From 13fd7884410510c20f77bdd1204d60a419eb7ac4 Mon Sep 17 00:00:00 2001
From: Ian Jackson <ijackson@chiark.greenend.org.uk>
Date: Sat, 9 Jun 2012 19:36:31 +0100
Subject: [PATCH] subproc

---
 applet.tcl  | 40 ------------------------------------
 example     |  3 ++-
 subproc.tcl | 59 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 61 insertions(+), 41 deletions(-)
 create mode 100644 subproc.tcl

diff --git a/applet.tcl b/applet.tcl
index 2bb9ac4..8a0193f 100644
--- a/applet.tcl
+++ b/applet.tcl
@@ -218,43 +218,3 @@ proc setupinnerwindow {w} {
 proc setimage {image} {
     .i configure -image $image
 }
-
-proc fork-then {ondeath inchild} {
-    global children errorCode errorInfo
-    foreach f {stdout stderr} {
-	if {[catch { flush $f } emsg]} {
-	    catch { bgerror $emsg }
-	}
-    }
-    set pid [fork]
-    if {!$pid} { 
-	if {[catch { 
-	    uplevel 1 $inchild
-	} emsg]} {
-	    puts stderr "CHILD ERROR $emsg\n$errorCode\n$errorInfo\n"
-	}
-	kill KILL [id process]
-    }
-    set children($pid) $ondeath
-    return $pid
-}
-
-proc chld-handler {} {
-    global children
-    while 1 {
-	if {[catch { set got [wait -nohang] }]} break
-	if {![llength $got]} break
-	manyset $got pid how how2
-	if {[info exists children($pid)]} {
-	    set l $children($pid)
-	    unset children($pid)
-	    if {[catch {
-		uplevel #0 [concat [list $l] $how $how2]
-	    } emsg]} {
-		catch { bgerror $emsg }
-	    }
-	}
-    }	
-}
-
-signal -restart trap CHLD { after idle chld-handler }
diff --git a/example b/example
index 8c5e0c9..b719c50 100755
--- a/example
+++ b/example
@@ -2,6 +2,7 @@
 # -*- Tcl -*-
 
 source applet.tcl
+source subproc.tcl
 
 #----- menu -----
 
@@ -68,7 +69,7 @@ proc run-child {} {
     }
 
     set status none
-    set status [fork-then child-died {
+    set status [subproc::fork child-died {
 	execl xacpi-simple [list -into [winfo id .i.i.b.c]]
     }]
     puts "FORKED $status"
diff --git a/subproc.tcl b/subproc.tcl
new file mode 100644
index 0000000..36d5465
--- /dev/null
+++ b/subproc.tcl
@@ -0,0 +1,59 @@
+
+namespace eval subproc {
+
+#----- general purpose subprocess handling -----
+#
+# One useful procedure:
+#    subprocess::fork ONDEATH INCHILD
+# forks, evaluates INCHILD in the calling context but in the child
+# and when the child dies evaluates [concat [list ONDEATH] W2 W3]
+# where W2 and W3 are the 2nd and 3rd elements of the list returned
+# by tclx's wait.
+#
+# INCHILD should not return; if it does or if it gets an error, the
+# result is that the child gets a SIGKILL.
+
+variable children
+
+proc fork {ondeath inchild} {
+    variable children
+    global errorCode errorInfo
+    foreach f {stdout stderr} {
+	if {[catch { flush $f } emsg]} {
+	    catch { bgerror $emsg }
+	}
+    }
+    set pid [::fork]
+    if {!$pid} { 
+	if {[catch { 
+	    uplevel 1 $inchild
+	} emsg]} {
+	    puts stderr "CHILD ERROR $emsg\n$errorCode\n$errorInfo\n"
+	}
+	kill KILL [id process]
+    }
+    set children($pid) $ondeath
+    return $pid
+}
+
+proc chld-handler {} {
+    variable children
+    while 1 {
+	if {[catch { set got [wait -nohang] }]} break
+	if {![llength $got]} break
+	manyset $got pid how how2
+	if {[info exists children($pid)]} {
+	    set l $children($pid)
+	    unset children($pid)
+	    if {[catch {
+		uplevel #0 [concat [list $l] $how $how2]
+	    } emsg]} {
+		catch { bgerror $emsg }
+	    }
+	}
+    }	
+}
+
+signal -restart trap CHLD { after idle subproc::chld-handler }
+
+}
-- 
2.30.2