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Michael Kerrisk
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man7/svipc.7
261
man7/svipc.7
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@ -50,48 +50,40 @@ For each resource, the system uses a common structure of type
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to store information needed in determining permissions to perform an
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ipc operation.
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The
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.B ipc_perm
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.I ipc_perm
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structure, defined by the
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.I <sys/ipc.h>
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system header file, includes the following members:
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.sp
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.B
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uid_t cuid;
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/* creator user ID */
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.br
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.B
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gid_t cgid;
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/* creator group ID */
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.br
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.B
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uid_t uid;
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/* owner user ID */
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.br
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.B
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gid_t gid;
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/* owner group ID */
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.br
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.B
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ushort mode;
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/* r/w permissions */
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.in +0.5i
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.nf
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struct ipc_perm {
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uid_t cuid; /* creator user ID */
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gid_t cgid; /* creator group ID */
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uid_t uid; /* owner user ID */
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gid_t gid; /* owner group ID */
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ushort mode; /* r/w permissions */
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};
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.fi
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.in
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.PP
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The
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.B mode
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.I mode
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member of the
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.B ipc_perm
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.I ipc_perm
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structure defines, with its lower 9 bits, the access permissions to the
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resource for a process executing an ipc system call.
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The permissions are interpreted as follows:
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.sp
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.nf
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0400 Read by user.
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0200 Write by user.
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0400 Read by user.
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0200 Write by user.
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.sp .5
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0040 Read by group.
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0020 Write by group.
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0040 Read by group.
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0020 Write by group.
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.sp .5
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0004 Read by others.
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0002 Write by others.
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0004 Read by others.
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0002 Write by others.
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.fi
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.PP
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Bits 0100, 0010, and 0001 (the execute bits) are unused by the system.
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@ -128,7 +120,7 @@ Get resource options.
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Note that
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.B IPC_PRIVATE
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is a
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.B key_t
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.I key_t
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type, while all the other symbolic constants are flag fields and can
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be OR'ed into an
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.I int
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@ -141,74 +133,58 @@ and has an associated data structure of type
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defined in
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.IR <sys/msg.h> ,
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containing the following members:
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.sp
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.B
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struct ipc_perm msg_perm;
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.br
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.B
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msgqnum_t msg_qnum;
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/* no of messages on queue */
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.br
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.B
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msglen_t msg_qbytes;
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/* bytes max on a queue */
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.br
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.B
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pid_t msg_lspid;
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/* PID of last msgsnd(2) call */
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.br
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.B
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pid_t msg_lrpid;
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/* PID of last msgrcv(2) call */
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.br
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.B
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time_t msg_stime;
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/* last msgsnd(2) time */
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.br
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.B
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time_t msg_rtime;
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/* last msgrcv(2) time */
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.br
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.B
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time_t msg_ctime;
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/* last change time */
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.in +0.5i
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.nf
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struct msqid_ds {
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struct ipc_perm msg_perm;
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msgqnum_t msg_qnum; /* no of messages on queue */
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msglen_t msg_qbytes; /* bytes max on a queue */
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pid_t msg_lspid; /* PID of last msgsnd(2) call */
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pid_t msg_lrpid; /* PID of last msgrcv(2) call */
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time_t msg_stime; /* last msgsnd(2) time */
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time_t msg_rtime; /* last msgrcv(2) time */
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time_t msg_ctime; /* last change time */
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};
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.fi
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.in
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.TP 11
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.B msg_perm
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.B ipc_perm
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.I msg_perm
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.I ipc_perm
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structure that specifies the access permissions on the message
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queue.
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.TP
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.B msg_qnum
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.I msg_qnum
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Number of messages currently on the message queue.
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.TP
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.B msg_qbytes
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.I msg_qbytes
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Maximum number of bytes of message text allowed on the message
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queue.
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.TP
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.B msg_lspid
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.I msg_lspid
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ID of the process that performed the last
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.BR msgsnd (2)
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system call.
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.TP
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.B msg_lrpid
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.I msg_lrpid
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ID of the process that performed the last
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.BR msgrcv (2)
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system call.
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.TP
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.B msg_stime
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.I msg_stime
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Time of the last
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.BR msgsnd (2)
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system call.
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.TP
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.B msg_rtime
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.I msg_rtime
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Time of the last
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.BR msgrcv (2)
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system call.
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.TP
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.B msg_ctime
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.I msg_ctime
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Time of the last
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system call that changed a member of the
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.B msqid_ds
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.I msqid_ds
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structure.
