PATH and Shell Commands - serdarulutas/MADD-Notes Wiki

Introduction

printenv

printenv prints environment variables. Example:

LOGNAME=serdarulutas

USER=serdarulutas

SHLVL=1

PWD=/Users/serdarulutas

OLDPWD=/Users

export

export makes the variable available to the environment

example: Step 1: export T_SCREENS=5 Step 2: export T_NUMBER_OF_LINES=10 Step 3: printenv to verify that they are added to the variable list

Result:

GREP_COLORS=mt=37;45

T_SCREEN=5

T_NUMBER_OF_LINES=10

LANG=en_CA.UTF-8

echo

echo can be used to display environmental variables

echo T will return a blank text.

But echo $T_SCREEN will return 5, the value of the variable

Advanced topics

Exporting a variable.

  1. export MESSAGE="HELLO"
  2. export MESSAGE_COPY=$MESSAGE

Step 2 will grap the environment variable value "HELLO" and assign it to MESSAGE_COPY variable. Result is:

MESSAGE=HELLO

MESSAGECOPY=HELLO

LANG=en_CA.UTF-8

_=/usr/bin/printenv

PATH variable

echo $PATH

PATH is used as a list of places where programs are installed. When a program is demanded by user, the OS looks into each folder described in PATH.