System Calls Intro(2)
NAME
Intro, intro - introduction to system calls and error
numbers
SYNOPSIS
#include <errno.h>
DESCRIPTION
This section describes all of the system calls. Most of
these calls have one or more error returns. An error condi-
tion is indicated by an otherwise impossible returned 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. errno 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 _REENTRANT
flag must be defined on the command line at compilation time
(-D_REENTRANT). When the _REENTRANT flag is defined, errno
becomes a macro which enables each thread to have its own
errno. This errno macro can be used on either side of the
assignment , just as if it were a variable.
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 Not super-user
Typically this error indicates an attempt to modify a
file in some way forbidden except to its owner or the
super-user. It is also returned for attempts by ordi-
nary users to do things allowed only to the super-user.
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 routine. If execution is resumed after
processing the signal, it will appear as if the inter-
rupted routine call returned this error condition.
In a multi-threaded application, EINTR may be
returned whenever another thread or LWP calls
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System Calls Intro(2)
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 routines.
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(4)).
9 EBADF Bad file number
Either a file descriptor refers to no open file, or a
read (respectively, write) request is made to a file
that is open only for writing (respectively, read-
ing).
10 ECHILD No child processes
A wait routine 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 routine failed because the
system's process table is full or the user is not
allowed to create any more processes, or a system
call failed because of insufficient memory or swap
space.
12 ENOMEM Not enough space
During execution of an exec, brk, or sbrk routine, 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 archi-
tectures, 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 routine. If this error
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occurs on a resource associated with Remote File
Sharing (RFS), it indicates a memory depletion which
may be temporary, dependent on system activity at the
time the call was invoked.
13 EACCES Permission denied
An attempt was made to access a file in a way forbid-
den by 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 reli-
ably 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 routine).
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 seg-
ment). 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 vari-
ables, and r/w locks, to indicate that a lock is
held. And, EBUSY is also used by the processor con-
trol function P_ONLINE.
17 EEXIST File exists
An existing file was mentioned in an inappropriate
context (for example, call to the link routine).
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 opera-
tion to a device (for example, read a write-only dev-
ice).
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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 routine).
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 unde-
fined signal in a call to the signal or kill routine.
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 descrip-
tors open at a time.
25 ENOTTY Inappropriate ioctl for device
A call was made to the ioctl routine 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 pro-
gram 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 mes-
sage is obsolete.)
27 EFBIG File too large
The size of the file exceeded the limit specified by
resource RLIMIT_FSIZE; or, the file size exceeds the
maximum supported by the file system.
28 ENOSPC No space left on device
While writing an ordinary file or creating a direc-
tory entry, there is no free space left on the dev-
ice. In the fcntl routine, 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 routine 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.
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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 func
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 msgop(2)).
36 EIDRM Identifier removed
This error is returned to processes that resume exe-
cution 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.
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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() 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 or getmsg system 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 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 opera-
tion is indeterminate. This is also returned in the
case of _lwp_cond_timedwait() or cond_timedwait().
63 ENOSR Out of stream resources
During a STREAMS open, 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.
64 ENONET Machine is not on the network
This error is Remote File Sharing (RFS) specific. It
occurs when users try to advertise, unadvertise,
mount, or unmount remote resources while the machine
has not done the proper startup to connect to the
network.
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65 ENOPKG Package not installed
This error occurs when users attempt to use a system
call from a package which has not been installed.
66 EREMOTE Object is remote
This error is RFS specific. It occurs when users try
to advertise a resource which is not on the local
machine, or try to mount/unmount a device (or path-
name) that is on a remote machine.
67 ENOLINK Link has been severed
This error is RFS specific. It occurs when the link
(virtual circuit) connecting to a remote machine is
gone.
68 EADV Advertise error
This error is RFS specific. It occurs when users try
to advertise a resource which has been advertised
already, or try to stop RFS while there are resources
still advertised, or try to force unmount a resource
when it is still advertised.
69 ESRMNT Srmount error
This error is RFS specific. It occurs when an
attempt is made to stop RFS while resources are still
mounted by remote machines, or when a resource is
readvertised with a client list that does not include
a remote machine that currently has the resource
mounted.
70 ECOMM Communication error on send
This error is RFS specific. It occurs when the
current process is waiting for a message from a
remote machine, and the virtual circuit fails.
71 EPROTO Protocol error
Some protocol error occurred. This error is device
specific, but is generally not related to a hardware
failure.
