How to temporary configure network interfaces with iproute2

The ip command is newer and better than the old ifconfig. It displays the IP address, the netmask, the broadcast, the MAC address and other information. The ip is better than ifconfig, for a number of reasons: it works for

How to administrate groups with the Unix / Linux gpasswd command

The gpasswd command is used to administer groups in Linux and Unix. It writes group information in /etc/group and /etc/gshadow. Because the gpasswd command works with some files located in /etc, it needs to be used with root priviledges. Any

Exporting variables in shell scripting

The export command is mostly used when setting up a new PATH. You need to export a variable, in order to use it globally. By default, a variable can be used only local, unless it is exported. $ x=/home/razvan $

Just another “Unix and Linux shells” article

Traditionally, the default shell in the Unix systems is dash, for both the users and the system scripts. On GNU / Linux distros, bash has always been the default shell. Some new GNU / Linux distros use dash  as the

Bash wildcards: the square brackets [ ] and the curly brackets { }

In the previous wildcard post, I taught you how to use the asterisk * and the question mark ? wildcards. This article is about other, not so popular wildcards: the square brackets [ ] and the curly brackets {}. Note:

The exit status in shell scripting

Like in the C programs, the exit command terminates a script. It can also return a value which is read by the script’s parent process. The exit status is also known as return status or exit code. By convention, a

What are the Zombie and the Orphan Processes and how to kill them?

What are the Zombie Processes? On Unix and Linux systems, the zombie (or defunct) processes are dead processes that still apear in the process table, usually because of bugs and coding errors. A zombie process remains in the operating system

Escaping characters in shell scripting

Escaping is a method of quoting single characters. The escape (\) preceding a character tells the shell to interpret that character literally. With some commands, like sed and echo, for example, the escaping has the opposite effect, it toggles on

Quoting characters in shell scripting

Quoting means putting a string in quotes. By quoting a string, we protect the special characters in the string from reinterpretation or expansion in a shell script. A special character is a character that has an different interpretation than its

How to send signals to processes in Linux and Unix

Killing a process doesn’t always mean stopping it. In this article I will show you how to send signals to processes with kill, pkill and killall and key combinations. How to kill processes by their PID: kill The kill command

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