Earlier, we looked at creating thousands of empty directories. Today, we’re going to get rid of them. But we need to get rid of only empty directories. To do so, we’ll use the find command: find . -depth -type d -empty -exec rmdir {} \; Now, we can put both into a script: mkdir $(printf '%05d\n' {1..10000}) find . -depth -type d -empty -exec rmdir {} \;
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Count Log Entries for a Pattern
You see a lot of entries for various things in log files. Here, we’re going to print out the number of entries with backupd in them: awk '/backupd/{print NR}' /var/log/system.log
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Bash: A Silly wc Example
The wc command is used to count words, characters and lines. Here, we’ll run it a few different ways. -l shows the number of lines in a file. For example, in my home directory, I can use it to see how many lines are in my .gitconfig file: wc -l .gitconfig This would output something like the following: 11 .gitconfig Or count the number of characters with -c: wc -c .gitconfig Or check the number of words: wc -w .gitconfig You can also run it against multiple files. For example, here I’ll check the number of lines in both my .gitconfig file and my .gitignore_global files: wc -l .gitconfig .gitignore_global…
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See Version Information In Linux
There are a number of ways to see information about what version of Linux that you’re running on different cat /etc/lsb-release Which returns the distribution information, parsed as follows: DISTRIB_ID=Ubuntu DISTRIB_RELEASE=12.04.5 DISTRIB_CODENAME=precise DISTRIB_DESCRIPTION="Ubuntu Precise Pangolin (LTS)" LSB_release can also be run as a command, as follows: lsb_release -a Which returns the following: No LSB modules are available. Distributor ID: Ubuntu Description: Ubuntu Precise Pangolin (LTS) Release: 12.04.5 Codename: precise lab_release can be used as a command as well: cat /etc/issue.net Which returns: Ubuntu Precise Pangolin (development branch) In Debian, you can simply look at the version file: cat /etc/debian_version Which returns the following: wheezy/sid Or Red Hat Enterprise can also…
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Linux Bash Commands
Popped in a list of Linux bash commands here: https://krypted.com//commands/linux-bash-commands/
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Fixing Color Problems with Ubuntu
The Terminal application defaults have a problem passing colors with Ubuntu and other types of Linux machines with properly formed .bashrc files. This is because those systems do not know how to interpret the Lion xterm-color256 terminal declaration. The fix is to change this setting to xterm-color. This needs to be done for each Terminal default. Click on each (Basic, Grass, Homebrew, etc) and then click on the Advanced tab. From there, just set the Declare terminal as: to xterm-color and close. This can also be done through the command line. These settings are stored in the com.apple.Terminal.plist per user, in their ~/Library/Preferences. The key for each is in TerminalType,…
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Using dirname and basename For Paths In Scripts
There are two commands that can be really helpful when scripting operations that involve filenames and paths. The first of these is dirname: dirname can be used to return the directory portion of a path. The second is basename: basename can be used to output the file name portion of a path. For our first example, let’s say that we have an output of /var/db/shadow/hash/850F62CD-966C-43A7-9C66-9F9E6799A955, which we know contains the encrypted password for a given user. To just see the UUID here would be done using the following extremely basic incantation of basename: basename /var/db/shadow/hash/850F62CD-966C-43A7-9C66-9F9E6799A955 Basename can also be used to trim output. For example, let’s say we didn’t need…
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Link Aggregation in Ubuntu 10
Ifenslave is an open source package that can be used to bond interfaces in Ubuntu 10. To install ifenslave, we can use apt-get: apt-get install ifenslave Once installed, we will need to take down our existing eth interfaces. Presumably these are eth0 and eth1, but you can use ifconfig to verify: ifconfig eth0 ifconfig eth1 Once you’ve verified the interfaces you want to bond, bring them down: ifdown eth0 ifdown eth1 Next, locate the entries in /etc/network/interfaces and comment out the corresponding lines: vi /etc/network/interfaces You will then need to add information for the link aggregated bond. Bond levels in ifenslave include: bond0: Round Robin with all interfaces active (likely…
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Programmatically Interacting with Google Apps
There are a number of ways that you can interact with Google Apps: there is the website, the new Google Cloud Connect and an API that allows you to integrate Google Apps with your own solutions. The API is available for python and java and can take some time to get used to, even though Google has done a good job with making it pretty straight forward (comparably). Therefore, there are a couple of tools that ease the learning curve a bit. GoogleCL on Ubuntu The first, and easiest is GoogleCL. GoogleCL is a command line version of Google Apps that will allow you to interact with YouTube, Picasa, Blogger…
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Ubuntu and Firewalling
Using the firewall in Ubuntu can be as easy or as hard as you want to make it. BSD variants all basically use the ipfw command whereas most of the rest of the *nix world will use netfilter. Netfilter has a number of front ends; the one that comes pre-installed in Ubuntu is ufw, short for ‘uncomplicated firewall’. Ufw is good for basic port management: allow and deny type of stuff. It’s not going to have the divert or throttling options. So let’s look at some basic incantations of ufw (you need to have elevated privileges to do all of this btw). Initial Configuration First you need to enable ufw,…