HP-UX Reference (11i v3 07/02) - 7 Device (Special) Files, 9 General Information, Index (vol 10)

s
glossary(9) glossary(9)
enter a shell programming language control-flow construct (such as a
for construct) from the command
line. By default, the shell’s secondary prompt is the greater-than sign (
>), but you can re-define it by set-
ting the shell variable
PS2 appropriately in your
.profile file. (The C shell has no secondary prompt.)
semaphore identifier (semid)
A unique positive integer created by a semget(2) system call. Each semid has a set of semaphores and a
data structure associated with it. The data structure is referred to as
semid_ds and contains the follow-
ing members:
struct
ipc_perm sem_perm; /* operation permission */
ushort sem_nsems; /* number of sems in set */
time_t sem_otime; /* last operation time */
time_t sem_ctime; /* last change time */
/* Times measured in secs since */
/* 00:00:00 GMT, Jan. 1, 1970 */
Semaphore identifiers can be created using ftok(3C).
sem_perm is a ipc_perm structure that specifies the semaphore operation permission (see below). This
structure includes the following members:
uid_t cuid; /* creator user id */
gid_t cgid; /* creator group id */
uid_t uid; /* user id */
gid_t gid; /* group id */
mode_t mode; /* r/a permission */
The value of sem_nsems is equal to the number of semaphores in the set. Each semaphore in the set is
referenced by a positive integer referred to as a sem_num. sem_num values run sequentially from 0 to
the value of sem_nsems minus 1. sem_otime is the time of the last semop(2) operation, and
sem_ctime is the time of the last semctl(2) operation that changed a member of the above structure.
semaphore operation permissions
In the semop(2) and semctl(2) system call descriptions, the permission required for an operation is indicated
for each operation. Whether a particular process has these permissions for an object is determined by the
object’s permission mode bits as follows:
00400 Read by user
00200 Alter by user
00060 Read, Alter by group
00006 Read, Alter by others
Read and Alter permissions on a semid are granted to a process if one or more of the following are true:
• The process’s effective user ID is superuser.
• The process’s effective user ID matches
sem_perm.[c]uid in the data structure associated with
semid and the appropriate bit of the "user" portion (0600) of
sem_perm.mode
is set.
• The process’s effective user ID does not match
sem_perm.[c]uid and the appropriate bit of the
"group" portion (060) of sem_perm.mode is set.
• The process’s effective user ID does not match sem_perm. [c]uid and the process’s effective group
ID does not match sem_perm. [c]gid and neither of sem_perm.[c]gid is in the process’s group
access list and the appropriate bit of the "other" portion (06) of sem_perm.mode is set.
Otherwise, the corresponding permissions are denied.
semid
See semaphore identifier.
session
Each process group is a member of a session. A process is considered to be a member of the session of
which its process group is a member. A newly created process joins the session of its creator. A process
can alter its session membership (see setsid(2)). A session can have multiple process groups (see
setpgid(2)).
HP-UX 11i Version 3: February 2007 − 20 − Hewlett-Packard Company 265