Perl组合技：sub

毋容置疑，编程的分分合合是很重要的思想。

就像下面的文件一样：

use File::Spec::Functions;
use strict;


################################
################################
# routines for Debug output
#
sub DEBUG_Activate 
 {
	open (DEBUG_CHANNEL , ">&STDOUT") or LOG_MsgExit ("Failed to attempt to open STDERR channel") ;

 }

sub DEBUG_Disable
 {
	
	open (DEBUG_CHANNEL , File::Spec->devnull() ) or LOG_MsgExit ("Failed to attempt to open NULL device");
 }

sub DEBUG_Write
 {
  	print DEBUG_CHANNEL ">>$_[0]\n";
        
 }

sub DEBUG_Close
 {
   close(DEBUG_CHANNEL);
 }



###########################################
###########################################
# Routines for dealing with the logfile
sub LOG_Disable 
 {
  open (LOGFILE, ">&STDOUT") or LOG_MsgExit ("Failed to attempt to open STDOUT device");
  DEBUG_Write ("Log messages output will be redirected to STDOUT");
 }

sub LOG_Create
 {
  my $file;

	$file=$_[0];
	open (LOGFILE,">$file") or LOG_MsgExit("Cannot create the logfile $file");
        close(LOGFILE);
        DEBUG_Write("Logfile $file has been created"); 
 }

##############################33
# returns 1 if file is writable, otherwise returns 0
# if cannot write, try to create it, and if success, then returns 1
#
sub LOG_IsLOGFILEWritable
 {
  my $file;
  my $k;

  	$file = $_[0];

	if ( -w $file ) {  return 1;  }
        else {  
               	$k = open(LOGFILE,">>$file");
                if ($k) { close(LOGFILE); return 1;}
                else { return 0; }
                
            }
 }

##########################################################
# Activates the channel LOGFILE, so print to this channel
# means write in the specified logfile
sub LOG_Enable
 {
  my $file;

 	$file = $_[0];
       utime(time(),time(),$file);

	open (LOGFILE , ">>$file") or LOG_MsgExit ("Failed to attempt to open the logfile $file");
	DEBUG_Write ("Opened the logfile: $file");
 }

sub LOG_Close
 { 
  close(LOGFILE);
 }

sub LOG_Msg 
 {
  my $t;
$t=localtime();

  print LOGFILE   "$t : $_[0]\n";
  DEBUG_Write ("Logged this alarm...: $_[0]");

 }

sub LOG_MsgExit
 {
 my $t;

$t=localtime();
  print LOGFILE "$t : $_[0]\n";
  DEBUG_Write("$_[0]");
  exit;
 }

return 1;

很明显这是一个.pm 的文件， 是.pl的模块，他们的关系就像：

.html - - .css ， .pl - - .pm

顿悟了吗

这里有好多的sub 函数，供随时调用（当然这里只举了个关于 logfile 的例子）.

每一个sub函数，就相当于一个基本技，在主函数中进行组合，就是组合技，那么你就可以放肆地连招了。

PS：转载请注明出处，作者No. Liu