tcl - how to get the parent process id in expect script?

Question

I want to know the parent processs id of the parent inside expect script how would i do it.

I used tried to use and got this error

[sesiv@itseelm-lx4151 ~]$ invalid command name "id"
    while executing
"id process parent "
    invoked from within
"set parent_process_id [ id process parent ]"

also tried to do

 puts "parent is ---$env(PPID)**"

but it gave me this

[sesiv@itseelm-lx4151 ~]$ can't read "env(PPID)": no such variable
    while executing
"puts "parent is ---$env(PPID)**""

Answer 1

The id command is part of the Tclx package, you need to include it:

package require Tclx

Update

Since your system does not have the Tclx package, and based on your prompt, I guess you are running a Unix-like operating system, I am going to offer a solution which employs the ps command. This solution will not work under Windows.

# Returns the parent PID for a process ID (PID)
# If the PID is invalid, return 0
proc getParentPid {{myPid ""}} {
    if {$myPid == ""} { set myPid [pid] }
    set ps_output [exec ps -o pid,ppid $myPid]

    # To parse ps output, note that the output looks like this:
    #   PID  PPID
    #   4584   613
    # index 0="PID", 1="PPID", 2=myPid, 3=parent pid
    set checkPid  [lindex $ps_output 2]
    set parentPid [lindex $ps_output 3]

    if {$checkPid == $myPid} {
        return $parentPid
    } else {
        return 0
    }
}

# Test it out    
set myPid [pid]
set parentPid [getParentPid]

puts "My PID: $myPid"
puts "Parent PID: $parentPid"