to its initial state (instead it deals with simply going backward in search as well as forward).&lt;/sub&gt;

  [1]: https://stackoverflow.com/questions/791765





Control-r reverse-i-search in Bash: how do you &quot;reset&quot; the search in Cygwin?

I want to check in linux bash  whether a file was created more than x time ago.

let&#39;s say the file is called text.txt and the time is 2 hours.

     if [ what? ]
     then
         echo &quot;old enough&quot;
     fi


how do I check in bash whether a file was created more than x time ago?

Press alt + numeric in bash and you get (arg [numeric]) what is that?

(This type of question is better suited for asking a human, instead of trying to &quot;guess&quot; for the correct terminology to search on the documentation via internet).

Press alt + numeric in bash and you get (arg [numeric]) what is that?

I&#39;m debating whether I should learn PowerShell, or just stick with [Cygwin][1]/Perl scripts/Unix shell scripts, etc.

The benefit of PowerShell would be that the scripts could be more easily used by teammates that don&#39;t have Cygwin; however, I don&#39;t know if I&#39;d really be writing that many general purpose scripts, or if people would even use them.

Unix scripting is so powerful, does PowerShell come close enough to warrant switching over?

Here are some of the specific things (or equivalents) I would be looking for in PowerShell:

 - [grep][2]
 - sort
 - uniq
 - Perl (how close does PowerShell come to Perl&#39;s capabilities?)
 - [AWK][3]
 - [sed][4]
 - file (the command that gives file information)
 - etc.

  [1]: http://en.wikipedia.org/wiki/Cygwin
  [2]: http://en.wikipedia.org/wiki/Grep
  [3]: http://en.wikipedia.org/wiki/AWK
  [4]: http://en.wikipedia.org/wiki/Sed


Is PowerShell ready to replace my Cygwin shell on Windows?

Is there an equivalent to OSX `open` command in cygwin. `open` opens a file with the default application for that type.

I want to do something like

    $ magic-command file.xls
    #excel opens as if file.xls would have been double-clicked

    $ magic-command file.txt
    #notepad opens as if file.txt would have been double-clicked

You get the idea?

Basically something like a &quot;cygwin-double-click&quot; command.

Open a file from Cygwin

I have a bunch of `tar` files in a directory and I want to extract all the files from them at once.  But this doesn&#39;t seem to do anything:

    $ tar xf *.tar

What&#39;s going on here?  How do I untar a bunch of files at once?

How can you untar more than one file at a time?

If I run these commands from a script:

    #my.sh
    PWD=bla
    sed &#39;s/xxx/&#39;$PWD&#39;/&#39;
    ...
    $ ./my.sh
    xxx
    bla

it is fine.

But, if I run:

    #my.sh
    sed &#39;s/xxx/&#39;$PWD&#39;/&#39;
    ...
    $ ./my.sh
    $ sed: -e expression #1, char 8: Unknown option to `s&#39; 

I read in tutorials that to substitute environment variables from shell you need to stop, and &#39;out quote&#39; the `$varname` part so that it is not substituted directly, which is what I did, and which works only if the variable is defined immediately before.

How can I get sed to recognize a `$var` as an environment variable as it is defined in the shell?

   







Environment variable substitution in sed

How do you compile and execute a .cs file from a command-prompt window?

Compiling/Executing a C# Source File in Command Prompt

I am running command-line Python scripts from the Windows taskbar by having a shortcut pointing to the Python interpreter with the actual script as a parameter.

After the script has been processed, the interpreter terminates and the output window is closed which makes it impossible to read script output.

What is the most straightforward way to keep the interpreter window open until any key is pressed?

In batch files, one can end the script with pause. The closest thing to this I found in python is `raw_input()` *which is sub-optimal* because it requires pressing the return key (instead of any key).


How to pause a script when it ends on Windows?

I&#39;d like to automatically kill a command after a certain amount of time.  I have in mind an interface like this:

    % constrain 300 ./foo args

Which would run &quot;./foo&quot; with &quot;args&quot; but automatically kill it if it&#39;s still running after 5 minutes.

It might be useful to generalize the idea to other constraints, such as autokilling a process if it uses too much memory.

