+.SH
+.LG
+.ce
+Section 2.
+.SM
+.sp
+.PP
+The most important change in section 2 is that the documentation
+has been significantly improved. Manual page entries now indicate
+the possible error codes which may be returned and how to interpret
+them. The introduction to section 2 now includes a glossary of
+terms used throughout the section. The terminology and formatting
+have been made consistent. Many manual pages now have ``NOTES''
+or ``CAVEATS'' providing useful information heretofore left out
+for the sake of brevity. As always the manual pages are still for
+the programmer; they are terse and extremely concise. The ``4.2BSD
+System Manual'' is likewise concise, but a bit more verbose in
+providing an overall picture of the system facilities.
+.PP
+With regard to changes in the facilities, these fall into three
+major categories: interprocess communication, signals, and file
+system related calls. The interprocess communication facilities
+center around the \fIsocket\fP mechanism described in the
+``A 4.2BSD Interprocess Communication Primer''. The new signals
+do not have an accompanying document, so the manual pages should
+be studied carefully. The new file system calls pretty much stand
+on their own, with a late section of the document
+``A Fast File System for UNIX'' supplying a quick overview of the
+most important new file system facilities. Finally, it should
+be noted that the job control facilities introduced in 4.1BSD have
+been adopted as a standard part of 4.2BSD. No special distinction
+is given to these calls (in 4.1BSD they were earmarked ``2J'').
+.PP
+Many of the new system calls have both a ``set'' and a ``get''
+form. Only the ``get'' forms are indicated below. Consult
+the manual for details on the ``set'' form.
+.BP intro
+Has been updated to reflect the new list of possible error
+codes. Now includes a glossary of terminology used in section 2.
+.BP access
+Now has symbolic definitions for the \fImode\fP parameter defined
+in <\fIsys/file.h\fP>.
+.BP bind
+Is a new interprocess communication system call for binding
+names to sockets.
+.BP connect
+Is a new interprocess communication system call for establishing
+a connection between two sockets.
+.BP creat
+Has been obsoleted by the new \fIopen\fP interface.
+.BP fchmod
+Is a new system call which does a \fIchmod\fP operation given
+a file descriptor; useful in conjunction with the new advisory
+locking facilities.
+.BP fchown
+Is a new system call which does a \fIchown\fP operation given
+a file descriptor; useful in conjunction with the new advisory
+locking facilities.
+.BP fcntl
+Is a new system call which is useful in controlling how i/o
+is performed on a file descriptor (non-blocking i/o, signal
+drive i/o). This
+interface is compatible with the System III fcntl interface.
+.BP flock
+Is a new system call for manipulating advisory locks on
+files. Locks may be shared or exclusive and locking operations
+may be indicated as being non-blocking, in which case a
+process is not blocked if the requested lock is currently
+in use.
+.BP fstat
+Now returns a larger stat buffer; see below under stat.
+.BP fsync
+Is a new system call for synchronizing a file's in-core
+state with that on disk. Its intended use is in building
+transaction oriented facilities.
+.BP ftruncate
+Is a new system call which does a \fItruncate\fP operation given
+a file descriptor; useful in conjunction with the new advisory
+locking facilities.
+.BP getdtablesize
+Is a new system call which returns the size of the
+descriptor table.
+.BP getgroups
+Is a new system call which returns the group access list
+for the caller.
+.BP gethostid
+Is a new system call which returns the unique (hopefully)
+identifier for the current host.
+.BP gethostname
+Is a new system call which returns the name of the current host.
+.BP getitimer
+Is a new system call which gets the current value for an
+interval timer.
+.BP getpagesize
+Is a new system call which returns the system page size.
+.BP getpriority
+Is a new system call which returns the current scheduling
+priority for a specific process, a group of processes, or
+all processes owned by a user. In the latter two cases,
+the priority returned is the highest (lowest numerical
+value) enjoyed by any of the specified processes.
+.BP getrlimit
+Is a new system call which returns information about a
+resource limit. The getrlimit and setrlimit calls replace
+the old vlimit call from 4.1BSD.
+.BP getrusage
+Is a new system call which returns information about
+resource utilitization of a child process or the caller.
