Tcl pass args "as is" to proc

Question

I want to send the command

exp_send -i $sid -- "yes\r"

to a function that will exec the command and check errors as well. should be :

catch {exp_send -i $sid -- "yes\r"}

where :

[catch {$cmd [join $args]}

what wrong in this code :

package require Expect

proc ErrorDetector {cmd args} {

    global res

    if { [catch {$cmd [join $args]} results] } {
       puts "Connection Could not open for exp_send\n $results"
       return -level 0 0
     }

    puts sion.
}


global spawn_id
set sid [spawn cmd.exe]
exp_send {ssh [email protected]}


ErrorDetector exp_send -i $sid -- "yes\r"

the comamnd:

$cmd [join $args]

is not running as:

$cmd [join $args]

Answer 1

If you have a recent enough version of Tcl behind Expect, you can do:

$cmd {*}$args

Otherwise, with older versions of Tcl (8.4 and before) the right way to do it is one of these:

eval [list $cmd] $args
# Paranoid version: eval [list $cmd] [lrange $args 0 end]

eval [linsert $args 0 $cmd]

All the above will precisely preserve the words that you gave as arguments to your procedure. Things with join will not; that command is particularly for creating things like human-readable lists of things and for working with old-style “database” records such as you'd find in a Unix password database.