command

20+ Unix/Linux find command examples

Linux/Unix FAQ: Can you share some find command examples?

Sure. The Unix/Linux find command is very powerful. It can search the entire filesystem to find files and directories according to the search criteria you specify. Besides using the find command to locate files, you can also execute other Linux commands (grep, mv, rm, etc.) on the files and directories you find, which makes find extremely powerful. 

By Alvin Alexander on April 22, 2013

How to use curl to get headers from a URL

Curl FAQ: How do I use curl to get the headers from a website URL?

Short answer: Use curl's -I option, like this:

$ curl -I URL

Here's a specific example, including a real URL and results:

By Alvin Alexander on January 24, 2013

Java exec - execute a system command pipeline in Java

In earlier articles I've described how to execute system commands from Java applications. A long time ago I wrote my first article on this topic (How to execute system commands from Java), and more recently I wrote an updated version of that article titled "Executing system commands from Java using the ProcessBuilder and Process classes".

By Alvin Alexander on October 17, 2012

MySQL restore - How to restore a MySQL database from a backup

MySQL database FAQ: How do I restore a MySQL backup? (Also written as, "How do I restore a MySQL database dump?")

By Alvin Alexander on January 9, 2012

Show unique list elements with the Linux sort -u command

If you're ever working on a Unix or Linux system, and have a list with duplicated items in it, and want a smaller list of only the unique items in the list, the sort command is your friend.

I just ran into a situation where I generated a list of fonts on a Mac OS X (Unix) system, and my list ended up with a bunch of duplicated names, like this:

By Alvin Alexander on January 8, 2012

How to show the CentOS Linux version

CentOS Linux FAQ: What commands can I use to show what version of CentOS Linux I'm using?

There are at least two different ways to show what version of CentOS Linux you're using. First, you can use the Linux cat command on the /etc/redhat-release file. Here's the command, and sample output:

# cat /etc/redhat-release

CentOS release 5.6 (Final)

You can also use the lsb_release command with the -a option. Here's that command, and its output:

By Alvin Alexander on December 4, 2011

Ruby command line arguments

Ruby FAQ: How do I read command line arguments in a Ruby script (Ruby command line args)?

To read command line args in a Ruby script, use the special Ruby array ARGV to get the information you need. Here are a few examples.

1) Getting the number of command line args

To get the number of command line arguments passed in to your Ruby script, check ARGV.length, like this:

By Alvin Alexander on November 19, 2011

Unix/Linux grep command examples

Linux grep commands FAQ: Can you share some Linux/Unix grep command examples?

Sure. The name grep means "general regular expression parser", but you can think of the grep command as a "search" command for Unix and Linux systems: it's used to search for text strings and more-complicated "regular expressions" within one or more files.

I think it's easiest to learn how to use the grep command by showing examples, so let's dive right in.

By Alvin Alexander on April 22, 2013

How to find multiple filenames with Linux find

Linux find command FAQ: How can I write one find command to find multiple filenames (or filename patterns)? For example, I want to find all the files beneath the current directory that end with the file extensions ".class" and ".sh".

You can use the Linux find command to find multiple filename patterns at one time, but for most of us the syntax isn't very common. In short, the solution is to use the find command's "or" option, with a little shell escape magic. Let's take a look at several examples.

By Alvin Alexander on March 25, 2013

Linux alias command examples

Unix and Linux aliases are a really nice way of customizing the command line to work the way you want it to work. With alias commands, you're essentially doing a little programming, and creating new Unix and Linux commands custom-tailored to the way you work. You can create aliases to use instead of existing commands, and you can also create aliases as Linux command pipelines.

By Alvin Alexander on August 31, 2011
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