Run this:
    puts "Type any characters, then <Return>."

    expect {
        ? {
            set result $expect_out(0,string)
            if {[string compare \n $result]} {
                scan $result %c value
                if {$value==27} {
                    puts "You just typed Esc (decimal ASCII 27)."
                } {
                    puts "You just typed '$result' (decimal ASCII $value)."
                }
            }
            exp_continue
        }
    }



Example output:  type "a<CR>", see decimal 97; type
"<F1><CR>", see the sequence





27-91-49-(49,50)-126
[[explain]]
Win 95










----
Also see "[keysyms]", CWIND [[?]], and "[How to send escape characters through Expect]".
----
[Csan] The original code did not handle the Esc $result properly - it ate the second ' character in the output.
I added a branch to handle that case.

I also extended the output to include the octal and hexadecimal values - useful for further re-use of the $result - see further on.
Another addition was to save the resulting character (sequence) to keyseq.dat, which can be imported into another text editor.
I find this addition very useful while using 'joe' editor...

The new version of the script (I called it keyseqs.exp):

    #!/usr/bin/expect

    puts "Type any characters followed by <Return>, wait 10 seconds or press Ctrl-C."

    expect {
        ? {
            set result $expect_out(0,string)
            if [string compare \n $result] {
                if {[catch {eof $fd}]} {
                  set fd [open keyseq.dat w]
                }
                scan $result %c dvalue
                if {$dvalue==27} {
                    puts "You just typed Esc (ASCII octal  033, decimal  27, hexadecimal 1B)."
                } {
                    puts "You just typed '$result' (ASCII octal [format %4s [format %#o $dvalue]], decimal [format %3s $dvalue], hexadecimal [format %x $dvalue])."
                }
                puts -nonewline $fd $result
            } {
              if {![catch {eof $fd}]} {
                close $fd
                puts "Character (sequence) written to keyseq.dat (after flushing the file contents)."
                puts "\nType any characters followed by <Return>, wait 10 seconds or press Ctrl-C."
              }
            }
            exp_continue
        }
    }

Example output (I typed PageUp):

 # ./keyseqs.exp
 Type any characters followed by <Return>, wait 10 seconds or press Ctrl-C.
 ^[[5~
 You just typed Esc (ASCII octal  033, decimal  27, hexadecimal 1B).
 You just typed '[' (ASCII octal 0133, decimal  91, hexadecimal 5b).
 You just typed '5' (ASCII octal  065, decimal  53, hexadecimal 35).
 You just typed '~' (ASCII octal 0176, decimal 126, hexadecimal 7e).
 Character (sequence) written to keyseq.dat (after flushing the file contents).

 Type any characters followed by <Return>, wait 10 seconds or press Ctrl-C.
 #












----
[LV] says:  "Believe it or not, there is no set standard for what function keys generate.
In fact, depending on the application, the same function key could generate
different values on some systems."