TCL: how to check if environment variable already set

Question

I am trying to construct a module file and I would like to include an if statement to check whether certain environment variables (e.g. PATH, LD_LIBRAY_PATH, PYTHON_PATH, ...) have already been set.

I have tried several different syntax options (after searching on here, official documentation and other forums) but when I then try:

module use modulefiles
module load mymodule

I keep getting ERROR:102: Tcl command execution failed error. Here are a few of the options that I have tried:

i)

set myTools /path/to/my/Tools
if { info exists $LD_LIBRARY_PATH } {
    setenv LD_LIBRARY_PATH $myTools/lib:$myTool/lib64:$LD_LIBRARY_PATH
} else {
    setenv LD_LIBRARY_PATH $myTools/lib:$myTools/lib64
}

ii)

set myTools /path/to/my/Tools
if { [info exists $LD_LIBRARY_PATH] } {
    setenv LD_LIBRARY_PATH $myTools/lib:$myTool/lib64:$LD_LIBRARY_PATH
} else {
    setenv LD_LIBRARY_PATH $myTools/lib:$myTools/lib64
}

iii)

set myTools /path/to/my/Tools
if { $?LD_LIBRARY_PATH } {
    setenv LD_LIBRARY_PATH $myTools/lib:$myTool/lib64:$LD_LIBRARY_PATH
} else {
    setenv LD_LIBRARY_PATH $myTools/lib:$myTools/lib64
}

What is the correct syntax to check for the existence of environment variables that may have already been set, e.g. in a .cshrc or .login file?

Apologies if this is a basic question. I've done stuff like this before in the shell (mainly csh), but I am new to TCL and building module files, so any help and advice wold be greatly appreciated!

Thanks!

Answer 1

The http://wiki.tcl.tk/1624 about env contains probably the answer to your question.

Following the hints given in the other answers and the wiki link given above I constructed following code which works for me.

if { [info exists ::env(IDL_PATH)] } {
   if {![string match *<IDL_DEFAULT>* $::env(IDL_PATH)]} {
   puts stderr "Warning: ill defined IDL_PATH environment variable
   }
} else {
setenv  IDL_PATH        "<IDL_DEFAULT>"
}