Read Bash environment variable in TCL

How to read a shell environment variable in your Tcl script. So anyone开发者_JAVA技巧 please help me. I am very new in TCL.

Use $::env to access any environment variables e.g. to access the TMP environment variable do this:

set tmpdir $::env(TMP)

More info here http://wiki.tcl.tk/1624

$ export var=42
$ tclsh
% puts $env(var)
42

Environment variables are accessible via the built-in global variable env (fully qualified it is ::env). You use this like any other Tcl array.

If you want to print a list of all environment variables you can use something like this:

proc dump_env_vars {} {
    foreach name [array names ::env] {
        puts "$name == $::env($name)"
    }
}

Of course, to access just a single variable you use it like any other array, for example:

puts "HOME = '$::env(HOME)'"

For more information see the env page on the Tcler's wiki and the env section of the tclvars man page

To read a shell environment variable in Tcl script, try doing something like this:

global env
set olddisplay $env(DISPLAY)
set env(DISPLAY) unix:0

This might be expressed as well in this fashion:

set olddisplay $::env(DISPLAY)
set ::env(DISPLAY) unix:0

and forget about global.

You can check to see if the variable exists by doing something like:

if {[info exists env(VARNAME)]} {
    # okay, it's there, use it
    set value $env(VARNAME)
} else {
    # the environment var isn't set, use a default
    set value "the default value"
}

This is source.