How to loop a variable in tcl

Question

I am new to tcl. I have some doubt regarding can i loop a variable in tcl.

I have set variable called handle ie

set handle [pcap open -ip 192.168.1.3] 

This creates a handle pcap0. I wanna know whether can i loop this variable in tcl so that at a time i can create a ten handles.

Answer 1

You have two options: lists and arrays.

1. Using a list

In Tcl, a list is a value that contains a sequence of other (arbitrary) values. You can add things to the end of a list in a variable with lappend , and iterate over the list with foreach .

foreach ipaddress {192.168.1.3 192.168.1.4 192.168.1.5 ...} {
    lappend handles [pcap open -ip $ipaddress]
}

foreach handle $handles {
    # Do something with $handle here
}

2. Using an array

In Tcl, an array is a composite variable backed by an associative map (you look things up by any value you want, not necessarily a number). They can work quite well with lists.

set the_addresses {192.168.1.3 192.168.1.4 192.168.1.5 ...}
foreach ipaddress $the_addresses {
    set handle($ipaddress) [pcap open -ip $ipaddress]
}

foreach ipaddress $the_addresses {
    # Do something with $handle($ipaddress) here
}

Which option is best depends on the details of what you are doing.

Answer 2

Donal gave what seemed to be the complete answer, if the IP address is the same, simply do:

set handles ""
set ipaddress 192.168.1.3
for {set i 0} {$i < 10} {incr i} {
    lappend handles [pcap open -ip $ipaddress]
}

foreach handle $handles {
    # Do something with $handle here
}