转自:http://www.yiibai.com/perl/perl_semctl.html
描述
perl semctl()函数例子,semctl()函数实例代码 - 控制系统V信号量。
语法
semctl ID, SEMNUM, CMD, ARG |
定义和用法
控制系统V信号量。 你将需要进口IPCSysV的模块,以获得正确的定义CMD。 该函数调用系统调用semctl()函数。
返回值
-
undef - 失败时
-
0 但真(true)成功时
例子
试试下面的例子:创建一个信号量,增加它的值
#!/usr/bin/perl -w # Assume this file nam eis left.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_EXCL {0002000}' unless defined &IPC_EXCL; eval 'sub IPC_RMID {0}' unless defined &IPC_RMID; $key = 1066; $| = 1; $num = 0; $flag = 0; # Create the semaphor - by www.yiibai.com $id = semget ( $key, 1, &IPC_EXCL|&IPC_CREAT|0777 ) or die "Can't semget: $!"; foreach( 1..5) { $op = 0; $operation = pack( "s*", $num, $op, $flags ); semop( $id, $operation ) or die "Can't semop: $! "; print "Left....\n"; sleep 1; $op = 2; $operation = pack( "s*", $num, $op, $flags ); # add 2 to the semaphore ( now 2 ) semop( $id, $operation ) or die "Can't semop $! "; } semctl ( $id, 0, &IPC_RMID, 0 );
运行上面的程序中使用$left.pl& 背景,并写另一个程序。 在这里留下左键设置为2信号和右键打印右键和复位信号为0。这种情况持续下去,直到左键完成其循环后,它破坏了semctl()信号。
#!/usr/bin/perl -w # Assume this file name is right.pl $key = 1066; $| = 1; $num = 0; $flags = 0; # Identify the semaphore created by left. $id = semget( $key, 1, 0 ) or die ("Can't semgt : $!" ); foreach( 1..5){ $op = -1; $operation = pack( "s*", $num, $op, $flags ); # Add -1 to the semaphore (now 1) semop( $id, $operation ) or die " Can't semop $!"; print "Right....\n"; sleep 1; $operation = pack( "s*", $num, $op, $flags ); # Add -1 to the semaphore (now 0) semop( $id, $operation ) or die "Can't semop $! "; }
现在运行right.pl,它会产生以下结果:
Right....
Left....
Right....
Left....
Right....
Left....
Right....
Left....
Right....
Left....