74 EMULTIHOP Multihop attempted
This error is RFS specific. It occurs when users try
to access remote resources which are not directly
accessible.
76 EDOTDOT Error 76
This error is RFS specific. A way for the server to
tell the client that a process has transferred back
from mount point.
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77 EBADMSG Not a data message
During a read, getmsg, or ioctl I_RECVFD system call
to a STREAMS device, something has come to the head
of the queue that can't be processed. That something
depends on the system call:
read: control information or passed file descrip-
tor.
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(4).
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 shared library
Trying to exec an a.out that requires a static shared
library and the static shared library doesn't exist
or the user doesn't 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 sec-
tion 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 con-
figuration of the system. See NFS Administration
Guide.
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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 EMSGSIZE Message too long
A message sent on a transport provider was larger
than the internal message buffer or some other net-
work 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 config-
ured into the system or no implementation for it
exists.
122 EOPNOTSUPP Operation not supported on transport end-
point
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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 end-
point 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 or sendmsg request
on a connected transport endpoint specified a desti-
nation when already connected.
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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 shut-
down
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 or send request failed because the con-
nected party did not properly respond after a period
of time. (The timeout period is dependent on the
communication protocol.)
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 con-
trolling terminal.
Controlling Process
A session leader that established a connection to a control-
ling terminal.
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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(7I).
Directory
Directories organize files into a hierarchical system where
directories are the nodes in the hierarchy. A directory is
a file that catalogues the list of files, including direc-
tories (sub-directories), that are directly beneath it in
the hierarchy. Entries in a directory file are called
links. A link associates a file identifier with a filename.
By convention, a directory contains at least two links, .
(dot) and .. (dot-dot). The link called dot refers to the
directory itself while dot-dot refers to its parent direc-
tory. The root directory, which is the top-most node of the
hierarchy, has itself as its parent directory. The pathname
of the root directory is / and the parent directory of the
root directory is /.
Downstream
In a stream, the direction from stream head to driver.
Driver
In a stream, the driver provides the interface between peri-
pheral hardware and the stream. A driver can also be a
pseudo-driver, such as a multiplexor or log driver (see
log(7D)), 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 on a file are
granted to a process if one or more of the following are
true:
The effective user ID of the process is super-user.
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
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set.
The effective user ID of the process does not match the
user ID of the owner of the file, but either the effec-
tive 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.
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.
Otherwise, the corresponding permissions are denied.
File Descriptor
A file descriptor is a small integer used to do 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 system calls such as open, or pipe. The file
descriptor is used as an argument by calls such as read,
write, ioctl, and close.
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 charac-
ter 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 charac-
ters in file names should be avoided.
A file name is sometimes referred to as a pathname com-
ponent. 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(4)), it shall be con-
sidered an error condition in that implementation. Other-
wise, the implementation shall use the first NAME_MAX bytes
of the pathname component.
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Foreground Process Group
Each session that has established a connection with a con-
trolling 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 pro-
cess 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 commun-
icating 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 system 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 msg_cbytes;
ulong msg_qnum;
ulong msg_qbytes;
pid_t msg_lspid;
pid_t msg_lrpid;
time_t msg_stime;
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time_t msg_rtime;
time_t msg_ctime;
Here are descriptions of the fields of the msqid_ds struc-
ture:
msg_perm is an ipc_perm structure that specifies the
message operation permission (see below). This struc-
ture 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 seq; /* slot usage sequence # */
key_t key; /* key */
*msg_first is a pointer to the first message on the
queue.
*msg_last is a pointer to the last message on the
queue.
msg_cbytes is the current number of bytes on the queue.
msg_qnum is the number of messages currently on the
queue.
msg_qbytes is the maximum number of bytes allowed on
the queue.
msg_lspid is the process ID of the last process that
performed a msgsnd operation.
msg_lrpid is the process id of the last process that
performed a msgrcv operation.
msg_stime is the time of the last msgsnd operation.
msg_rtime is the time of the last msgrcv operation
msg_ctime is the time of the last msgctl operation that
changed a member of the above structure.
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Message Operation Permissions
In the msgop and msgctl system call descriptions, the per-
mission required for an operation is given as {token}, where
token is the type of permission needed, interpreted as fol-
lows:
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 on a msqid are granted to a pro-
cess if one or more of the following are true:
The effective user ID of the process is super-user.
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.
The effective group ID of the process matches
msg_perm.cgid or msg_perm.gid and the appropriate bit
of the "group" portion (060) of msg_perm.mode is set.
