shmread
优质
小牛编辑
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2023-12-01
描述 (Description)
此函数将共享内存段ID读取到POS位置的标量VAR中,最多为SIZE字节。
语法 (Syntax)
以下是此函数的简单语法 -
shmread ID, VAR, POS, SIZE
返回值 (Return Value)
此函数在失败时返回0,在成功时返回1。
例子 (Example)
以下是显示其基本用法的示例代码 -
#!/usr/bin/perl
# 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: $! ";
编写一个读取程序,该程序检索与$ key对应的内存段,并使用shmread();读取其内容。
#!/usr/bin/perl
# Assume this file name is reader.pl
$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,然后在reader.pl中运行,然后它将产生以下结果。
$perl writer.pl&
$perl reader.pl
Pennyfrathingale