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Convert PNG to GIF via Command Line

devnet — Fri, 06 Nov 2009 18:24:03 +0000

I installed a bare bones Arch Linux system today and took a screenshot. With no graphics utilities installed, I needed a way to convert a PNG to a GIF for a Simple Machines forum template thumbnail. I figured I’d use a command line utility to help me and ImageMagick is installed by default on most distributions. A quick read through the ImageMagick manpage and I found the convert command and thought I’d share it with everyone. Use convert in the following fashion: convert [input-options] input-file [output-options] output-file

convert SMFPress.png -channel Alpha -threshold 80% -resize 120x120 thumbnail.gif

This did a quick, same-size conversion with little loss for me to display the thumbnail online. For more information on the options I used and other options that I didn’t use, take a peek at the ImageMagick Online Help Page for convert.

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Convert PNG to GIF via Command Line originally appeared on Yet Another Linux Blog on November 6, 2009.

Adding Color to Bash List Command Part II

devnet — Tue, 08 Sep 2009 18:25:16 +0000

I previously blogged about how to add color to the ‘ls’ command utilizing an config file and alias. I then stumbled across a nugget of wisdom from a Foresight Linux user on the developers mailing list who gave a handy command that remedies some problems with missing color in a terminal.

On some distributions, the system-wide /etc/DIR_COLORS* files are removed or not present. This results in no colors being given inside of a terminal when looking for color directories and filenames. If you find yourself in this boat, try the following command to re-populate this setting:

devnet-> cd ~/
devnet-> dircolors -p >.dircolors

This should create a default profile for colors for your session if it hasn’t been done or was accidentally removed. For more information on the dircolors command try ‘man dircolors’. Please also note that dircolors command uses the environmental variable LS_COLORS to set your session.

For more information on LS_COLORS and how it pertains to the terminal/shell/cli/prompt, there are a few blog posts that do an excellent job explaining here, here and here.

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Adding Color to Bash List Command Part II originally appeared on Yet Another Linux Blog on September 8, 2009.

Adding Color to Bash List Command

devnet — Fri, 05 Jun 2009 21:00:06 +0000

One of the things I love is being able to enter into a directory via terminal, list the contents, and quickly see which ones are executable or not and which ones are directories or are not directories IN COLOR (not everyone is perfect right?). This is specifically handy as I move through working with Slackware based distributions like the one I’m using now, Zenwalk Linux 6 and the /etc/rc.d/ directory. Most of the Red Hat based distributions out there that I’ve used have this set automatically…so I’m used to it. When I opened up a terminal in Zenwalk I found no color. A quick investigation of ~/.bashrc showed me that there are aliases set to display color…instead of ls I’d just use the letter L; 2 l’s for another option, 3 for another. It’s interesting, but not normally how I do business. See bashrc below:

devnet[~]$ cat ~/.bashrc
alias lll="ls -al --color"
alias ll="ls -l --color"
alias l='ls --color'
alias search='find . -name'
alias aterm="aterm -fg white -tr"
alias version='cat /etc/zenwalk-version'
alias dh='df -h'
export PS1='\u[\W]\$ '
export PAGER="most"
devnet[~]$

I don’t use those aliases much…others of you might do the ‘ll’ or ‘lll’ but it’s just not part of my routine. So, I added in just after line 4 in the code above:

alias ls='ls --color'

You can do this a few different ways…with any command line editor like emacs, vi, or nano/pico. It’s really up to you. The easiest way for new users is to use a text editor:

devnet[~]$ mousepad ~/.bashrc

This will launch the mousepad text editor in XFCE. If you’re in Gnome, try gedit. If KDE, give kwrite a try. You should see something like the following window pop up for editing:

You should see in the picture above, I’ve added in the alias needed to make me comfortable. After that, File >> Save. You’re set! Except, you may notice that when you type the command ‘ls’ there are no colors. So what gives? Well, we haven’t loaded our ./bashrc since we changed it. You don’t have to logout and back in to get things to work though…you can do this right from the terminal:

devnet[~]$ exec bash

Now try giving the ‘ls’ command a try again and you should see that it is in color. I know a lot of the more advanced Linux guys out there are probably saying, “why’d he waste a post on this! It’s easy” and you’d be right for a majority of users out there…I hope that this post finds some new user out there that may be stuck for an answer on how to do this. One final note on this as well: You will have to do this as the root user and change /root/.bashrc in order for your root user to also have color. Thanks for reading!

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Adding Color to Bash List Command originally appeared on Yet Another Linux Blog on June 5, 2009.

Read & Display Single Line of a File

devnet — Tue, 18 Nov 2008 21:38:49 +0000

Sometimes when I’m troubleshooting a PHP error and a function is called in the debugger that gives me a line number of a file to look at, I want to know what that line says without opening up the file. Using the command line, you can accomplish this in the following way:

head -n 96 filename.php | tail -n 1

This allows you to quickly display the 96th line of filename.php. Hope this helps someone like it has me.