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.
Orphaned Process Group
A process group in which the parent of every member in the
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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 direc-
tory 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.
Process ID
Each process in the system is uniquely identified during its
lifetime by a positive integer called a process ID. A pro-
cess ID may not 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. Within a process, there are threads with
thread id's, called 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
SunOS 5.8 Last change: 14 Apr 1995 17
System Calls Intro(2)
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 ack-
nowledged by its parent process. See wait(2).
Process Group Lifetime
A process group lifetime begins when the process group is
created by its process group leader, and ends when the life-
time of the last process in the group ends or when the last
process in the group leaves the group.
Read Queue
In a stream, the message queue in a module or driver con-
taining 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 identi-
fied 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 pro-
cess need not be the root directory of the root file system.
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 prior to 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 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
following members:
struct ipc_perm sem_perm; /* operation permission struct */
struct sem *sem_base; /* ptr to first semaphore in set */
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System Calls Intro(2)
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 */
Here are descriptions of the fields of the semid_ds struc-
ture:
sem_perm 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 seq; /* slot usage sequence number */
key_t key; /* key */
sem_nsems is equal to the number of semaphores in the
set. Each semaphore in the set is referenced by a non-
negative 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 operation.
sem_ctime is the time of the last semctl operation that
changed a member of the above structure.
A semaphore is a data structure called sem that contains the
following members:
ushort semval; /* semaphore value */
pid_t sempid; /* pid of last operation */
ushort semncnt; /* # awaiting semval > cval */
ushort semzcnt; /* # awaiting semval = 0 */
semval is a non-negative integer that is the actual
value of the semaphore.
sempid is equal to the process ID of the last process
that performed a semaphore operation on this semaphore.
semncnt is a count of the number of processes that are
currently suspended awaiting this semaphore's semval to
become greater than its current value.
semzcnt is a count of the number of processes that are
currently suspended awaiting this semaphore's semval to
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System Calls Intro(2)
become 0.
Semaphore Operation Permissions
In the semop and semctl system call descriptions, the per-
mission required for an operation is given as {token}, where
token is the type of permission needed interpreted as fol-
lows:
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 on a semid are granted to a pro-
cess if one or more of the following are true:
The effective user ID of the process is super-user.
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.
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.
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 pro-
cess group leader may create a new session and process
group, becoming the session leader of the session and pro-
cess 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 pro-
cess 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.
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System Calls Intro(2)
Session Lifetime
A session lifetime begins when the session is created by its
session leader, and ends when the lifetime of the last pro-
cess 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 system 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 fol-
lowing members:
struct ipc_perm shm_perm; /* operation permission struct */
int shm_segsz; /* size of segment */
struct region *shm_reg; /* ptr to region structure */
char pad[4]; /* for swap compatibility */
pid_t shm_lpid; /* pid of last operation */
pid_t shm_cpid; /* creator pid */
ushort shm_nattch; /* number of current attaches */
ushort 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 */
Here are descriptions of the fields of the shmid_ds struc-
ture:
shm_perm 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 seq; /* slot usage sequence # */
key_t key; /* key */
shm_segsz specifies the size of the shared memory seg-
ment in bytes.
shm_cpid is the process ID of the process that created
the shared memory identifier.
shm_lpid is the process ID of the last process that
SunOS 5.8 Last change: 14 Apr 1995 21
System Calls Intro(2)
performed a shmop operation.
shm_nattch is the number of processes that currently
have this segment attached.
shm_atime is the time of the last shmat operation (see
shmop(2)).
shm_dtime is the time of the last shmdt operation (see
shmop(2)).
shm_ctime is the time of the last shmctl operation that
changed one of the members of the above structure.
Shared Memory Operation Permissions
In the shmop and shmctl system call descriptions, the per-
mission required for an operation is given as {token}, where
token is the type of permission needed interpreted as fol-
lows:
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 on a shmid are granted to a pro-
cess if one or more of the following are true:
The effective user ID of the process is super-user.
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.
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.
The appropriate bit of the "other" portion (06) of
shm_perm.mode is set.
Otherwise, the corresponding permissions are denied.
SunOS 5.8 Last change: 14 Apr 1995 22
System Calls Intro(2)
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 pro-
cessing 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 pro-
cess. The principle functions of the stream head are pro-
cessing STREAMS-related system calls, and passing data and
information between a user process and the stream.
