glossary.html

unix 下的C开发手册,还用详细的例程。

newline
character.
<p>
<h4><a name = "tag_004_000_150">&nbsp;</a>link</h4>See
<xref href=direntry><a href="#tag_004_000_075">
directory entry
</a></xref>.
<p>
<h4><a name = "tag_004_000_151">&nbsp;</a>link count</h4>The number of directory entries that refer to a particular file.
<p>
<h4><a name = "tag_004_000_152">&nbsp;</a>local customs</h4>The conventions of a geographical area or territory
for such things as date, time and currency formats.
<p>
<h4><a name = "tag_004_000_153">&nbsp;</a>locale</h4>The definition of the subset of a user's environment that depends
on language and cultural conventions;
see
<xref href=locale><a href="locale.html#tag_005">
Locale
</a></xref>.
<p>
<h4><a name = "tag_004_000_154">&nbsp;</a>localisation</h4>The process of establishing information within a computer system
specific to the operation of particular native languages, local
customs and coded character sets.
<p>
<h4><a name = "tag_004_000_155">&nbsp;</a>login</h4>The unspecified activity by which a user gains access to the system.
Each login is associated with exactly one login name.
<p>
<h4><a name = "tag_004_000_156">&nbsp;</a>login name</h4>A user name that is associated with a login.
<p>
<h4><a name = "tag_004_000_157">&nbsp;</a>map</h4>To create an association between a page-aligned range of the
address-space of a process and a range of physical memory or some
memory object, such that a reference to an address in that range 
of the address-space results in a reference to the associated 
physical memory or memory object.
The mapped memory or memory object is not necessarily
memory-resident.
<p>
<h4><a name = "tag_004_000_158">&nbsp;</a>marked message</h4>A STREAMs message on which a certain flag is set.  Marking a message gives
the application protocol-specific information.  An application can use
<i><a href="../xsh/ioctl.html">ioctl()</a></i>
to determine whether a given message is marked.
<p>
<h4><a name = "tag_004_000_159">&nbsp;</a>memory object</h4>Either a file or
shared memory object.
<p>
When used in conjunction with
<i><a href="../xsh/mmap.html">mmap()</a></i>,
a memory object will appear in the address-space of the calling process.
<p>
<h4><a name = "tag_004_000_160">&nbsp;</a>message</h4>Information that can be transferred between processes
or threads by being added to and removed from a
message queue.
A message consists of a fixed-size message buffer.
<p>
<h4><a name = "tag_004_000_161">&nbsp;</a>message catalogue</h4>A file or storage area containing program messages, command prompts and
responses to prompts for a particular native language, territory and codeset.
<p>
<h4><a name = "tag_004_000_162">&nbsp;</a>message catalogue descriptor</h4>A per-process unique value
used to identify an open message catalogue.
A message catalogue descriptor may be implemented
using a file descriptor.
<p>
<h4><a name = "tag_004_000_163">&nbsp;</a>message queue</h4>An object to which messages can be added and removed.
Messages may be removed in the order in which they were added
or in priority order.
<p>
<h4><a name = "tag_004_000_164">&nbsp;</a>mode</h4>A collection of attributes that specifies a
file's type and its access permissions.
See
<xref href=fileaccperm><a href="#tag_004_000_107">
file access permissions
</a></xref>.
<p>
<h4><a name = "tag_004_000_165">&nbsp;</a>mount point</h4>Either the system root directory or a directory
for which the
<i>st_dev</i>
field of structure
<b>stat</b>
(see
<i><a href="../xsh/sysstat.h.html">&lt;sys/stat.h&gt;</a></i>)
differs from that of its parent directory.
<p>
<h4><a name = "tag_004_000_166">&nbsp;</a>multi-character collating element</h4>A sequence of two or more characters that collate as an entity.
For example, in some coded character sets, an accented
character is represented by a non-spacing accent,
followed by the letter.
Other examples are the Spanish elements
ch
and
ll.
<p>
<h4><a name = "tag_004_000_167">&nbsp;</a>mutex</h4>A synchronization object used to allow multiple
threads to serialize their access to shared data.
The name derives from the capability it provides; namely, mutual
exclusion.
The thread that has locked a mutex becomes its owner
and remains the owner until that same thread
unlocks the mutex.
