FreeBSD Manual Pages
Intro(2) Intro(2) NAME Intro, intro - introduction to system calls and error numbers SYNOPSIS #include <errno.h> 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 condi- tion is indicated by an otherwise impossible return value. This is al- most 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 spec- ified on the command line at compilation time (see threads(5)). 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 detec- tion 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 process- ing a function call, any one of the possible errors might may be re- turned, as the order of detection is undefined. See standards(5) for additional information regarding the Single UNIX Specification. Each system call description attempts to list all possible error num- bers. 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 docu- ment 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 cor- responds 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, oc- curred during a system service function. If ex- ecution 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 er- ror 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 ex- ported shell variables. 8 ENOEXEC Exec format error A request is made to execute a file which, al- though 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(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 be- cause the system's process table is full or the user is not allowed to create any more pro- cesses, or a call failed because of insuffi- cient 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 func- tions, a program asks for more space than the system is able to supply. This is not a tempo- rary 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 segmenta- tion 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 docu- ment which privileges are needed to override the protection system. 14 EFAULT Bad address The system encountered a hardware fault in at- tempting 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 sys- tems 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 un- mount 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_ON- LINE. 17 EEXIST File exists An existing file was mentioned in an inappro- priate context (for example, call to the link(2) function). 18 EXDEV Cross-device link A hard link to a file on another device was at- tempted. 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 speci- fying 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 re- move a pure-procedure program that is being ex- ecuted. (This message is obsolete.) 27 EFBIG File too large The size of the file exceeded the limit speci- fied by resource RLIMIT_FSIZEn; the file size exceeds the maximum supported by the file sys- tem; or the file size exceeds the offset maxi- mum of the file descriptor. See the File De- scriptor 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 set- ting or removing of record locks on a file can- not 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 gen- erates 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 preci- sion. 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 mes- sage 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 ms- gctl(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, condi- tion 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 can- celed 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 al- location 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-spe- cific 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 indeter- minate. 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 struc- tures were available. This is a temporary con- dition; one may recover from it if other pro- cesses release resources. 65 ENOPKG Package not installed This error occurs when users attempt to use a call from a package which has not been in- stalled. 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 ex- ceeds NAME_MAX while _POSIX_NO_TRUNC is in ef- fect; 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 per- mission 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 prob- ably 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 87 ELIBEXEC Cannot exec a shared library directly Attempting to exec a shared library directly. 88 EILSEQ Error 88 Illegal byte sequence. Handle multiple charac- ters 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 opera- tion on a transport endpoint. Destination ad- dress 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 get- ting 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 ex- ists. Used for the Internet protocols. 124 EAFNOSUPPORT Address family not supported by protocol family An address incompatible with the requested pro- tocol 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 ma- chine. 127 ENETDOWN Network is down Operation encountered a dead network. 128 ENETUNREACH Network is unreachable Operation was attempted to an unreachable net- work. 129 ENETRESET Network dropped connection because of reset The host you were connected to crashed and re- booted. 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 con- nection 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 con- nected transport endpoint; or, a sendto(3SOCKET) or sendmsg(3SOCKET) request on a connected transport endpoint specified a des- tination when already connected. 134 ENOTCONN Transport endpoint is not connected A request to send or receive data was disal- lowed because the transport endpoint is not connected and (when sending a datagram) no ad- dress 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 re- sults 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 ses- sion that has established a connection with a controlling terminal. Controlling Process A session leader that established a connection to a controlling termi- nal. 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 se- quences 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 catalogs the list of files, including directories (sub-directories), that are di- rectly 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 directory. 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 peripheral hard- ware 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 ef- fective 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 cor- responding 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 in- terpretation 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 con- dition 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 ter- minal will distinguish one process group of the session as the fore- ground process group of the controlling terminal. This group has cer- tain 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 de- fined 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 func- tion 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 struc- ture 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 per- formed a msgsnd() operation. The msg_lrpid member is the process id of the last process that per- formed 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 descrip- tions, 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 appropri- ate 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 out- put 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 up- stream) 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 con- structing them and for connecting multiplexed configurations of streams. Offset Maximum An offset maximum is an attribute of an open file description repre- senting 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 ei- ther 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 op- tional 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 direc- tory. 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 re- stricted operations. Prior to the Solaris 10 release, a process running with uid 0 was granted all privileges. See privileges(5) for the seman- tics 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 life- time, 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 iden- tified 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 pro- cessor sets. A process bound to one of these sets will run only on pro- cessors 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 mes- sages 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 responsi- ble 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 direc- tory 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 de- scribed 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 struc- ture 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 sema- phore 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 re- ferred 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 be- come 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 be- come 0. Semaphore Operation Permissions In the semop(2) and semctl(2) function descriptions, the permission re- quired 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 ses- sion 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 ses- sion 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 cre- ated 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 descrip- tions, 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 an- cestor 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 ser- vices 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 rou- tines, 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 func- tions 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 mes- sages moving downstream. standards(5), threads(5) 4 Oct 2005 Intro(2)
NAME | SYNOPSIS | DEFINITIONS
Want to link to this manual page? Use this URL:
<https://man.freebsd.org/cgi/man.cgi?query=intro&sektion=2&manpath=SunOS+5.10>