Tech Juice

How it works

There are various files that may be executed by the Bash shell when it is started. Usually they follow this logic:

• When bash is invoked as an interactive login shell:
  1. Bash first reads and executes commands from the file /etc/profile, if that file exists.
  2. After reading that file, it looks for ~/.bash_profile, ~/.bash_login, and ~/.profile, in that order, and reads and executes commands from the first one that exists and is readable. Usually there is a default ~/.profile file, and ~/.bash_profile and ~/.bash_login usually do not exist.
• When bash is invoked as an interactive non-login shell:
  1. Bash reads and executes commands from /etc/bash.bashrc and ~/.bashrc, if these files exist.
  2. The standard ~/.profile sources (runs) ~/.bashrc if it exists.

A login shell means a session where you directly log into a system, e.g. setting up a remote SSH session or logging in through a non-graphical text terminal. A non-login shell is then the type of shells you open after logging in: typically in a graphical session when you open a new terminal window.

The bottom line is that you should put customisations that should always be executed in ~/.bashrc!
Example

Example: After installing…

If you have a bunch of files with tabs, and you want to replace these tabs with the appropriate amount of spaces then you can use the expand command.

$ expand --tabs=4 stuff.php > stuff.php

With the –tabs switch the tab width is denoted, in spaces. So in this example each tab is replaced with four spaces.

In order to run this command on all PHP files in a directory, including its subdirectories, use this script:

#!/bin/sh
#
# Iteratively replaces tabs in .php files with 4 spaces.
#
 
find . -name "*.php" | while read line
do
  expand --tabs=4 $line > $line.new
  mv $line.new $line
done

Save it to a file and execute it in the directory you want to run the expands:

// Create the file in the current directory
$ touch expand.sh
 
// Use a text-editor like 'nano' to put the script code in the file.
$ nano expand.sh
 
// Make the script executable
$ chmod +x expand.sh
 
// Run the script
$ ./expand.sh

Introduction

Screen is a window manager for Linux. The power of Screen is described well in this article:

The same way tabbed browsing revolutionized the web experience, GNU Screen can do the same for your experience in the command line. GNU Screen allows you to manage several interactive shell instances within the same “window.” By using different keyboard shortcuts, you are able to shuffle through the shell instances, access any of them directly, create new ones, kill old ones, attach and detach existing ones.

Instead of opening up several terminal instances on your desktop or using those ugly GNOME/KDE-based tabs, Screen can do it better and simpler. Not only that, with GNU Screen, you can share sessions with others and detach/attach terminal sessions. It is a great tool for people who have to share working environments between work and home. By adding a status bar to your screen environment, you are able to name your shell instances on the fly or via a configuration file called .screenrc that can be created on the user’s home directory.

If you are a Linux user, chances are you have been using additional Putty windows if you needed simultaneous access to more than one secure…

When opening an SSH session from a Windows box to a Linux machine using PuTTY I noticed some strange characters. The text looked like this:

warning: format â%dâ expects type âintâ, but argument 2 has type âint *â

I was puzzled, because I had not had experienced this problem before when using PuTTY. Typing echo $LANG in the bash terminal prompt showed that it was using en_US.UTF-8 as the character set . The problem was caused by PuTTY expecting a different character set (One of the Windows ISO-8859 charsets).

To solve this problem, PuTTY must be configured to speak the same language: UTF8. Here’s how:

1. Open the PuTTY configure dialogue by clicking in the upper left corner of the window and selecting “Change Settings…” from the menu.
2. Go to “Translation” on the left side tree menu and select “UTF-8” from the pulldown menu to the right.
3. Apply the settings.

Now the correct output will show:

warning: format ‘%d’ expects type ‘int’, but argument 2 has type ‘int *’