panel 1: every process has environment variables

how to see any process’s environment variables on Linux:

cat /proc/$PID/environ | tr '\0' '\n'

panel 2: shell scripts have 2 kinds of variables

1. environment variables
2. shell variables

unlike in most languages, in shell you access both of these in the exact same way: $VARIABLE

panel 3: export sets environment variables

export ANIMAL=panda

export ANIMAL=panda means that every child process will have ANIMAL set to panda

panel 4: child processes inherit environment variables

this is wy the variables set in your .bash_profile work in all programs you start from the terminal. They’re all child processes of your bash shell!

panel 5: shell variables aren’t inherited

var=panda

in this example, $var only gets set in this process, not in child processes

panel 6: you can set environment variables when starting a program

env VAR=panda ./myprogram

This sets VAR to panda in myprogram’s environment (but not in the current shell).