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public/subjects/devops/set-env-vars/README.md

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set-env-vars

Instructions

Create a script set-env-vars.sh, which will allow you to set the following variables as environment variables and and print them all:

  • MY_MESSAGE which contains the string "Hello World".
  • MY_NUM which contains the number 100.
  • MY_PI which contains the number 3.142.

Expected output:

$ printenv  # The env variables present are just an example, yours will be different.
SHELL=/bin/bash
TERM=xterm
USER=demouser
LS_COLORS=rs=0:di=01;34:ln=01;36:mh=00:pi=40;33:so=01;35:do=01;35:bd=40;33;01:cd=40;33;01:or=40;31;01:su=37;41:sg=30;43:ca:...
MAIL=/var/mail/demouser
PATH=/usr/local/bin:/usr/bin:/bin:/usr/local/games:/usr/games
PWD=/home/demouser
LANG=en_US.UTF-8
SHLVL=1
HOME=/home/demouser
LOGNAME=demouser
LESSOPEN=| /usr/bin/lesspipe %s
LESSCLOSE=/usr/bin/lesspipe %s %s
_=/usr/bin/printenv
$ ./set-env-vars.sh
MY_NUM=100
SHELL=/bin/bash
TERM=xterm
USER=demouser
LS_COLORS=rs=0:di=01;34:ln=01;36:mh=00:pi=40;33:so=01;35:do=01;35:bd=40;33;01:cd=40;33;01:or=40;31;01:su=37;41:sg=30;43:ca:...
MAIL=/var/mail/demouser
PATH=/usr/local/bin:/usr/bin:/bin:/usr/local/games:/usr/games
PWD=/home/demouser
LANG=en_US.UTF-8
MY_PI=3.142
SHLVL=1
HOME=/home/demouser
LOGNAME=demouser
MY_MESSAGE=Hello World
LESSOPEN=| /usr/bin/lesspipe %s
LESSCLOSE=/usr/bin/lesspipe %s %s
_=/usr/bin/printenv
$

Hints

Setting values to environment variables

In order to set a value to an existing environment variable, we use an assignment expression. For instance, to set the value of the "LANG" variable to "he_IL.UTF-8", we use the following command:

$ LANG=he_IL.UTF-8

If we use an assignment expression for a variable that doesn't exist, the shell will create a shell variable, which is similar to an environment variable but does not influence the behaviour of other applications.

A shell variable can be exported to become an environment variable with the export command. To create the "EDITOR" environment variable and assign the value "nano" to it, you can do:

$ EDITOR=nano
$export EDITOR

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!