The snmp# walk session command walks a whole MIB sub-tree. The command repeats sending getbulk requests until the returned varbind list is outside of the sub-tree rooted at the varbind list vbl.

The first version of the walk command is synchronous. For each valid varbind list retrieved from the agent, the Tcl script body is evaluated. 

Before evaluation of body starts, the actual varbind list is assigned to the variable named varName. 

Below is a simple example that prints the two columns ifDescr and ifType of the interface table:

$s walk x “IF-MIB!ifDescr IF-MIB!ifType” {
    puts “[snmp value $x 0] ([snmp value $x 1])”
 }

The second version of the walk command is asynchronous. For each valid varbind list retrieved from the agents, the callback script script is evaluated. 

Substitutions of % escape sequences take place as described above and scripts are always evaluated at global level. 

The script is called with an error status set to endOfWalk and an empty varbind list when the walk terminates. 

Below is the asynchronous version of the example which prints the two columns ifType and ifDescr of the interface table:

$s walk “IF-MIB!ifDescr IF-MIB!ifType” {
if {”%E” == “noError”} { 
    puts [subst {[snmp value “%V” 0] ([snmp value “%V” 1])}]
 }
 }