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.SS Semaphore Sets
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A semaphore set is uniquely identified by a positive integer
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@ -218,81 +194,72 @@ and has an associated data structure of type
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defined in
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.IR <sys/sem.h> ,
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containing the following members:
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.sp
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.B
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struct ipc_perm sem_perm;
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.br
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.B
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time_t sem_otime;
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/* last operation time */
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.br
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.B
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time_t sem_ctime;
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/* last change time */
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.br
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.B
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ulong sem_nsems;
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/* count of sems in set */
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.nf
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.in +0.5i
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.nf
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struct semid_ds {
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struct ipc_perm sem_perm;
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time_t sem_otime; /* last operation time */
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time_t sem_ctime; /* last change time */
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ulong sem_nsems; /* count of sems in set */
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};
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.fi
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.in
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.TP 11
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.B sem_perm
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.B ipc_perm
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.I sem_perm
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.I ipc_perm
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structure that specifies the access permissions on the semaphore
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set.
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.TP
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.B sem_otime
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.I sem_otime
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Time of last
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.BR semop (2)
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system call.
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.TP
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.B sem_ctime
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.I sem_ctime
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Time of last
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.BR semctl (2)
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system call that changed a member of the above structure or of one
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semaphore belonging to the set.
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.TP
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.B sem_nsems
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.I sem_nsems
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Number of semaphores in the set.
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Each semaphore of the set is referenced by a non-negative integer
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ranging from
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.B 0
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to
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.BR sem_nsems\-1 .
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.IR sem_nsems\-1 .
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.PP
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A semaphore is a data structure of type
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.I "struct sem"
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containing the following members:
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.sp
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.B
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int semval;
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/* semaphore value */
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.br
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.B
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int sempid;
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/* PID for last operation */
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.\".br
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.\".B
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.\" ushort semncnt;
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.\"/* nr awaiting semval to increase */
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.\".br
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.\".B
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.\" ushort semzcnt;
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.\"/* nr awaiting semval = 0 */
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.in +0.5i
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.nf
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struct sem {
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int semval; /* semaphore value */
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int sempid; /* PID for last operation */
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.\" ushort semncnt; /* nr awaiting semval to increase */
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.\" ushort semzcnt; /* nr awaiting semval = 0 */
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}
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.fi
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.in
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.TP 11
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.B semval
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.I semval
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Semaphore value: a non-negative integer.
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.TP
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.B sempid
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.I sempid
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ID of the last process that performed a semaphore operation
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on this semaphore.
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.\".TP
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.\".B semncnt
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.\".I semncnt
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.\"Number of processes suspended awaiting for
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.\".B semval
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.\".I semval
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.\"to increase.
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.\".TP
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.\".B semznt
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.\".I semznt
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.\"Number of processes suspended awaiting for
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.\".B semval
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.\".I semval
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.\"to become zero.
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.SS Shared Memory Segments
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A shared memory segment is uniquely identified by a positive integer
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@ -302,74 +269,58 @@ and has an associated data structure of type
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defined in
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.IR <sys/shm.h> ,
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containing the following members:
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.sp
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.B
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struct ipc_perm shm_perm;
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.br
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.B
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size_t shm_segsz;
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/* size of segment */
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.br
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.B
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pid_t shm_cpid;
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/* PID of creator */
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.br
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.B
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pid_t shm_lpid;
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/* PID, last operation */
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.br
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.B
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shmatt_t shm_nattch;
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/* no. of current attaches */
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.br
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.B
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time_t shm_atime;
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/* time of last attach */
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.br
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.B
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time_t shm_dtime;
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/* time of last detach */
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.br
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.B
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time_t shm_ctime;
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/* time of last change */
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.in +0.5i
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.nf
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struct shmid_ds {
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struct ipc_perm shm_perm;
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size_t shm_segsz; /* size of segment */
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pid_t shm_cpid; /* PID of creator */
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pid_t shm_lpid; /* PID, last operation */
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shmatt_t shm_nattch; /* no. of current attaches */
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time_t shm_atime; /* time of last attach */
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time_t shm_dtime; /* time of last detach */
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time_t shm_ctime; /* time of last change */
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};
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.fi
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.in
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.TP 11
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.B shm_perm
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.B ipc_perm
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.I shm_perm
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.I ipc_perm
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structure that specifies the access permissions on the shared memory
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segment.
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.TP
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.B shm_segsz
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.I shm_segsz
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Size in bytes of the shared memory segment.
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.TP
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.B shm_cpid
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.I shm_cpid
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ID of the process that created the shared memory segment.
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.TP
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.B shm_lpid
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.I shm_lpid
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ID of the last process that executed a
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.BR shmat (2)
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or
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.BR shmdt (2)
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system call.
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.TP
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.B shm_nattch
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.I shm_nattch
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Number of current alive attaches for this shared memory segment.
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.TP
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.B shm_atime
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.I shm_atime
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Time of the last
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.BR shmat (2)
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system call.
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.TP
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.B shm_dtime
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.I shm_dtime
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Time of the last
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.BR shmdt (2)
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system call.
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.TP
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.B shm_ctime
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.I shm_ctime
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Time of the last
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.BR shmctl (2)
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system call that changed
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.BR shmid_ds .
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.IR shmid_ds .
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.SH "SEE ALSO"
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.BR msgctl (2),
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.BR msgget (2),
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