set, unset - Set or unset shell variables
set [ name=value… ]
With no arguments, set lists all shell variables and their values. With arguments, set assigns a value to the variable name given.
Sets the variable hello to the value “world”. To access the value in this new variable, prefix it with a dollar sign, as in:
1% echo $hello world 2% ls $hello world: directory not found
Multiple variables can be assigned all at once, as with:
set foo=bar seven=7 hard="disk drive"
To erase a variable, the unset command is used with one or more variable names:
3% unset hello 4% unset crash bang bigbang bam
Note that variables used in the value portion of a set command are expanded into the value. This may not be desirable. In the case where the variable should not be expanded during the assignment, escape the variable with a backslash (\):
set prompt="[\$cwd] "