Tribblix: manual page: Intro.2

INTRO(2) System Calls INTRO(2)

NAME

Intro, intro - introduction to system calls and error numbers

SYNOPSIS

#include <errno.h>

DESCRIPTION

A system call is a C library function that requests a service from
the system, such as getting the time of day. This request is
performed in the kernel. The library interface executes a trap into
the kernel, which actually executes the system call code.

Most system calls return one or more error conditions. An error
condition is indicated by an otherwise impossible return value. This
is almost always -1 or the null pointer; the individual descriptions
specify the details. An error number is also made available in the
external variable errno, which is not cleared on successful calls, so
it should be tested only after an error has been indicated.

In the case of multithreaded applications, the -mt option must be
specified on the command line at compilation time (see threads(7)).
When the -mt option is specified, errno becomes a macro that enables
each thread to have its own errno. This errno macro can be used on
either side of the assignment as though it were a variable.

An error value listed as "will fail" describes a condition whose
detection and reporting is mandatory for an implementation that
conforms to the Single UNIX Specification (SUS). An application can
rely on this condition being detected and reported. An error value
listed as "may fail" describes a condition whose detection and
reporting is optional for an implementation that conforms to the
SUS. An application should not rely this condition being detected and
reported. An application that relies on such behavior cannot be
assured to be portable across conforming implementations. If more
than one error occurs in processing a function call, any one of the
possible errors might may be returned, as the order of detection is
undefined. See standards(7) for additional information regarding the
Single UNIX Specification.

Each system call description attempts to list all possible error
numbers. The following is a complete list of the error numbers and
their names as defined in <errno.h>.

1 EPERM
Lacking appropriate privileges

Typically this error indicates an attempt to
modify a file in some way forbidden except to
its owner or an appropriately privileged
process. It is also returned for attempts by
ordinary users to perform operations allowed
only to processes with certain privileges.

The manual pages for individual functions
document which privileges are needed to
override the restriction.

2 ENOENT
No such file or directory

A file name is specified and the file should
exist but doesn't, or one of the directories
in a path name does not exist.

3 ESRCH
No such process, LWP, or thread

No process can be found in the system that
corresponds to the specified PID, LWPID_t, or
thread_t.

4 EINTR
Interrupted system call

An asynchronous signal (such as interrupt or
quit), which the user has elected to catch,
occurred during a system service function. If
execution is resumed after processing the
signal, it will appear as if the interrupted
function call returned this error condition.

In a multithreaded application, EINTR may be
returned whenever another thread or LWP calls
fork(2).

5 EIO
I/O error

Some physical I/O error has occurred. This
error may in some cases occur on a call
following the one to which it actually
applies.

6 ENXIO
No such device or address

I/O on a special file refers to a subdevice
which does not exist, or exists beyond the
limit of the device. It may also occur when,
for example, a tape drive is not on-line or no
disk pack is loaded on a drive.

7 E2BIG
Arg list too long

An argument list longer than ARG_MAX bytes is
presented to a member of the exec family of
functions (see exec(2)). The argument list
limit is the sum of the size of the argument
list plus the size of the environment's
exported shell variables.

8 ENOEXEC
Exec format error

A request is made to execute a file which,
although it has the appropriate permissions,
does not start with a valid format (see
a.out(5)).

9 EBADF
Bad file number

Either a file descriptor refers to no open
file, or a read(2) (respectively, write(2))
request is made to a file that is open only
for writing (respectively, reading).

10 ECHILD
No child processes

A wait(3C) function call was executed by a
process that had no existing or unwaited-for
child processes.

11 EAGAIN
No more processes, or no more LWPs

For example, the fork(2) function failed
because the system's process table is full or
the user is not allowed to create any more
processes, or a call failed because of
insufficient memory or swap space.

12 ENOMEM
Not enough space

During execution of brk() or sbrk() (see
brk(2)), or one of the exec family of
functions, a program asks for more space than
the system is able to supply. This is not a
temporary condition; the maximum size is a
system parameter. On some architectures, the
error may also occur if the arrangement of
text, data, and stack segments requires too
many segmentation registers, or if there is
not enough swap space during the fork(2)
function.

13 EACCES
Permission denied

An attempt was made to access a file in a way
forbidden by the protection system.

The manual pages for individual functions
document which privileges are needed to
override the protection system.

14 EFAULT
Bad address

The system encountered a hardware fault in
attempting to use an argument of a routine.
For example, errno potentially may be set to
EFAULT any time a routine that takes a pointer
argument is passed an invalid address, if the
system can detect the condition. Because
systems will differ in their ability to
reliably detect a bad address, on some
implementations passing a bad address to a
routine will result in undefined behavior.

