In Unix and Linux systems, you can use the printenv command to print a list of all the environment variables that are set in the current shell. For example:
$ printenv
This will print a list of all the environment variables that are set in the current shell, with each variable displayed on a separate line in the format VARNAME=value.
You can also use the echo command to print the value of a specific environment variable. For example:
$ echo $VARNAME
This will print the value of the VARNAME environment variable.
Alternatively, you can use the env command to list all the environment variables and their values. For example:
$ env
This will print a list of all the environment variables and their values, with each variable displayed on a separate line in the format VARNAME=value.
You can also use the set command to list all the variables that are set in the current shell, including both environment variables and shell variables. For example:
$ set
This will print a list of all the variables that are set in the current shell, with each variable displayed on a separate line.
It is also possible to use various shell expansion operators to extract specific pieces of information from the environment variables. For example, you can use the ${VARNAME:-default} operator to print the value of the VARNAME environment variable, or a default value if the variable is not set.
For more information about environment variables and shell expansion operators in Unix and Linux, you may want to refer to the documentation for your specific shell, or consult a Unix or Linux reference guide.