replace space with underscore in expect script

Question

#!/usr/bin/expect -f
set cmd "abc def ghi lkj"
set log [ expr echo ${cmd// /_} ]

I would like to log variable as ghi_lkj

first I wast trying to replace all spaces with underscores and then remove first two words.

I want to do it only in expect script not shell script.

please suggest how to do. Thanks in Advance.

Answer 1

expect is a TCL interpreter, ${cmd// /_} is a Korn shell parameter expansion operator. TCL is not ksh, or any shell for that matters.

After reading the expect man page, your next step should be to study the TCL documentation. See for instance https://tcl.tk/doc/ though you can also install the man pages on your system for your version of TCL (you may need to install a tcl-doc package).

Here to do character substitutions, you can use TCL's string map for instance:

set cmd "abc def ghi lkj"
set log [string map {" " _} $cmd]
puts $log

Or consider that $cmd as a list and join with _:

set cmd "abc def ghi lkj"
set log [join $cmd _]
puts $log

Which would output abc_def_ghi_lkj.

If you want ghi_lkj, then, that's not only SPC to _ you want to do.

Possibly you want the last two words joined with _ or all but the first 2 joined with _:

set cmd "abc def ghi lkj"
set log [join [lrange $cmd 2 end] _]
puts $log