Ubuntu Manpage: IPC::SharedMem - SysV Shared Memory IPC object class

Provided by: perl-doc_5.18.2-2ubuntu1.7_all

NAME

       IPC::SharedMem - SysV Shared Memory IPC object class

SYNOPSIS

           use IPC::SysV qw(IPC_PRIVATE S_IRUSR S_IWUSR);
           use IPC::SharedMem;

           $shm = IPC::SharedMem->new(IPC_PRIVATE, 8, S_IRWXU);

           $shm->write(pack("S", 4711), 2, 2);

           $data = $shm->read(0, 2);

           $ds = $shm->stat;

           $shm->remove;

DESCRIPTION

       A class providing an object based interface to SysV IPC shared memory.

METHODS

new ( KEY , SIZE , FLAGS )
Creates a new shared memory segment associated with "KEY". A new segment is created if

• "KEY" is equal to "IPC_PRIVATE"

• "KEY" does not already have a shared memory segment associated with it, and "FLAGS & IPC_CREAT"
is true.

On creation of a new shared memory segment "FLAGS" is used to set the permissions. Be careful not to
set any flags that the Sys V IPC implementation does not allow: in some systems setting execute bits
makes the operations fail.

id Returns the shared memory identifier.

read ( POS, SIZE )
Read "SIZE" bytes from the shared memory segment at "POS". Returns the string read, or "undef" if
there was an error. The return value becomes tainted. See shmread.

write ( STRING, POS, SIZE )
Write "SIZE" bytes to the shared memory segment at "POS". Returns true if successful, or false if
there is an error. See shmwrite.

remove
Remove the shared memory segment from the system or mark it as removed as long as any processes are
still attached to it.

is_removed
Returns true if the shared memory segment has been removed or marked for removal.

stat
Returns an object of type "IPC::SharedMem::stat" which is a sub-class of "Class::Struct". It provides
the following fields. For a description of these fields see you system documentation.

uid
gid
cuid
cgid
mode
segsz
lpid
cpid
nattach
atime
dtime
ctime

attach ( [FLAG] )
Permanently attach to the shared memory segment. When a "IPC::SharedMem" object is attached, it will
use memread and memwrite instead of shmread and shmwrite for accessing the shared memory segment.
Returns true if successful, or false on error. See shmat.

detach
Detach from the shared memory segment that previously has been attached to. Returns true if
successful, or false on error. See shmdt.

addr
Returns the address of the shared memory that has been attached to in a format suitable for use with
"pack('P')". Returns "undef" if the shared memory has not been attached.

AUTHORS

       Marcus Holland-Moritz <mhx@cpan.org>

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