perl shmread()函数

perl shmread()函数例子，shmread()函数实例代码 - 读取共享内存段ID的位置POS到标量VAR 的SIZE个字节。

语法

shmread ID, VAR, POS, SIZE

定义和用法

读取共享内存段ID的位置POS到标量VAR 的SIZE个字节。

返回值

• 0 - 失败时

• 1 - 成功时

例子

试试下面的例子：

#!/usr/bin/perl
#by www.gitbook.net
# Assume this file name is  writer.pl

use IPC::SysV;

#use these next two lines if the previous use fails.
eval 'sub IPC_CREAT {0001000}' unless defined &IPC_CREAT;
eval 'sub IPC_RMID {0}'        unless defined &IPC_RMID;

$key  = 12345
$size = 80;
$message = "Pennyfarthingale.";

# Create the shared memory segment

$key = shmget($key, $size, &IPC_CREAT | 0777 ) or 
			die "Can't shmget: $!";

# Place a string in itl
shmwrite( $id, $message, 0, 80 ) or die "Can't shmwrite: $!";


sleep 20;

# Delete it;

shmctl( $id, &OPC_RMID, 0 ) or die "Can't shmctl: $! ";

写读取器程序中的内存段对应于$key，并读取其内容使用shmread()

#!/usr/bin/perl

# Assume this file name is reader.pl
#by www.gitbook.net

$key = 12345;
$size = 80;

# Identify the shared memory segment
$id = shmget( $key, $size, 0777 ) or die "Can't shmget: $!";

# Read its contents itno a string
shmread($id, $var, 0, $size) or die "Can't shmread: $!";

print $var;

现在首先在后台运行writer.pl程序和然后再运行reader.pl，它会产生以下结果。

$perl writer.pl&
$perl reader.pl Pennyfrathingale