Execute in Parallel and Wait
fileevent is often recommended for execution of multiple processes in parallel, but it requires a script to be written in an event-driven style. Sometimes what is wanted is simple exec-style semantics, but with multiple processes executing in parallel. Here is an example of that:
#! /bin/env tclsh
proc main {} {
for {set i 0} {$i < 5} {incr i} {
set script {
#simulate a hard-working process
for {set i 0} {$i < 10000000} {incr i} {
}
puts [list hello from [pid]]
}
set chan [open |[list [info nameofexecutable] <<$script 2>@stderr]]
dict set res $chan command $script
fconfigure $chan -blocking 0
lappend background $chan
}
while 1 {
foreach chan $background {
if {[eof $chan]} {
if {[set idx [lsearch -exact $background $chan]] >= 0} {
set background [lreplace $background $idx $idx]
}
catch [close $chan] cres copts
dict set res $chan result $cres
dict set res $chan options $copts
} else {
puts -nonewline [read $chan]
}
}
if {[llength $background] == 0} {
break
}
after 100
}
return $res
}
#puts [main]
mainIn contrast with some other solutions, TclX's wait, this example does not require any extension, and should work on various platforms.