15 ENOTBLK
Block device required

A non-block device or file was mentioned where
a block device was required (for example, in a
call to the mount(2) function).

16 EBUSY
Device busy

An attempt was made to mount a device that was
already mounted or an attempt was made to
unmount a device on which there is an active
file (open file, current directory, mounted-on
file, active text segment). It will also occur
if an attempt is made to enable accounting
when it is already enabled. The device or
resource is currently unavailable. EBUSY is
also used by mutexes, semaphores, condition
variables, and r/w locks, to indicate that a
lock is held, and by the processor control
function P_ONLINE.

17 EEXIST
File exists

An existing file was mentioned in an
inappropriate context (for example, call to
the link(2) function).

18 EXDEV
Cross-device link

A hard link to a file on another device was
attempted.

19 ENODEV
No such device

An attempt was made to apply an inappropriate
operation to a device (for example, read a
write-only device).

20 ENOTDIR
Not a directory

A non-directory was specified where a
directory is required (for example, in a path
prefix or as an argument to the chdir(2)
function).

21 EISDIR
Is a directory

An attempt was made to write on a directory.

22 EINVAL
Invalid argument

An invalid argument was specified (for
example, unmounting a non-mounted device),
mentioning an undefined signal in a call to
the signal(3C) or kill(2) function, or an
unsupported operation related to extended
attributes was attempted.

23 ENFILE
File table overflow

The system file table is full (that is,
SYS_OPEN files are open, and temporarily no
more files can be opened).

24 EMFILE
Too many open files

No process may have more than OPEN_MAX file
descriptors open at a time.

25 ENOTTY
Inappropriate ioctl for device

A call was made to the ioctl(2) function
specifying a file that is not a special
character device.

26 ETXTBSY
Text file busy (obsolete)

An attempt was made to execute a pure-
procedure program that is currently open for
writing. Also an attempt to open for writing
or to remove a pure-procedure program that is
being executed. (This message is obsolete.)

27 EFBIG
File too large

The size of the file exceeded the limit
specified by resource RLIMIT_FSIZEn; the file
size exceeds the maximum supported by the file
system; or the file size exceeds the offset
maximum of the file descriptor. See the File
Descriptor subsection of the DEFINITIONS
section below.

28 ENOSPC
No space left on device

While writing an ordinary file or creating a
directory entry, there is no free space left
on the device. In the fcntl(2) function, the
setting or removing of record locks on a file
cannot be accomplished because there are no
more record entries left on the system.

29 ESPIPE
Illegal seek

A call to the lseek(2) function was issued to
a pipe.

30 EROFS
Read-only file system

An attempt to modify a file or directory was
made on a device mounted read-only.

31 EMLINK
Too many links

An attempt to make more than the maximum
number of links, LINK_MAX, to a file.

32 EPIPE
Broken pipe

A write on a pipe for which there is no
process to read the data. This condition
normally generates a signal; the error is
returned if the signal is ignored.

33 EDOM
Math argument out of domain of function

The argument of a function in the math package
(3M) is out of the domain of the function.

34 ERANGE
Math result not representable

The value of a function in the math package
(3M) is not representable within machine
precision.

35 ENOMSG
No message of desired type

An attempt was made to receive a message of a
type that does not exist on the specified
message queue (see msgrcv(2)).

36 EIDRM
Identifier removed

This error is returned to processes that
resume execution due to the removal of an
identifier from the file system's name space
(see msgctl(2), semctl(2), and shmctl(2)).

37 ECHRNG
Channel number out of range

38 EL2NSYNC
Level 2 not synchronized

39 EL3HLT
Level 3 halted

40 EL3RST
Level 3 reset

41 ELNRNG
Link number out of range

42 EUNATCH
Protocol driver not attached

43 ENOCSI
No CSI structure available

44 EL2HLT
Level 2 halted

45 EDEADLK
Deadlock condition

A deadlock situation was detected and avoided.
This error pertains to file and record
locking, and also applies to mutexes,
semaphores, condition variables, and r/w
locks.

46 ENOLCK
No record locks available

There are no more locks available. The system
lock table is full (see fcntl(2)).

47 ECANCELED
Operation canceled

The associated asynchronous operation was
canceled before completion.

48 ENOTSUP
Not supported

This version of the system does not support
this feature. Future versions of the system
may provide support.

