Like Geeks recently published an interesting series on writing Bash shell scripts:
Today we are going to talk about bash script or shell scripting actually, they are called shell scripts in general but we are going to call them bash scripts because we are going to use bash among the other Linux shells. There are zsh, tcsh , ksh and other shells, you can review the basic Linux commands before starting on bash script programming.
In the previous post, we talked about how to write a bash script. And we’ve seen how bash scripting is awesome. In this post, we continue to look at structured commands that control the flow of your shell scripts. You’ll see how you can perform repeating processes; this post demonstrates for loop, while in bash scripts
Today we will know how to retrieve input from the user and deal with that input so our script becomes more interactive.
On the previous post we’ve talked about parameters and options in detail and today we will talk about something is very important in shell scripting which is input & output & redirection.
On the last post, we’ve talked about input and output and redirection in bash scripting. Now you start building some Linux bash scripts, you may wonder how to run and control them on your Linux system. The only way we’ve run scripts is directly from the command line interface in real-time mode. This isn’t the only way to run Linux bash scripts in Linux.
If you get tired writing the same blocks of code over and over in your bash script. It would be nice to just write the block of code once and refer to that block of code anywhere in your bash script without having to rewrite it.
The bash shell provides a feature allowing you to do just that called Functions.
Bash functions are blocks of script code that you assign a name to and reuse anywhere in your code. Anytime you need to use that block of code in your script, you simply use the function name you assigned it.
We are going to talk about how to create your own bash functions and how to use them in other shell scripts.
On the previous post we’ve talked about bash functions and how to use it from the command line and we’ve seen some other cool stuff I recommend you to review it, Today we will talk about a very useful tool for string manipulation called sed, sed Linux command is one of the most common tools that people use to work with text files like log files, configuration files, and other text files. If you perform any type of data manipulation in your bash scripts, you want to become familiar with the sed and gawk tools in this post we are going to focus on sed Linux command and see its ability to manipulate text which is very important step in our bash scripting journey
On the previous post we’ve talked about sed Linux command and we’ve seen many examples of using it in text processing and how it is good in this, nobody can deny that sed is very handy tool but it has some limitations, sometimes you need a more advanced tool for manipulating data, one that provides a more programming-like environment giving you more control to modify data in a file more robust. This is where awk command comes in.
The awk command or GNU awk specifically because there are many extensions for awk out there takes stream editing one step further than the sed editor by providing a programming language instead of just editor commands.
In order to successfully working with the Linux sed editor and the awk command in your shell scripts you has to understand regular expressions or in short regex and to be accurate in our case it is bash regex, since there are many engines for regex you can use and we here in this regex tutorial will use the shell regex and see the bash power in working with regex.
First, we need to understand what regex is then we will dive deep into using it
Source: Regex tutorial for Linux
In the last post, we’ve talked about regex and we see how to use them in sed and awk for text processing and we discussed before Linux sed command and awk command. During the series, we write small shell scripts but we didn’t mix things up, I think we should take a small step and write a shell script that can be some useful.
The main reason for learning to write a shell script is to be able to create your own Linux utilities. Understanding how to write useful and practical scripts is important.
However, sometimes it helps to do something fun to learn a concept or skill. The scripts in this post they can be lots of fun! And they help empower your script writing concepts.
In the previous post we’ve talked about writing practical shell scripts and we’ve seen how it is easy to write a shell script and we’ve used most of our knowledge we’ve discussed on the previous posts, today we are going to talk about a tool that does magic to our shell scripts,that tool is expect command or expect programming language. Expect command or expect programming language is a language that talks with your interactive programs or scripts that require user interaction for input. Expect works by expecting input, and upon receiving the expected input, the Expect script will send the response without any user interaction, just like magic.