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Perl in a Nutshell

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Function Reference
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semctl

semctl id, semnum, cmd, arg

Calls the System V IPC system call semctl(2). If cmd is &IPC_STAT or &GETALL, then arg must be a variable which will hold the returned semid_ds structure or semaphore value array. The function returns like ioctl: the undefined value for error, 0 but true for zero, or the actual return value otherwise. On error, it puts the error code into $!. Before calling, you should say:

require "ipc.ph";
require "sem.ph";
This function is available only on machines supporting System V IPC.


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Reference: selectBook IndexReference: semget