49 EDQUOT
Disc quota exceeded

A write(2) to an ordinary file, the creation
of a directory or symbolic link, or the
creation of a directory entry failed because
the user's quota of disk blocks was exhausted,
or the allocation of an inode for a newly
created file failed because the user's quota
of inodes was exhausted.

58-59
Reserved

60 ENOSTR
Device not a stream

A putmsg(2) or getmsg(2) call was attempted on
a file descriptor that is not a STREAMS
device.

61 ENODATA
No data available

62 ETIME
Timer expired

The timer set for a STREAMS ioctl(2) call has
expired. The cause of this error is device-
specific and could indicate either a hardware
or software failure, or perhaps a timeout
value that is too short for the specific
operation. The status of the ioctl() operation
is indeterminate. This is also returned in the
case of _lwp_cond_timedwait(2) or
cond_timedwait(3C).

63 ENOSR
Out of stream resources

During a STREAMS open(2) call, either no
STREAMS queues or no STREAMS head data
structures were available. This is a temporary
condition; one may recover from it if other
processes release resources.

65 ENOPKG
Package not installed

This error occurs when users attempt to use a
call from a package which has not been
installed.

71 EPROTO
Protocol error

Some protocol error occurred. This error is
device-specific, but is generally not related
to a hardware failure.

77 EBADMSG
Not a data message

During a read(2), getmsg(2), or ioctl(2)
I_RECVFD call to a STREAMS device, something
has come to the head of the queue that can not
be processed. That something depends on the
call:

read():
control information or passed
file descriptor.

getmsg():
passed file descriptor.

ioctl():
control or data information.

78 ENAMETOOLONG
File name too long

The length of the path argument exceeds
PATH_MAX, or the length of a path component
exceeds NAME_MAX while _POSIX_NO_TRUNC is in
effect; see limits.h(3HEAD).

79 EOVERFLOW
Value too large for defined data type.

80 ENOTUNIQ
Name not unique on network

Given log name not unique.

81 EBADFD
File descriptor in bad state

Either a file descriptor refers to no open
file or a read request was made to a file that
is open only for writing.

82 EREMCHG
Remote address changed

83 ELIBACC
Cannot access a needed share library

Trying to exec an a.out that requires a static
shared library and the static shared library
does not exist or the user does not have
permission to use it.

84 ELIBBAD
Accessing a corrupted shared library

Trying to exec an a.out that requires a static
shared library (to be linked in) and exec
could not load the static shared library. The
static shared library is probably corrupted.

85 ELIBSCN
.lib section in a.out corrupted

Trying to exec an a.out that requires a static
shared library (to be linked in) and there was
erroneous data in the .lib section of the
a.out. The .lib section tells exec what static
shared libraries are needed. The a.out is
probably corrupted.

86 ELIBMAX
Attempting to link in more shared libraries
than system limit

Trying to exec an a.out that requires more
static shared libraries than is allowed on the
current configuration of the system. See
System Administration Guide: IP Services

87 ELIBEXEC
Cannot exec a shared library directly

Attempting to exec a shared library directly.

88 EILSEQ
Error 88

Illegal byte sequence. Handle multiple
characters as a single character.

89 ENOSYS
Operation not applicable

90 ELOOP
Number of symbolic links encountered during
path name traversal exceeds MAXSYMLINKS

91 ESTART
Restartable system call

Interrupted system call should be restarted.

92 ESTRPIPE
If pipe/FIFO, don't sleep in stream head

Streams pipe error (not externally visible).

93 ENOTEMPTY
Directory not empty

94 EUSERS
Too many users

95 ENOTSOCK
Socket operation on non-socket

96 EDESTADDRREQ
Destination address required

A required address was omitted from an
operation on a transport endpoint.
Destination address required.

97 EMGSIZE
Message too long

A message sent on a transport provider was
larger than the internal message buffer or
some other network limit.

98 EPROTOTYPE
Protocol wrong type for socket

A protocol was specified that does not support
the semantics of the socket type requested.

99 ENOPROTOOPT
Protocol not available

A bad option or level was specified when
getting or setting options for a protocol.

120 EPROTONOSUPPORT
Protocol not supported

The protocol has not been configured into the
system or no implementation for it exists.

121 ESOCKTNOSUPPORT
Socket type not supported

The support for the socket type has not been
configured into the system or no
implementation for it exists.

122 EOPNOTSUPP
Operation not supported on transport endpoint

For example, trying to accept a connection on
a datagram transport endpoint.

