Exploring Expect

Environment Variables

The global array env is pre-initialized so that each element corresponds to an environment variable. For example, the path is a list of directories to search for executable programs. From the shell, the path is stored in the variable PATH. When using Tcl, the path is contained in env(PATH). It is manipulated just like any other variable.

tclsh> set env(PATH)
/usr/local/bin:/usr/bin:/bin
tclsh> set env(PATH) ".:$env(PATH)"    ;# prepend current dir
.:/usr/local/bin:/usr/bin:/bin

Modifications to the env array do not affect the parent environment, but new processes that are created (using exec, for instance) will inherit the current values (including any new elements that have created).