+This call replaces the vtimes call of 4.1BSD.
+.BP getsockopt
+Is a new interprocess communication system call which
+returns the current options present on a socket.
+.BP gettimeofday
+Is a new system call which returns the current Greenwich
+date and time, and the current timezone in which the machine is
+operating. Time is returned in seconds and microseconds
+since January 1, 1970.
+.BP ioctl
+Has been changed to encode the size of parameters and
+whether they are to be copied in, out, or in and out of
+the user address space in the \fIrequest\fP. The symbolic
+names for the various ioctl requests remain the same,
+only the numeric values have changed. A number of new ioctls exist
+for use with sockets and the network facilities. The old
+LINTRUP request has been replaced by a call to fcntl and
+the SIGIO signal.
+.BP killpg
+Has now been made a system call; in 4.1BSD it was a
+library routine.
+.BP listen
+Is a new interprocess communication system call used
+to indicate a socket will be used to listen for incoming
+connection requests.
+.BP lseek
+Now has symbolic definitions for its \fIwhence\fP
+parameter defined in <\fIsys/file.h\fP>.
+.BP mkdir
+Is a new system call which creates a directory.
+.BP mpx
+The multiplexed file facilities are no longer part
+of the system. They have been replaced by the
+socket, and related, system calls.
+.BP open
+Is different, now taking an optional third parameter
+and supporting file creation, automatic truncation,
+automatic append on write, and ``exclusive'' opens.
+The open interface has been made compatible with
+System III with the exception that non-blocking
+opens on terminal lines requiring carrier are not
+supported.
+.BP profil
+Now returns statistical information based on a 100 hz
+clock rate.
+.BP quota
+Is a new system call which is part of the disk quota
+facilities. Quota is used to manipulate disk quotas
+for a specific user, as well as perform certain random
+chores such as syncing quotas to disk.
+.BP read
+Now automatically restarts when a read on a terminal
+is interrupted by a signal before any data is read.
+.BP readv
+Is a new system call which supports scattering of
+read data into (possibly) disjoint areas of memory.
+.BP readlink
+Is a new system call for reading the value of a
+symbolic link.
+.BP recv
+Is a new interprocess communication system call
+used to receive a message on a connected socket.
+.BP recvfrom
+Is a new interprocess communication system call
+used to receive a message on a (possibly) unconnected socket.
+.BP recvmsg
+Is a new interprocess communication system call
+used to receive a message on a (possibly) unconnected socket
+which may have access rights included. When using on-machine
+communication, recvmsg and sendmsg may be used to pass
+file descriptors between processes.
+.BP rename
+Is a new system call which changes the name of an entry
+in the file system (plain file, directory, character
+special file, etc.). Rename has an important property
+in that it guarantees the target will always exist, even
+if the system crashes in the middle of the operation.
+Rename only works with source and destination in the
+same file system.
+.BP rmdir
+Is a new system call for removing a directory.
+.BP select
+Is a new system call (mainly for interprocess
+communication) which provides facility for synchronous i/o
+multiplexing. Sets of file descriptors may be queried
+for readability, writability, and if any exceptional
+conditions are present (such as out of band data on a
+socket). An optional timeout may also be supplied in
+which case the select operation will return after a
+specified period of time should no descriptor satisfy the
+requests.
+.BP send
+Is a new interprocess communication system call for
+sending a message on a connected socket.
+.BP sendto
+Is a new interprocess communication system call for
+sending a message on a (possibly) unconnected socket.
+.BP sendmsg
+Is a new interprocess communication system call for
+sending a message on a (possibly) unconnected socket
+which may included access rights.
+.BP setquota
+Is a new system call for enabling or disabling disk
+quotas on a file system.
+.BP setregid
+Is a new system call which replaces the 4.1BSD setgid
+system call. Setregid allows the real and effective
+group ID's of a process to be set separately.
+.BP setreuid
+Is a new system call which replaces the 4.1BSD setuid
+system call. Setreuid allows the real and effective
+user ID's of a process to be set separately.
+.BP shutdown
+Is a new interprocess communication system call for
+shutting down part or all of full-duplex connection.
+.BP sigblock
+Is a new system call for blocking signals during a
+critical section of code.