123 EPFNOSUPPORT
Protocol family not supported

The protocol family has not been configured
into the system or no implementation for it
exists. Used for the Internet protocols.

124 EAFNOSUPPORT
Address family not supported by protocol
family

An address incompatible with the requested
protocol was used.

125 EADDRINUSE
Address already in use

User attempted to use an address already in
use, and the protocol does not allow this.

126 EADDRNOTAVAIL
Cannot assign requested address

Results from an attempt to create a transport
endpoint with an address not on the current
machine.

127 ENETDOWN
Network is down

Operation encountered a dead network.

128 ENETUNREACH
Network is unreachable

Operation was attempted to an unreachable
network.

129 ENETRESET
Network dropped connection because of reset

The host you were connected to crashed and
rebooted.

130 ECONNABORTED
Software caused connection abort

A connection abort was caused internal to your
host machine.

131 ECONNRESET
Connection reset by peer

A connection was forcibly closed by a peer.
This normally results from a loss of the
connection on the remote host due to a timeout
or a reboot.

132 ENOBUFS
No buffer space available

An operation on a transport endpoint or pipe
was not performed because the system lacked
sufficient buffer space or because a queue was
full.

133 EISCONN
Transport endpoint is already connected

A connect request was made on an already
connected transport endpoint; or, a
sendto(3SOCKET) or sendmsg(3SOCKET) request on
a connected transport endpoint specified a
destination when already connected.

134 ENOTCONN
Transport endpoint is not connected

A request to send or receive data was
disallowed because the transport endpoint is
not connected and (when sending a datagram) no
address was supplied.

143 ESHUTDOWN
Cannot send after transport endpoint shutdown

A request to send data was disallowed because
the transport endpoint has already been shut
down.

144 ETOOMANYREFS
Too many references: cannot splice

145 ETIMEDOUT
Connection timed out

A connect(3SOCKET) or send(3SOCKET) request
failed because the connected party did not
properly respond after a period of time; or a
write(2) or fsync(3C) request failed because
a file is on an NFS file system mounted with
the soft option.

146 ECONNREFUSED
Connection refused

No connection could be made because the target
machine actively refused it. This usually
results from trying to connect to a service
that is inactive on the remote host.

147 EHOSTDOWN
Host is down

A transport provider operation failed because
the destination host was down.

148 EHOSTUNREACH
No route to host

A transport provider operation was attempted
to an unreachable host.

149 EALREADY
Operation already in progress

An operation was attempted on a non-blocking
object that already had an operation in
progress.

150 EINPROGRESS
Operation now in progress

An operation that takes a long time to
complete (such as a connect()) was attempted
on a non-blocking object.

151 ESTALE
Stale NFS file handle

DEFINITIONS

Background Process Group

Any process group that is not the foreground process group of a
session that has established a connection with a controlling
terminal.

Controlling Process

A session leader that established a connection to a controlling
terminal.

Controlling Terminal

A terminal that is associated with a session. Each session may have,
at most, one controlling terminal associated with it and a
controlling terminal may be associated with only one session.
Certain input sequences from the controlling terminal cause signals
to be sent to process groups in the session associated with the
controlling terminal; see termio(4I).

Downstream

In a stream, the direction from stream head to driver.

Driver

In a stream, the driver provides the interface between peripheral
hardware and the stream. A driver can also be a pseudo-driver, such
as a multiplexor or log driver (see log(4D)), which is not associated
with a hardware device.

Effective User ID and Effective Group ID
An active process has an effective user ID and an effective group ID
that are used to determine file access permissions (see below). The
effective user ID and effective group ID are equal to the process's
real user ID and real group ID, respectively, unless the process or
one of its ancestors evolved from a file that had the set-user-ID
bit or set-group-ID bit set (see exec(2)).

File Access Permissions

Read, write, and execute/search permissions for a file are granted to
a process if one or more of the following are true:

o The effective user ID of the process matches the user ID
of the owner of the file and the appropriate access bit of
the "owner" portion (0700) of the file mode is set.

o The effective user ID of the process does not match the
user ID of the owner of the file, but either the effective
group ID or one of the supplementary group IDs of the
process match the group ID of the file and the
appropriate access bit of the "group" portion (0070) of
the file mode is set.

o The effective user ID of the process does not match the
user ID of the owner of the file, and neither the
effective group ID nor any of the supplementary group IDs
of the process match the group ID of the file, but the
appropriate access bit of the "other" portion (0007) of
the file mode is set.

o The read, write, or execute mode bit is not set but the
process has the discretionary file access override
privilege for the corresponding mode bit:
{PRIV_FILE_DAC_READ} for the read bit
{PRIV_FILE_DAC_WRITE} for the write bit,
{PRIV_FILE_DAC_SEARCH} for the execute bit on directories,
and {PRIV_FILE_DAC_EXECUTE} for the executable bit on
plain files.

