Bash Scripting – For Loop Explained With Examples

Loops are useful for automating repetitive tasks in Bash shell scripting. In this guide, we will learn about the for loop with examples.
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Bash Scripting – Functions Explained With Examples

In Bash scripting, functions are ways to group the set of instructions together to get a specific outcome. This guide explains how to use functions in bash scripts in Linux with examples.
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Bash Heredoc Tutorial For Beginners

When working with Bash scripts, you may end up in a situation where you have to process a series of inputs using the same command. Fortunately, there is a way in Bash to achieve this in a more optimal way using HereDoc. HereDoc, an acronym for Here Document, is an input redirection method to pass multiple […]

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Bash Redirection Explained With Examples

Redirection and piping are two useful features in bash scripting that sysadmins and developers use often. This guide explains what Bash Redirection is and how to work with Redirection in Bash with example commands.
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Edit sshd_config Using a Bash Script

Using Bash scripts can ensure consistent configuration of SSH and other services. Bash is the default shell on most Linux systems these days. It can be used as an interactive command-line interpreter as well as a scripting language to automate common tasks. This article shows you how to use a Bash script to ensure specific […]

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Bash Script to Monitor Memory Usage on Linux

This shell script will trigger an email when more than 60% of your system memory is used.
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Linux for Starters: Your Guide to Linux – Get Started with the Terminal – Part 9

There are many reasons why it’s useful to use bash and the command line. For example, command-line skills help with building repeatable data processes, the command-line makes working with text files easier, it uses fewer resources, can improve productivity and workflow, it’s great for scripting, and command-line skills are useful for cloud services. This is […]

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Using an editor to create commands

If you have a long group of commands you need to run press Ctrl-X, followed by Ctrl-E This will open your default editor.  When you’re done close the editor (saving the file) and the command will run.

Print the total bytes of files in a directory grouped by date

ls -l|awk ‘length($6)==3{x[$6″ “$7]+=$5};END{for(i in x)printf”%s:\t%d\n”,i,x[i]}’

Filter duplicate lines from a sorted files

cat list-1 list-2 list-3 | sort | uniq > final.list

Debugging bash scripts

Debugg bash scripts by runing with option -x example bash -x scriptname.sh

lowercase filen names

#! /bin/bash DIR=$1 for a in `ls $DIR` do fname=`echo $a | tr A-Z a-z` mv $DIR/$a $DIR/$fname done; exit 0

bashprofile

# .bash_profile # Get the aliases and functions if [ -f ~/.bashrc ]; then . ~/.bashrc fi # User specific environment and startup programs PATH=$PATH:$HOME/bin:/sbin export JAVA_HOME=/usr/java/jdk1.6.0_05/bin/java export PATH=$PATH:/usr/java/jdk1.6.0_05/bin export HISTIGNORE=”&” export EDITOR=nano export PATH unset USERNAME alias rm=’rm -i’ alias cp=’cp -i’ alias ls=’ls –color’ alias zf=’zf.sh’ echo -e “\033[36m########################## \033[0m” echo -e “\033[36mServer $HOSTNAME \033[0m” echo -e “\033[36mWelcome back $USER \033[0m” echo -e “\033[36musers loggged in: \033[0m” echo -e “\033[36m `users ` \033[0m” echo -e “\033[36m`uptime` \033[0m” echo […]

bashrc

Here is my typical .bashrc file # .bashrc # Source global definitions if [ -f /etc/bashrc ]; then . /etc/bashrc fi # append commenads to bash_history (when using more then one window) shopt -s histappend PROMPT_COMMAND=’history -a’ # User specific aliases and functions PATH=$PATH:$HOME/bin:/sbin #export JAVA_HOME=/usr/java/jdk1.6.0_05/bin/java export HISTIGNORE=”&” export EDITOR=nano export PATH unset USERNAME #function PWD { #pwd | awk -F\/ ‘{print $(NF-1),$(NF)}’ | sed ‘s/ /\\//’ #} #export PS1=”\[\033[0;32m\]\u@\h \[\033[33m\]\$(pwd 3)\[\033[0m\] \$ “;