From c59b49203834348ecfb256350d574f395d84606c Mon Sep 17 00:00:00 2001
From: Alexander Sulfrian <alexander@sulfrian.net>
Date: Fri, 11 Jan 2013 03:49:26 +0100
Subject: add some more comments

---
 net_if | 22 ++++++++++++++++++----
 1 file changed, 18 insertions(+), 4 deletions(-)

diff --git a/net_if b/net_if
index dead89f..f2f1d31 100755
--- a/net_if
+++ b/net_if
@@ -17,7 +17,8 @@ my %nagios = (
 # Print nagios compatible status message and terminat script
 # with apropiate return code.
 #
-# parameter: type of message
+# parameter:
+#     type of message
 sub msg ($@) {
     my $type = shift;
     my ($msg, $exit) = @{$nagios{$type}};
@@ -31,25 +32,32 @@ sub msg ($@) {
 # This resolves interfaces groups, but only return the interfaces
 # that are up.
 #
-# parameter: list of interfaces
+# parameter:
+#     list of interfaces
 sub get_if_status (@) {
     my (@up, @down, @error);
 
     while (@_) {
+        # untaint interface name
         my $if = shift @_;
         next unless ($if =~ m/^([-\w]+)$/);
         $if = $1;
 
+        # We are doing an two step process. First we do a fork and
+        # after that we exec the ifconfig child process. This is
+        # necessary to pipe stderr of the child process away, while
+        # using the list syntax for open and exec.
         my $pid = open(IFCONFIG, "-|");
         msg('crit', "fork: $!") unless defined $pid;
 
         if ($pid == 0) {
-            # child
+            # redirect stderr
             open(STDERR, ">", "/dev/null");
             exec("ifconfig", $if)
         }
 
         while (<IFCONFIG>) {
+            # parse ifconfig output:
             if ($_ =~ m/^([-a-v0-9]+): flags=([0-9]+)</) {
                 if ($2 & 1) {
                     push(@up, $1);
@@ -68,7 +76,8 @@ sub get_if_status (@) {
 
 # Get the byte conters for incomming and outgoing packages.
 #
-# parameter: interface name
+# parameter:
+#     interface name
 sub get_if_stats ($) {
     my $if = shift;
     my $stats = {};
@@ -95,6 +104,11 @@ sub get_if_stats ($) {
 
 # Print nagios compatible message containing the number of interfaces
 # and performance data containing the byte counter for the interfaces.
+#
+# parameter:
+#     nagios status code
+#     additional message
+#     interface statistics
 sub print_stats ($) {
     my $stats = shift;
     my ($count, $perfdata);
-- 
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