Otherwise, the corresponding permissions are denied.

File Descriptor

A file descriptor is a small integer used to perform I/O on a file.
The value of a file descriptor is from 0 to (NOFILES-1). A process
may have no more than NOFILES file descriptors open simultaneously.
A file descriptor is returned by calls such as open(2) or pipe(2).
The file descriptor is used as an argument by calls such as read(2),
write(2), ioctl(2), and close(2).

Each file descriptor has a corresponding offset maximum. For regular
files that were opened without setting the O_LARGEFILE flag, the
offset maximum is 2 Gbyte - 1 byte (2^31 -1 bytes). For regular files
that were opened with the O_LARGEFILE flag set, the offset maximum is
2^63 -1 bytes.

File Name

Names consisting of 1 to NAME_MAX characters may be used to name an
ordinary file, special file or directory.

These characters may be selected from the set of all character values
excluding \0 (null) and the ASCII code for / (slash).

Note that it is generally unwise to use *, ?, [, or ] as part of file
names because of the special meaning attached to these characters by
the shell (see sh(1), csh(1), and ksh(1)). Although permitted, the
use of unprintable characters in file names should be avoided.

A file name is sometimes referred to as a pathname component. The
interpretation of a pathname component is dependent on the values of
NAME_MAX and _POSIX_NO_TRUNC associated with the path prefix of that
component. If any pathname component is longer than NAME_MAX and
_POSIX_NO_TRUNC is in effect for the path prefix of that component
(see fpathconf(2) and limits.h(3HEAD)), it shall be considered an
error condition in that implementation. Otherwise, the
implementation shall use the first NAME_MAX bytes of the pathname
component.

Foreground Process Group

Each session that has established a connection with a controlling
terminal will distinguish one process group of the session as the
foreground process group of the controlling terminal. This group has
certain privileges when accessing its controlling terminal that are
denied to background process groups.

{IOV_MAX}
Maximum number of entries in a struct iovec array.

{LIMIT}
The braces notation, {LIMIT}, is used to denote a magnitude
limitation imposed by the implementation. This indicates a value
which may be defined by a header file (without the braces), or the
actual value may be obtained at runtime by a call to the
configuration inquiry pathconf(2) with the name argument _PC_LIMIT.

Masks

The file mode creation mask of the process used during any create
function calls to turn off permission bits in the mode argument
supplied. Bit positions that are set in umask(cmask) are cleared in
the mode of the created file.

Message

In a stream, one or more blocks of data or information, with
associated STREAMS control structures. Messages can be of several
defined types, which identify the message contents. Messages are the
only means of transferring data and communicating within a stream.

Message Queue

In a stream, a linked list of messages awaiting processing by a
module or driver.

Message Queue Identifier

A message queue identifier (msqid) is a unique positive integer
created by a msgget(2) call. Each msqid has a message queue and a
data structure associated with it. The data structure is referred to
as msqid_ds and contains the following members:

struct ipc_perm msg_perm;
struct msg *msg_first;
struct msg *msg_last;
ulong_t msg_cbytes;
ulong_t msg_qnum;
ulong_t msg_qbytes;
pid_t msg_lspid;
pid_t msg_lrpid;
time_t msg_stime;
time_t msg_rtime;
time_t msg_ctime;

The following are descriptions of the msqid_ds structure members:

The msg_perm member is an ipc_perm structure that specifies the
message 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/w permission */
ulong_t seq; /* slot usage sequence # */
key_t key; /* key */

The *msg_first member is a pointer to the first message on the queue.

The *msg_last member is a pointer to the last message on the queue.

The msg_cbytes member is the current number of bytes on the queue.

The msg_qnum member is the number of messages currently on the queue.

The msg_qbytes member is the maximum number of bytes allowed on the
queue.

The msg_lspid member is the process ID of the last process that
performed a msgsnd() operation.

The msg_lrpid member is the process id of the last process that
performed a msgrcv() operation.

The msg_stime member is the time of the last msgsnd() operation.

The msg_rtime member is the time of the last msgrcv() operation.

The msg_ctime member is the time of the last msgctl() operation that
changed a member of the above structure.

