Exam 102-500 Topic 2 Question 7 Discussion

The set command lists all defined variables and functions within Bash, including local, environment, and shell variables, as well as aliases and functions. The output of set can be very long, so it is often piped to less, grep, or other commands for filtering or paging. The set command can also be used to set or unset shell options and positional parameters. The -o posix option to set limits the output to only variables, as defined by the POSIX standard123.
The env command lists only the environment variables, which are a subset of the shell variables that are passed to child processes. The env command can also be used to run a command in a modified environment, or to print or set environment variables. The -a option to env is not valid in most implementations45.
The echo command prints a line of text to the standard output. The $ENV variable is not a predefined variable in Bash, but it can be set by the user or by other programs. If it is not set, echo $ENV will print a blank line1 . References: