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Perl Language Reference Manual
by Larry Wall and others
Paperback (6"x9"), 724 pages
ISBN 9781906966027
RRP £29.95 ($39.95)

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semctl ID,SEMNUM,CMD,ARG

Calls the System V IPC function semctl(2). You'll probably have to say

use IPC::SysV;

first to get the correct constant definitions. If CMD is IPC_STAT or GETALL, then ARG must be a variable that will hold the returned semid_ds structure or semaphore value array. Returns like ioctl: the undefined value for error, "0 but true" for zero, or the actual return value otherwise. The ARG must consist of a vector of native short integers, which may be created with pack("s!",(0)x$nsem). See also 20.8, IPC::SysV, IPC::Semaphore documentation.

ISBN 9781906966027Perl Language Reference ManualSee the print edition