Message Operation Permissions

In the msgctl(2), msgget(2), msgrcv(2), and msgsnd(2) function
descriptions, the permission required for an operation is given as
{token}, where token is the type of permission needed, interpreted as
follows:

00400 READ by user
00200 WRITE by user
00040 READ by group
00020 WRITE by group
00004 READ by others
00002 WRITE by others

Read and write permissions for a msqid are granted to a process if
one or more of the following are true:

o The {PRIV_IPC_DAC_READ} or {PRIV_IPC_DAC_WRITE} privilege
is present in the effective set.

o The effective user ID of the process matches msg_perm.cuid
or msg_perm.uid in the data structure associated with
msqid and the appropriate bit of the "user" portion (0600)
of msg_perm.mode is set.

o Any group ID in the process credentials from the set
(cr_gid, cr_groups) matches msg_perm.cgid or msg_perm.gid
and the appropriate bit of the "group" portion (060) of
msg_perm.mode is set.

o The appropriate bit of the "other" portion (006) of
msg_perm.mode is set."

Otherwise, the corresponding permissions are denied.

Module

A module is an entity containing processing routines for input and
output data. It always exists in the middle of a stream, between the
stream's head and a driver. A module is the STREAMS counterpart to
the commands in a shell pipeline except that a module contains a pair
of functions which allow independent bidirectional (downstream and
upstream) data flow and processing.

Multiplexor

A multiplexor is a driver that allows streams associated with several
user processes to be connected to a single driver, or several drivers
to be connected to a single user process. STREAMS does not provide a
general multiplexing driver, but does provide the facilities for
constructing them and for connecting multiplexed configurations of
streams.

Offset Maximum

An offset maximum is an attribute of an open file description
representing the largest value that can be used as a file offset.

Orphaned Process Group

A process group in which the parent of every member in the group is
either itself a member of the group, or is not a member of the
process group's session.

Path Name

A path name is a null-terminated character string starting with an
optional slash (/), followed by zero or more directory names
separated by slashes, optionally followed by a file name.

If a path name begins with a slash, the path search begins at the
root directory. Otherwise, the search begins from the current working
directory.

A slash by itself names the root directory.

Unless specifically stated otherwise, the null path name is treated
as if it named a non-existent file.

Privileged User

Solaris software implements a set of privileges that provide fine-
grained control over the actions of processes. The possession of of a
certain privilege allows a process to perform a specific set of
restricted operations. Prior to the Solaris 10 release, a process
running with uid 0 was granted all privileges. See privileges(7) for
the semantics and the degree of backward compatibility awarded to
processes with an effective uid of 0.

Process ID

Each process in the system is uniquely identified during its lifetime
by a positive integer called a process ID. A process ID cannot be
reused by the system until the process lifetime, process group
lifetime, and session lifetime ends for any process ID, process group
ID, and session ID equal to that process ID. There are threads within
a process with thread IDs thread_t and LWPID_t. These threads are not
visible to the outside process.

Parent Process ID

A new process is created by a currently active process (see fork(2)).
The parent process ID of a process is the process ID of its creator.

Privilege

Having appropriate privilege means having the capability to override
system restrictions.

Process Group

Each process in the system is a member of a process group that is
identified by a process group ID. Any process that is not a process
group leader may create a new process group and become its leader.
Any process that is not a process group leader may join an existing
process group that shares the same session as the process. A newly
created process joins the process group of its parent.

Process Group Leader

A process group leader is a process whose process ID is the same as
its process group ID.

Process Group ID

Each active process is a member of a process group and is identified
by a positive integer called the process group ID. This ID is the
process ID of the group leader. This grouping permits the signaling
of related processes (see kill(2)).

Process Lifetime

A process lifetime begins when the process is forked and ends after
it exits, when its termination has been acknowledged by its parent
process. See wait(3C).

Process Group Lifetime

A process group lifetime begins when the process group is created by
its process group leader, and ends when the lifetime of the last
process in the group ends or when the last process in the group
leaves the group.

Processor Set ID

The processors in a system may be divided into subsets, known as
processor sets. A process bound to one of these sets will run only on
processors in that set, and the processors in the set will normally
run only processes that have been bound to the set. Each active
processor set is identified by a positive integer. See
pset_create(2).

Read Queue

In a stream, the message queue in a module or driver containing
messages moving upstream.

Real User ID and Real Group ID
Each user allowed on the system is identified by a positive integer
(0 to MAXUID) called a real user ID.

Each user is also a member of a group. The group is identified by a
positive integer called the real group ID.

