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 SysV IPC in perlipc, IPC::SysV
, IPC::Semaphore
documentation.
Portability issues: semctl in perlport.
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