+.BP sigpause
+Is a new system call for blocking a set of signals
+and then pausing indefinitely for a signal to arrive.
+.BP sigsetmask
+Is a new system call for setting the set of signals
+which are currently blocked from delivery to a process.
+.BP sigstack
+Is a new system call for defining an alternate stack
+on which signals are to be processed.
+.BP sigsys
+Is no longer supported. The new signal facilities are
+a superset of those which sigsys provided.
+.BP sigvec
+Is the new system call interface for defining signal
+actions. For each signal (except SIGSTOP and SIGKILL),
+sigvec allows a ``signal vector'' to be defined. The
+signal vector is comprised of a handler, a mask of signals
+to be blocked while the handler executes, and an indication
+of whether or not the handler should execute on a signal
+stack defined by a sigstack call. The old signal interface
+is provided as a library routine with several important
+caveats. First, signal actions are no longer reset to
+their default value after a signal is delivered to a process.
+Second, while a signal handler is executing the signal which
+is being processed is blocked until the handler returns.
+To simulate the old signal interface, the user must explicitly
+reset the signal action to be the default value and unblock
+the signal being processed.
+.IP
+Four new signals have been added for the interprocess
+communication and interval timer facilities. SIGIO is
+delivered to a process when an fcntl call enables
+signal driven i/o and input is present on a terminal (and
+a signal handler is defined).
+SIGURG is delivered when an urgent condition arises on a
+socket (and a handler is defined). SIGPROF and SIGVTALRM
+are associated with the ITIMER_PROF and ITIMER_VIRTUAL
+interval timers, and delivered to a process when such
+a timer expires (the SIGALRM signal is used for the ITIMER_REAL
+interval timer). The old SIGTINT signal is replaced by
+SIGIO.
+.BP socket
+Is a new interprocess communication system call for
+creating a socket.
+.BP socketpair
+Is a new interprocess communication system call for
+creating a pair of connected and unnamed sockets.
+.BP stat
+Now returns a larger structure. New fields are present
+indicating the optimal blocking factor in which i/o
+should be performed (for disk files the block size of
+the underlying file system) and the actual number of
+disk blocks allocated to the file. Inode numbers are
+now 32-bit quantities. Several spare fields have been
+allocated for future expansion. These include space
+for 64-bit file sizes and 64-bit time stamps. Two new
+file types may be returned, S_IFLNK for symbolic
+links, and S_IFSOCK for sockets residing in the file system.
+.BP swapon
+Has been renamed from the vswapon call of 4.1BSD.
+.BP symlink
+Is a new system call for creating a symbolic link.
+.BP truncate
+Is a new system call for truncating a file to a
+specific size.
+.BP unlink
+Should no longer be used for removing directories.
+Directories should only be created with mkdir and
+removed with rmdir. Creating hard links to directories
+can cause disastrous results.
+.BP utime
+Is defunct, replaced by utimes.
+.BP utimes
+Is a new system call which uses the new time format
+in setting the accessed and updated times on a file.
+.BP vfork
+Is still present, but definitely on its way out.
+Future plans include implementing fork with a scheme
+in which pages are initially shared read-only. On
+the first attempt by a process to write on a page
+the parent and child would receive separate writable
+copies of the page.
+.BP vlimit
+Is no longer supported. Vlimit is replaced by the
+getrlimit and setrlimit calls.
+.BP vread
+Is no longer supported in the system.
+.BP vswapon
+Has been renamed swapon.
+.BP vtimes
+Is no longer supported. Vtimes is replaced by the
+getrusage call.
+.BP vwrite
+Is no longer supported in the system.
+.BP wait
+Now is automatically restarted when interrupted
+by a signal before status could be returned.
+.BP wait3
+Returns resource usage in a different format than
+that which was returned in 4.1BSD. This structure
+is compatible with the new getrusage system call.
+Wait3 is now automatically restarted when interrupted
+by a signal before status could be returned.
+.BP write
+Now is automatically restarted when writing on a
+terminal and interrupted by a signal before any
+i/o was completed.
+.BP writev
+Is a new version of the write system call which
+supports gathering of data in (possibly)
+discontiguous areas of memory
projects / unix-history / commitdiff