Convert PNG to GIF via Command Line I installed a bare bones Arch Linux system today and...

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Read & Display Single Line of a File originally appeared on Yet Another Linux Blog on November 18, 2008.

Print Readable Man Pages

devnet — Wed, 14 Nov 2007 14:49:40 +0000

Ever wonder how you can get a man page in into a format you can read and print? There’s many methods of doing it (copy and paste is one) but one the easiest I’ve found is:

man command | col -x -b  > command.txt

Where command is the Linux command man page you want to print/view. From there, open up command.txt in your favorite gui text editor (gedit, kate) and you have a readable format that could be printed quite easily for reference.

Convert PNG to GIF via Command Line I installed a bare bones Arch Linux system today and...
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Print Readable Man Pages originally appeared on Yet Another Linux Blog on November 14, 2007.

Dealing with Runaway Processes

devnet — Mon, 12 Mar 2007 20:24:48 +0000

Have you ever been using your Linux distro and suddenly found a program won’t close? It’s frustrating when an application hangs. In Windows, one could right click on the taskbar and choose “Task Manager” and kill the hanging process (which doesn’t always work BTW). In Linux, you can also kill these hanging processes.

First, if you’re using KDE press Control-Escape. This will give all processes in a handy window called the KDE System Guard. Clicking the column heading for “System %” so the arrow on it appears facing up will sort the processes from highest system percentage to lowest. Find the process that seems to be hogging up all the resources (or if you know the name of the process, highlight that) and then hit the kill button. Your process should end it’s routines and exit.

You can also check out which program is hogging up your virtual memory with its process which can also slow things up. Clicking on the column “VmSize” and sorting largest to smallest will allow you to see this and select which process to kill. I often elect to select only user processes using the drop down menu at the top right hand corner of the KDE System Guard. Doing this filters out all system files and shows any hanging applications that are initiated by the user (which is often what is hanging for me).

Don’t worry if you see the same process more than once (for example, Apache or php may have multiple entries if you run a webserver…this is normal). If you’re using Gnome, you’ll either have to use the console method I explain below or launch the Gnome System Manager to get things rolling. Since I don’t use Gnome, I won’t cover the Gnome System Manager here.

Another way you can do things…especially if all Xwindows (KDE, Gnome, Fluxbox, etc) have frozen or are sluggish is to drop to a console. You can do this by killing the Xserver or by dropping to a console. You can press Alt-F2 or Alt-F3 and get directly to a console. Login as root. Now let’s take a look and see what processes are hogging up resources. Kill the Xserver and drop to a console by hitting Control-Alt-Backspace. For our purposes, I’ll assume you’ve made it to the console now.

There’s a quick console way of finding exactly what is consuming the most of your PC as far as processes are concerned. Using the the ‘top’ command will display those processes that are beasts and allow you to take note of them. Look for the process taking up the most CPU% (which should appear at the ‘top’ of your ‘top’ output). Pay specific attention to the PID column of that high CPU% item and make a note of it. This is the process ID number and every program running on a Linux box is assigned one by the Kernel. We’ve found the one making problems for us and have recorded the PID so let’s slay it. Hit Control-C to stop the top command and then type:

kill PID

Where PID is the process ID number you made a note of before. You may not get confirmation that the task has been immediately killed so let’s see if it is still running. We may not get the information we need by using top again since it is mainly for finding the higher consuming processes aka runaways. Instead, let’s use the ps command.

ps aux | more

This command outputs all processes in a nice way…using the | and ‘more’ command allows you to paginate the output so that if there are a TON of processes, you can use the spacebar or arrow keys to page down (you can do that with any command too BTW). Now look for that PID that we just killed in the second column and see if it is there. You could also get creative and use:

 ps aux | grep PID

Where PID is once again the PID you killed. The grep command will search through the results and echo back to you any matching entries it finds. If you didn’t find anything and couldn’t match your PID to that of any displayed in your ps aux command, you just successfully killed that beastly process. As always, for more information, please see the man pages (e.g. man ps or man top).

Hopefully, this allows you to more efficiently manage your processes…runaway or normal. If I’ve printed an error, please let me know via the comments below or if there is a more efficient way of doing things let me know there as well…I’m always open to improvement.

UPDATE: Please checkout the comments section for a few more tips on killing processes!

UPDATE2: Reader Scott M writes in the comments below “You don’t have to use the PID. You can use the -f option. e.g. if there are multiple instance of SomeProgram, you can kill them all with one command:

pkill -9 -f SomeProgram” Thanks Scott!

Convert PNG to GIF via Command Line I installed a bare bones Arch Linux system today and...
Adding Color to Bash List Command Part II I previously blogged about how to add color to the...

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Dealing with Runaway Processes originally appeared on Yet Another Linux Blog on March 12, 2007.