An active process has a real user ID and real group ID that are set
to the real user ID and real group ID, respectively, of the user
responsible for the creation of the process.

Root Directory and Current Working Directory

Each process has associated with it a concept of a root directory and
a current working directory for the purpose of resolving path name
searches. The root directory of a process need not be the root
directory of the root file system.

Saved Resource Limits

Saved resource limits is an attribute of a process that provides some
flexibility in the handling of unrepresentable resource limits, as
described in the exec family of functions and setrlimit(2).

Saved User ID and Saved Group ID
The saved user ID and saved group ID are the values of the effective
user ID and effective group ID just after an exec of a file whose set
user or set group file mode bit has been set (see exec(2)).

Semaphore Identifier

A semaphore identifier (semid) is a unique positive integer created
by a semget(2) 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 following members:

struct ipc_perm sem_perm; /* operation permission struct */
struct sem *sem_base; /* ptr to first semaphore in set */
ushort_t 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 */

The following are descriptions of the semid_ds structure members:

The sem_perm member is an ipc_perm structure that specifies the
semaphore operation permission (see below). This structure includes
the following members:

uid_t uid; /* user id */
gid_t gid; /* group id */
uid_t cuid; /* creator user id */
gid_t cgid; /* creator group id */
mode_t mode; /* r/a permission */
ulong_t seq; /* slot usage sequence number */
key_t key; /* key */

The sem_nsems member is equal to the number of semaphores in the set.
Each semaphore in the set is referenced by a nonnegative integer
referred to as a sem_num. sem_num values run sequentially from 0 to
the value of sem_nsems minus 1.

The sem_otime member is the time of the last semop(2) operation.

The sem_ctime member is the time of the last semctl(2) operation that
changed a member of the above structure.

A semaphore is a data structure called sem that contains the
following members:

ushort_t semval; /* semaphore value */
pid_t sempid; /* pid of last operation */
ushort_t semncnt; /* # awaiting semval > cval */
ushort_t semzcnt; /* # awaiting semval = 0 */

The following are descriptions of the sem structure members:

The semval member is a non-negative integer that is the actual value
of the semaphore.

The sempid member is equal to the process ID of the last process that
performed a semaphore operation on this semaphore.

The semncnt member is a count of the number of processes that are
currently suspended awaiting this semaphore's semval to become
greater than its current value.

The semzcnt member is a count of the number of processes that are
currently suspended awaiting this semaphore's semval to become 0.

Semaphore Operation Permissions

In the semop(2) and semctl(2) function descriptions, the permission
required for an operation is given as {token}, where token is the
type of permission needed interpreted as follows:

00400 READ by user
00200 ALTER by user
00040 READ by group
00020 ALTER by group
00004 READ by others
00002 ALTER by others

Read and alter permissions for a semid are granted to a process if
one or more of the following are true:

o The {PRIV_IPC_DAC_READ} or {PRIV_IPC_DAC_WRITE} privilege
is present in the effective set.

o The effective user ID of the process matches sem_perm.cuid
or sem_perm.uid in the data structure associated with
semid and the appropriate bit of the "user" portion (0600)
of sem_perm.mode is set.

o The effective group ID of the process matches
sem_perm.cgid or sem_perm.gid and the appropriate bit of
the "group" portion (060) of sem_perm.mode is set.

o The appropriate bit of the "other" portion (06) of
sem_perm.mode is set.

Otherwise, the corresponding permissions are denied.

Session

A session is a group of processes identified by a common ID called a
session ID, capable of establishing a connection with a controlling
terminal. Any process that is not a process group leader may create
a new session and process group, becoming the session leader of the
session and process group leader of the process group. A newly
created process joins the session of its creator.

Session ID

Each session in the system is uniquely identified during its lifetime
by a positive integer called a session ID, the process ID of its
session leader.

Session Leader

A session leader is a process whose session ID is the same as its
process and process group ID.

Session Lifetime

A session lifetime begins when the session is created by its session
leader, and ends when the lifetime of the last process that is a
member of the session ends, or when the last process that is a
member in the session leaves the session.

