public/subjects/devops/input-redirection

Input redirection

Instructions

In this exercise you will make a script input-redirection.sh. This script will read from an here document (heredoc). Usually this technique is used to programmatically generate scripts or configuration files receiving some multiline input.

The script will create a file show-info.sh that will run the command cat with -e as argument. The input to cat will be passed using heredoc. Running show-info.sh will output some useful information about three common environment variables.

Watch the videos:

• https://www.youtube.com/watch?v=oJwZgefy8nA

The environment variables are PWD, PATH and USERNAME.

Usage

• First generate the script programmatically:

$ ./input-redirection.sh
$

• Then run the generated script:

$ bash ./show-info.sh
The current directory is: current/path/example$
The default paths are: /first_path:/second_path:/third_path$
The current user is: your_name$
$

Hints

You will need to mix more than one redirection tool:

• > will be useful to create show-info.sh.

• << is the heredoc redirection.

• To start playing with heredoc you can try wc -l <<EOF, type some random things, then write EOF on a new line and press Enter.

• Don't forget you can use echo to write into show-info.sh.

You have to use Man or Google to know more about commands flags, in order to solve this exercise! Google and Man will be your friends!