<p>
<h4><a name = "tag_004_000_168">&nbsp;</a>name</h4>In the shell,
a word consisting solely of underscores, digits and alphabetics
from the portable character set (see
<xref href=charset><a href="charset.html#tag_001_001">
Portable Character Set
</a></xref>).
The first character of a name must not be a digit.
<p>
There are no explicit limits in this specification set on the sizes of
names, words (see
<xref href=word><a href="#tag_004_000_327">
word
</a></xref>),
lines or other objects.
However, other implicit limits do apply:
shell script lines produced by many of the
standard utilities cannot exceed
{LINE_MAX}
and the sum of exported variables comes under the
{ARG_MAX}
limit.
Historical shells dynamically allocate memory for
names and words and parse incoming lines a byte at a time.
Lines cannot have an arbitrary
{LINE_MAX}
limit because of historical practice such as makefiles, where
<i><a href="../xcu/make.html">make</a></i>
removes the
newline characters
associated with the commands for a target
and presents the shell with one very long line.
The text on
<b>INPUT FILES</b>
in
the <b>XCU</b> specification, <b>Section 1.9</b>, <b>Utility Description Defaults</b>
does allow a shell to run out of memory,
but it cannot have arbitrary programming limits.
<br>
<p>
<h4><a name = "tag_004_000_169">&nbsp;</a>named STREAM</h4>A STREAMS-based file descriptor that is attached to a name in the file-system
namespace.  All subsequent operations on the named STREAM act on the STREAM
that was associated with the file descriptor until the name is disassociated
from the STREAM.
<p>
<h4><a name = "tag_004_000_170">&nbsp;</a>NaN (not a number)</h4>A value that can be stored in a floating type but that is
not a valid floating point number.
Not all systems support the NaN value.
<p>
<h4><a name = "tag_004_000_171">&nbsp;</a>native language</h4>A computer user's spoken or written language,
such as
American English,
British English,
Danish,
Dutch,
French,
German,
Italian,
Japanese,
Norwegian
or
Swedish.
<p>
<h4><a name = "tag_004_000_172">&nbsp;</a>negative response</h4>An input string that matches one of the responses
acceptable to the LC_MESSAGES category keyword
<b>noexpr</b>,
matching an extended regular expression in the current locale.
See
<xref href=lc_messages><a href="locale.html#tag_005_003_006">
LC_MESSAGES
</a></xref>.
<p>
<h4><a name = "tag_004_000_173">&nbsp;</a>newline character</h4>A character
that in the output stream indicates
that printing should start at the beginning
of the next line.
The
newline
is the character designated by
'\n'
in the C language.
It is unspecified whether this character
is the exact sequence transmitted to an output device
by the system to accomplish the movement to the next line.
<p>
<h4><a name = "tag_004_000_174">&nbsp;</a>non-spacing characters</h4>A character, such as a character representing a diacritical
mark in the
ISO&nbsp;6937:1983 standard
coded character set,
which is used in combination with other characters
to form composite graphic symbols.
<p>
<h4><a name = "tag_004_000_175">&nbsp;</a>NUL</h4>A character with all bits set to zero.
<p>
<h4><a name = "tag_004_000_176">&nbsp;</a>null byte</h4>A byte with all bits set to zero.
<p>
<h4><a name = "tag_004_000_177">&nbsp;</a>null pointer</h4>The value that is obtained by converting the number 0 into a pointer;
for example,
(<b>void&nbsp;</b>*)&nbsp;0.
The C language guarantees that this value will not match that of
any legitimate pointer,
so it is used by many functions that return
pointers to indicate an error.
<p>
<h4><a name = "tag_004_000_178">&nbsp;</a>null string</h4>See
<xref href=emptystr><a href="#tag_004_000_091">
empty string
</a></xref>.
<p>
<h4><a name = "tag_004_000_179">&nbsp;</a>null wide-character code</h4><xref type="11" name="nullwidechar"></xref>
A wide-character code with all bits set to zero.
<p>
<h4><a name = "tag_004_000_180">&nbsp;</a>number sign</h4><xref type="11" name="numbersign"></xref>
The character #, also known as
<i>hash sign</i>.
<p>
<h4><a name = "tag_004_000_181">&nbsp;</a>object file</h4>A regular file containing the output of a compiler, formatted as input
to a linkage editor for linking with other object files into an
executable form.
The methods of linking are unspecified and may involve the
dynamic linking of objects at run time.
The internal format of an object file is unspecified, but a conforming
application cannot assume an object file is a text file.