Super-user
A process is recognized as a super-user process and is
granted special privileges, such as immunity from file per-
missions, if its effective user ID is 0.
Upstream
In a stream, the direction from driver to stream head.
Write Queue
In a stream, the message queue in a module or driver con-
taining messages moving downstream.
LIST OF SYSTEM CALLS
Name Description
access(2) determine accessibility of a
file
acct(2) enable or disable process
accounting
SunOS 5.8 Last change: 14 Apr 1995 23
System Calls Intro(2)
acl(2) get or set a file's Access Con-
trol List (ACL)
adjtime(2) correct the time to allow syn-
chronization of the system
clock
alarm(2) set a process alarm clock
audit(2) write a record to the audit log
auditon(2) manipulate auditing
auditsvc(2) write audit log to specified
file descriptor
brk(2) change the amount of space
allocated for the calling
process's data segment
chdir(2) change working directory
chmod(2) change access permission mode
of file
chown(2) change owner and group of a
file
chroot(2) change root directory
close(2) close a file descriptor
creat(2) create a new file or rewrite an
existing one
door(2) Solaris 2.5 internal implemen-
tation detail
door_call(2) See door(2)
door_create(2) See door(2)
door_info(2) See door(2)
door_return(2) See door(2)
door_revoke(2) See door(2)
dup(2) duplicate an open file descrip-
tor
exec(2) execute a file
SunOS 5.8 Last change: 14 Apr 1995 24
System Calls Intro(2)
execl(2) See exec(2)
execle(2) See exec(2)
execlp(2) See exec(2)
execv(2) See exec(2)
execve(2) See exec(2)
execvp(2) See exec(2)
_exit(2) See exit(2)
exit(2) terminate process
facl(2) See acl(2)
fchdir(2) See chdir(2)
fchmod(2) See chmod(2)
fchown(2) See chown(2)
fchroot(2) See chroot(2)
fcntl(2) file control
fork(2) create a new process
fork1(2) See fork(2)
fpathconf(2) get configurable pathname vari-
ables
fstat(2) See stat(2)
fstatvfs(2) See statvfs(2)
getaudit(2) get and set process audit
information
getauid(2) get and set user audit identity
getcontext(2) get and set current user con-
text
getdents(2) read directory entries and put
in a file system independent
format
getegid(2) See getuid(2)
SunOS 5.8 Last change: 14 Apr 1995 25
System Calls Intro(2)
geteuid(2) See getuid(2)
getgid(2) See getuid(2)
getgroups(2) get or set supplementary group
access list IDs
getitimer(2) get or set value of interval
timer
getmsg(2) get next message off a stream
getpgid(2) See getpid(2)
getpgrp(2) See getpid(2)
getpid(2) get process, process group, and
parent process IDs
getpmsg(2) See getmsg(2)
getppid(2) See getpid(2)
getrlimit(2) control maximum system resource
consumption
getsid(2) get or set session ID
getuid(2) get real user, effective user,
real group, and effective group
IDs
ioctl(2) control device
kill(2) send a signal to a process or a
group of processes
lchown(2) See chown(2)
link(2) link to a file
llseek(2) move extended read/write file
pointer
lseek(2) move read/write file pointer
lstat(2) See stat(2)
_lwp_cond_broadcast(2) See _lwp_cond_signal(2)
_lwp_cond_signal(2) signal a condition variable
SunOS 5.8 Last change: 14 Apr 1995 26
System Calls Intro(2)
_lwp_cond_timedwait(2) See _lwp_cond_wait(2)
_lwp_cond_wait(2) wait on a condition variable
_lwp_continue(2) See _lwp_suspend(2)
_lwp_create(2) create a new light-weight pro-
cess
_lwp_exit(2) terminate the calling LWP
_lwp_getprivate(2) See _lwp_setprivate(2)
_lwp_info(2) return the time-accounting
information of a single LWP
_lwp_kill(2) send a signal to a LWP
_lwp_makecontext(2) initialize an LWP context
_lwp_mutex_lock(2) mutual exclusion
_lwp_mutex_trylock(2) See _lwp_mutex_lock(2)
_lwp_mutex_unlock(2) See _lwp_mutex_lock(2)
_lwp_self(2) get LWP identifier
_lwp_sema_init(2) See _lwp_sema_wait(2)
_lwp_sema_post(2) See _lwp_sema_wait(2)
_lwp_sema_wait(2) semaphore operations
_lwp_setprivate(2) set/get LWP specific storage
_lwp_sigredirect(2) See _signotifywait(2)
_lwp_suspend(2) continue or suspend LWP execu-
tion
_lwp_wait(2) wait for a LWP to terminate