Are there any existing tools that do that, or has anyone written such a thing?

ADDED: Jonathan&#39;s solution is precisely what I had in mind and it works like a charm on linux, but I can&#39;t get it to work on Mac OSX.  I got rid of the SIGRTMIN which lets it compile fine, but the signal just doesn&#39;t get sent to the child process.  Anyone know how to make this work on Mac?

[Added: Note that an update is available from Jonathan that works on Mac and elsewhere.]

Command line command to auto-kill a command after a certain amount of time

I need a command line tool to dump standard Windows DLL version info so I can process it by means of a bash script (Cygwin).

As a Java developer I am not very used to Microsoft development tools (though I have a little bit of experience with Microsoft Visual Embedded C++ 4.0 and Microsoft Visual Basic 6.0).

The appropriate tool seems to be [mt.exe][1], as [stated on SO][2]. However the only chance I have found to get this little application is to download a 1.29 GB ISO of the [Windows SDK for Windows Server 2008 and .NET Framework][3]. I can not believe this is the only way to do it.

I have also found a little application on the Internet called [PEView][4], but it displays too much (and useless in my case) information and it is not a command line application.

Standard [objdump][5] bundled inside Cygwin can also dump some information about the DLL files, but I can not see the option to dump DLL version. Note that MajorImageVersion, MinorImageVersion and other fields dumped by this tool (with -p option) are not related to own DLL version.

Any alternatives about what to do? Maybe I missed some important objdump option? Is mt.exe my only choice? If this is the case, is it possible to get it separately from Windows SDK?

  [1]: http://msdn.microsoft.com/en-us/library/aa375649.aspx
  [2]: https://stackoverflow.com/questions/420852/reading-an-applications-manifest-file
  [3]: http://www.microsoft.com/downloads/thankyou.aspx?familyId=f26b1aa4-741a-433a-9be5-fa919850bdbf&amp;displayLang=en
  [4]: http://www.magma.ca/~wjr/
  [5]: http://en.wikipedia.org/wiki/Objdump


Command line tool to dump Windows DLL version?

I&#39;m looking to add a `crontab` entry to execute a script every 30 minutes, on the hour and 30 minutes past the hour or something close. I have the following, but it doesn&#39;t seem to run on 0.

    */30 * * * *

What string do I need to use?

The cron is running on OSX.

How would I get a cron job to run every 30 minutes?

I want to be able to programatically add a new cron job, what is the best way to do this?

From [my research][1], it seems I could dump the current crontab and then append a new one, piping that back into crontab:

    (crontab -l ; echo &quot;0 * * * * wget -O - -q http://www.example.com/cron.php&quot;) | crontab -

Is there a better way?

  [1]: http://drupal.org/node/175106

How can I programmatically create a new cron job?

I have a python script that&#39;ll be checking a queue and performing an action on each item:

    # checkqueue.py
    while True:
      check_queue()
      do_something()

How do I write a bash script that will check if it&#39;s running, and if not, start it.  Roughly the following pseudo code (or maybe it should do something like `ps | grep`?):

    # keepalivescript.sh
    if processidfile exists:
      if processid is running:
         exit, all ok
    
    run checkqueue.py
    write processid to processidfile

I&#39;ll call that from a crontab:

    # crontab
    */5 * * * * /path/to/keepalivescript.sh


How do I write a bash script to restart a process if it dies?

Some cygwin commands are `.exe` files, so you can run them with the standard Windows Scheduler, but others don&#39;t have an `.exe` extension so can&#39;t be run from DOS (it seems like). 

For example I want `updatedb` to run nightly.

How do I make cron work?

How do you run a crontab in Cygwin on Windows?

Does crontab have an argument for creating cron jobs without using the editor (crontab -e). If so, What would be the code create a cronjob from a Bash script?

Content Type	Original Author	Original Content on Stackoverflow
Question	Abs	View Question on Stackoverflow
Solution 1 - Bash	Sean Bright	View Answer on Stackoverflow

find -mtime files older than 1 hour

Bash Problem Overview

EDIT

EDIT2

Bash Solutions

Solution 1 - Bash

Non-random salt for password hashes

How to autosize and right-align GridViewColumn data in WPF?

Attributions