print out the environment
printenv prints out the names and values
of the variables in the environment, with one name/value pair per line. If
name is specified, only its value is printed.
If a name is specified and it is not defined
in the environment,
printenv returns exit status 1,
else it returns status 0.
csh(1), sh(1), environ(7)
printenv command first appeared in
Bill Joy, February 1979.