memcntl(2) memory management control
mincore(2) determine residency of memory
pages
mkdir(2) make a directory
mknod(2) make a directory, or a special
or ordinary file
SunOS 5.8 Last change: 14 Apr 1995 27
System Calls Intro(2)
mmap(2) map pages of memory
mount(2) mount a file system
mprotect(2) set protection of memory map-
ping
msgctl(2) message control operations
msgget(2) get message queue
msgop(2) message operations
msgrcv(2) See msgop(2)
msgsnd(2) See msgop(2)
munmap(2) unmap pages of memory
nice(2) change priority of a process
open(2) open for reading or writing
pathconf(2) See fpathconf(2)
pause(2) suspend process until signal
pipe(2) create an interprocess channel
poll(2) input/output multiplexing
p_online(2) change processor online or off-
line status
pread(2) See read(2)
priocntl(2) process scheduler control
priocntlset(2) generalized process scheduler
control
processor_bind(2) bind LWPs to a processor
processor_info(2) determine type and status of a
processor
profil(2) execution time profile
ptrace(2) allows a parent process to con-
trol the execution of a child
process
SunOS 5.8 Last change: 14 Apr 1995 28
System Calls Intro(2)
putmsg(2) send a message on a stream
putpmsg(2) See putmsg(2)
pwrite(2) See write(2)
read(2) read from file
readlink(2) read the value of a symbolic
link
readv(2) See read(2)
rename(2) change the name of a file
rmdir(2) remove a directory
sbrk(2) See brk(2)
semctl(2) semaphore control operations
semget(2) get set of semaphores
semop(2) semaphore operations
setaudit(2) See getaudit(2)
setauid(2) See getauid(2)
setcontext(2) See getcontext(2)
setegid(2) See setuid(2)
seteuid(2) See setuid(2)
setgid(2) See setuid(2)
setgroups(2) See getgroups(2)
setitimer(2) See getitimer(2)
setpgid(2) set process group ID
setpgrp(2) set process group ID
setregid(2) set real and effective group
IDs
setreuid(2) set real and effective user IDs
setrlimit(2) See getrlimit(2)
SunOS 5.8 Last change: 14 Apr 1995 29
System Calls Intro(2)
setsid(2) See getsid(2)
setuid(2) set user and group IDs
shmat(2) See shmop(2)
shmctl(2) shared memory control opera-
tions
shmdt(2) See shmop(2)
shmget(2) get shared memory segment iden-
tifier
shmop(2) shared memory operations
sigaction(2) detailed signal management
sigaltstack(2) set or get signal alternate
stack context
_signotifywait(2) deliver process signals to
specific LWPs
sigpending(2) examine signals that are
blocked and pending
sigprocmask(2) change and/or examine calling
process's signal mask
sigsend(2) send a signal to a process or a
group of processes
sigsendset(2) See sigsend(2)
sigsuspend(2) install a signal mask and
suspend process until signal
sigwait(2) wait until a signal is posted
stat(2) get file status
statvfs(2) get file system information
stime(2) set system time and date
swapctl(2) manage swap space
symlink(2) make a symbolic link to a file
sync(2) update super block
SunOS 5.8 Last change: 14 Apr 1995 30
System Calls Intro(2)
sysfs(2) get file system type informa-
tion
sysinfo(2) get and set system information
strings
time(2) get time
times(2) get process and child process
times
uadmin(2) administrative control
ulimit(2) get and set process limits
umask(2) set and get file creation mask
umount(2) unmount a file system
uname(2) get name of current operating
system
unlink(2) remove directory entry
ustat(2) get file system statistics
utime(2) set file access and modifica-
tion times
utimes(2) set file times
vfork(2) spawn new process in a virtual
memory efficient way
vhangup(2) virtually "hangup" the current
controlling terminal
wait(2) wait for child process to stop
or terminate
waitid(2) wait for child process to
change state
waitpid(2) wait for child process to
change state
write(2) write on a file
writev(2) See write(2)
yield(2) yield execution to another
lightweight process
SunOS 5.8 Last change: 14 Apr 1995 31
© 1994 Man-cgi 1.15S, Panagiotis Christias <christia@theseas.ntua.gr>
1995 Modified for Solaris 2.3, David Adams, <d.j.adams@soton.ac.uk>
Solaris Man Pages