text-processing

Credentials or any other sensitive data should never be stored in configuration files (e.g. Terraform, Dockerfile, Kubernetes YAML files, etc.) and of course should never be committed to Git repositories.

Much better practice is to set some placeholders inside such files, and when needed, replace them with values from your environment variables, that can be done, for example, using a envsubst command.

In this post you will find how to install the envsubst command and examples of how to use it to replace environment variables in the files. (more…)

If you use vi/vim text editor in a terminal with a dark background it may be hard to read some text due to improperly configured color scheme.

For example, dark-blue comments on a black background in vi/vim make them almost unreadable.

By default, vi/vim is configured to work with a light background, i.e. has a set background=light setting.

If you use the dark background in your terminal, you need to change the background setting in vi/vim, that will lead to adjustment of a color scheme to the dark background and make the text readable.

This short note shows how to fix colors on the dark background in vi/vim. (more…)

A newline (also known as a line ending, end of line (EOL) or line break) is a character used to represent the end of a line of text and the beginning of a new line.

Text files created on DOS/Windows machines have different line endings than files created on Unix/Linux.

This note shows how to find out the line endings in a text file and how to change them. (more…)

If you try to delete characters in the insert mode with the backspace key in vi/vim text editor, this sometimes may not work.

Even though this is not a bug but a feature of vi/vim, you may still want to fix a backspace that is “not working”.

In this small note i will show how to fix “not working” backspace key in the insert mode in vi/vim. (more…)

By default, vi/vim text editor uses the h, j, k and l keys for navigation.

Hitting arrow keys in the insert mode will insert newlines and print A, B, C, D capital letters.

In this small note i will show how to fix not working arrow keys, that print letters in the insert mode in vi/vim. (more…)

From time to time it is required to modify some file very fast.

And it goes without saying that the most popular command line tools for this in Linux are sed and awk – the two best text processing programs.

In the following article, you’ll find an information about how to add some text, character or comma to the beginning or to the end of every line in a file using sed and awk. (more…)

From the following article, you’ll learn how to remove first characters from the beginning of each line in Bash and how to print strings between first and last characters using cut command.

You’ll also learn how to remove last characters of each line using trick with reverse command.

I’ve created a file with the following content and I’ll use it in examples below. So lets say we need to remove first and last characters of each line from the given file.

$ cat file
12345===I Love Bash===54321
12345===I Love Bash===54321
12345===I Love Bash===54321

Remove First N Characters Of Each Line

Use the following command to delete first 5 characters of each line (trim first 5 characters and print each line starting from the 6th character):

$ cat file | cut -c 6-
===I Love Bash===54321
===I Love Bash===54321
===I Love Bash===54321

Print Strings Between First and Last Characters

Use the following command to print strings between 9th and 20th characters of each line in Bash:

$ cat file | cut -c 9-20
I Love Bash
I Love Bash
I Love Bash

Print First N Characters Of Each Line

Use the following command to print first 20 characters of each line in Bash:

$ cat file | cut -c 1-20
12345===I Love Bash
12345===I Love Bash
12345===I Love Bash

Remove Last Character Of Each Line

Using combination of reverse and cut commands we can remove last N characters of each line, as shown below. (source)

Use the following command to delete last character of each line in Bash:

$ rev file | cut -c 2- | rev
12345===I Love Bash===5432
12345===I Love Bash===5432
12345===I Love Bash===5432

Remove Last N Characters Of Each Line

Use the following command to delete last 8 characters of each line in Bash:

$ rev file | cut -c 9- | rev
12345===I Love Bash
12345===I Love Bash
12345===I Love Bash