<p>
<h4><a name = "tag_004_000_182">&nbsp;</a>offset maximum</h4>An attribute of an open file description representing the largest value
that can be used as a file offset.
<p>
<h4><a name = "tag_004_000_183">&nbsp;</a>open file</h4>A file that is currently associated with a file descriptor.
<br>
<p>
<h4><a name = "tag_004_000_184">&nbsp;</a>open file description</h4><xref type="11" name="openfiledes"></xref>
A record of how a process or group of processes are accessing a file.
Each file descriptor refers to exactly one open file description,
but an open file description can be referred to
by more than one file descriptor.
A file offset, file status and file access modes are attributes
of an open file description.
<p>
<h4><a name = "tag_004_000_185">&nbsp;</a>operand</h4>An argument to a command
that is generally used as an object
supplying information to a
utility necessary to complete its processing.
Operands generally follow the options in a command line.
See
<xref href=utilarg><a href="utilconv.html#tag_009_001">
Utility Argument Syntax
</a></xref>.
<p>
<h4><a name = "tag_004_000_186">&nbsp;</a>operator</h4>In the shell,
either a control operator or a redirection operator.
<p>
<h4><a name = "tag_004_000_187">&nbsp;</a>option</h4>An argument to a command
that is generally used to specify changes in the
utility's
default behaviour;
see
<xref href=utilarg><a href="utilconv.html#tag_009_001">
Utility Argument Syntax
</a></xref>.
<p>
<h4><a name = "tag_004_000_188">&nbsp;</a>option-argument</h4>A parameter that follows certain options.
In some cases an option-argument is included within
the same argument string as the option; in most cases it is the next argument.
See
<xref href=utilarg><a href="utilconv.html#tag_009_001">
Utility Argument Syntax
</a></xref>.
<p>
<h4><a name = "tag_004_000_189">&nbsp;</a>orphaned process group</h4>A process group in which the parent of every member is either itself a member
of the group or is not a member of the group's session.
<p>
<h4><a name = "tag_004_000_190">&nbsp;</a>page</h4>The granularity of process memory mapping or locking.
<p>
Physical memory and memory objects can be mapped into the
address-space of a process
on page boundaries and in integral multiples of pages.
Process address-space can be locked into
memory (made memory-resident) on
page boundaries and in integral multiples of pages.
<p>
<h4><a name = "tag_004_000_191">&nbsp;</a>page size</h4>The size, in bytes, of the system unit of memory allocation, protection and
mapping.  On systems that have segment- rather than page-based memory
architectures, the term &quot;page&quot; means a segment.
<p>
<h4><a name = "tag_004_000_192">&nbsp;</a>parameter</h4>In the shell,
an entity that stores values.
There are three types of
parameters:
variables
(named parameters),
positional parameters and special parameters.
Parameter expansion is accomplished by introducing a parameter with the
"$" character.
See the <b>XCU</b> specification, <a href="../xcu/chap2.html#tag_001_005"><b>Parameters and Variables</b>&nbsp;</a>.
<p>
In the C language, an object declared as part of a function declaration
or definition that acquires a value on entry to the function,
or an identifier following the macro name in a
function-like macro definition.
<p>
<h4><a name = "tag_004_000_193">&nbsp;</a>parent directory</h4>When discussing a given directory,
the directory that both contains a directory entry
for the given directory and is represented by
the pathname dot-dot in the given directory.
<p>
When discussing other types of files,
a directory containing a
directory entry for the file under discussion.
<p>
This concept does not apply to dot and dot-dot.
<p>
<h4><a name = "tag_004_000_194">&nbsp;</a>parent process</h4>See
<xref href=processdef><a href="#tag_004_000_216">
process
</a></xref>.
<p>
<h4><a name = "tag_004_000_195">&nbsp;</a>parent process ID</h4>An attribute of a new process identifying the parent of the process.
The parent process ID of a process is the process ID
of its creator, for the lifetime of the creator.
After the creator's lifetime has ended, the
parent process ID
is the
process ID
of an implementation-dependent
system process.
<p>
<h4><a name = "tag_004_000_196">&nbsp;</a>pathname</h4>A character string that is used to identify a file.
A pathname consists of, at most,
{PATH_MAX}
bytes, including the terminating null byte.
It has an optional beginning slash,
followed by zero or more filenames separated by slashes.
If the pathname refers to a directory,
it may also have one or more trailin