Shared Memory Identifier

A shared memory identifier (shmid) is a unique positive integer
created by a shmget(2) call. Each shmid has a segment of memory
(referred to as a shared memory segment) and a data structure
associated with it. (Note that these shared memory segments must be
explicitly removed by the user after the last reference to them is
removed.) The data structure is referred to as shmid_ds and contains
the following members:

struct ipc_perm shm_perm; /* operation permission struct */
size_t shm_segsz; /* size of segment */
struct anon_map *shm_amp; /* ptr to region structure */
char pad[4]; /* for swap compatibility */
pid_t shm_lpid; /* pid of last operation */
pid_t shm_cpid; /* creator pid */
shmatt_t shm_nattch; /* number of current attaches */
ulong_t shm_cnattch; /* used only for shminfo */
time_t shm_atime; /* last attach time */
time_t shm_dtime; /* last detach time */
time_t shm_ctime; /* last change time */
/* Times measured in secs since */
/* 00:00:00 GMT, Jan. 1, 1970 */

The following are descriptions of the shmid_ds structure members:

The shm_perm member is an ipc_perm structure that specifies the
shared memory 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/w permission */
ulong_t seq; /* slot usage sequence # */
key_t key; /* key */

The shm_segsz member specifies the size of the shared memory segment
in bytes.

The shm_cpid member is the process ID of the process that created the
shared memory identifier.

The shm_lpid member is the process ID of the last process that
performed a shmat() or shmdt() operation (see shmop(2)).

The shm_nattch member is the number of processes that currently have
this segment attached.

The shm_atime member is the time of the last shmat() operation (see
shmop(2)).

The shm_dtime member is the time of the last shmdt() operation (see
shmop(2)).

The shm_ctime member is the time of the last shmctl(2) operation that
changed one of the members of the above structure.

Shared Memory Operation Permissions

In the shmctl(2), shmat(), and shmdt() (see shmop(2)) function
descriptions, the permission required for an operation is given as
{token}, where token is the type of permission needed interpreted as
follows:

00400 READ by user
00200 WRITE by user
00040 READ by group
00020 WRITE by group
00004 READ by others
00002 WRITE by others

Read and write permissions for a shmid are granted to a process if
one or more of the following are true:

o The {PRIV_IPC_DAC_READ} or {PRIV_IPC_DAC_WRITE} privilege
is present in the effective set.

o The effective user ID of the process matches shm_perm.cuid
or shm_perm.uid in the data structure associated with
shmid and the appropriate bit of the "user" portion (0600)
of shm_perm.mode is set.

o The effective group ID of the process matches
shm_perm.cgid or shm_perm.gid and the appropriate bit of
the "group" portion (060) of shm_perm.mode is set.

o The appropriate bit of the "other" portion (06) of
shm_perm.mode is set.

Otherwise, the corresponding permissions are denied.

Special Processes

The process with ID 0 and the process with ID 1 are special processes
referred to as proc0 and proc1; see kill(2). proc0 is the process
scheduler. proc1 is the initialization process (init); proc1 is the
ancestor of every other process in the system and is used to control
the process structure.

STREAMS

A set of kernel mechanisms that support the development of network
services and data communication drivers. It defines interface
standards for character input/output within the kernel and between
the kernel and user level processes. The STREAMS mechanism is
composed of utility routines, kernel facilities and a set of data
structures.

Stream

A stream is a full-duplex data path within the kernel between a user
process and driver routines. The primary components are a stream
head, a driver, and zero or more modules between the stream head and
driver. A stream is analogous to a shell pipeline, except that data
flow and processing are bidirectional.

Stream Head

In a stream, the stream head is the end of the stream that provides
the interface between the stream and a user process. The principal
functions of the stream head are processing STREAMS-related system
calls and passing data and information between a user process and the
stream.

Upstream

In a stream, the direction from driver to stream head.

Write Queue

In a stream, the message queue in a module or driver containing
messages moving downstream.

ACKNOWLEDGMENTS

Sun Microsystems, Inc. gratefully acknowledges The Open Group for
permission to reproduce portions of its copyrighted documentation.
Original documentation from The Open Group can be obtained online at
http://www.opengroup.org/bookstore/.

The Institute of Electrical and Electronics Engineers and The Open
Group, have given us permission to reprint portions of their
documentation.

In the following statement, the phrase ``this text'' refers to
portions of the system documentation.

Portions of this text are reprinted and reproduced in electronic form
in the SunOS Reference Manual, from IEEE Std 1003.1, 2004 Edition,
Standard for Information Technology -- Portable Operating System
Interface (POSIX), The Open Group Base Specifications Issue 6,
Copyright (C) 2001-2004 by the Institute of Electrical and
Electronics Engineers, Inc and The Open Group. In the event of any
discrepancy between these versions and the original IEEE and The Open
Group Standard, the original IEEE and The Open Group Standard is the
referee document. The original Standard can be obtained online at
http://www.opengroup.org/unix/online.html.

This notice shall appear on any product containing this material.