glossary.html

unix 下的C开发手册,还用详细的例程。

message catalogue descriptors and
directory streams.
See
<xref href=openfiledes><a href="#tag_004_000_184">
open file description
</a></xref>
and
{OPEN_MAX}
in
<i><a href="../xsh/limits.h.html">&lt;limits.h&gt;</a></i>.
<p>
<h4><a name = "tag_004_000_110">&nbsp;</a>file group class</h4>The property of a file indicating access permissions
for a process related to the group identification of a process.
A process is in the file group class
of a file if the process is not in the
file owner class and if the effective group ID
or one of the supplementary group IDs
of the process matches the group ID
associated with the file.
Other members of the class may be implementation-dependent.
<p>
<h4><a name = "tag_004_000_111">&nbsp;</a>file hierarchy</h4>Files in the system are organised in a hierarchical structure in which
all of the non-terminal nodes are directories and all of the terminal
nodes are any other type of file.
Because multiple directory entries may refer to the same file, the
hierarchy is properly described as a
<i>directed graph.</i>
<p>
<h4><a name = "tag_004_000_112">&nbsp;</a>file mode</h4>An object containing the
<i>file mode bits</i>
and file type of a file, as described in
<i><a href="../xsh/sysstat.h.html">&lt;sys/stat.h&gt;</a></i>.
<p>
<h4><a name = "tag_004_000_113">&nbsp;</a>file mode bits</h4>A file's file permission bits,
set-user-ID-on-execution bit
(S_ISUID)
and set-group-ID-on-execution bit
(S_ISGID);
see
<i><a href="../xsh/sysstat.h.html">&lt;sys/stat.h&gt;</a></i>.
<p>
<h4><a name = "tag_004_000_114">&nbsp;</a>filename</h4><xref type="11" name="filename"></xref>
A name consisting of 1 to
{NAME_MAX}
bytes used to name a file.
The characters composing the name
may be selected from the set of all
character values excluding the
slash character and the null byte.
The filenames dot and dot-dot have special meaning;
see
<xref href=pathres><a href="#tag_004_000_198">
pathname resolution
</a></xref>.
A
filename
is sometimes referred to as a
<i>pathname component</i>.
<p>
Filenames should be constructed from the
portable filename character set
because the use of other
characters can be confusing or ambiguous in certain contexts.
(For instance, the use of a colon (:) in a pathname could cause
ambiguity if that pathname were included in a
<i>PATH</i>
definition.)
<p>
<h4><a name = "tag_004_000_115">&nbsp;</a>file offset</h4>The byte position in the file where the next I/O operation begins.
Each open file description associated with a regular file,
block special file or directory has a file offset.
A character special file that does not refer to a
terminal device may have a file offset.
There is no file offset specified for a pipe
or FIFO.
<p>
<h4><a name = "tag_004_000_116">&nbsp;</a>file other class</h4>The property of a file indicating access permissions
for a process related to the user and group identification of a process.
A process is in the file other class of a file if the process
is not in the file owner class or file group class.
<p>
<h4><a name = "tag_004_000_117">&nbsp;</a>file owner class</h4>The property of a file indicating access permissions
for a process related to the user identification of a process.
A process is in the file owner class of a file if the
effective user ID
of the process matches the user ID of the file.
<p>
<h4><a name = "tag_004_000_118">&nbsp;</a>file permission bits</h4>Information about a file that is used,
along with other information, to determine if a
process has read, write or execute/search permission to a file.
The bits are divided into three parts:
owner, group and other.
Each part is used with the corresponding file class of
processes.
These bits are contained in the
file mode,
as described in
<i><a href="../xsh/sysstat.h.html">&lt;sys/stat.h&gt;</a></i>.
The detailed usage of the
file permission bits
in access decisions is described in
<xref href=fileaccperm><a href="#tag_004_000_107">
file access permissions
</a></xref>.
<p>
<h4><a name = "tag_004_000_119">&nbsp;</a>file serial number</h4>A per-file-system unique identifier for a file.
<p>
<h4><a name = "tag_004_000_120">&nbsp;</a>file system</h4>A collection of files and certain of their attributes.
It provides a name space for file serial numbers referring to those files.
<p>
<h4><a name = "tag_004_000_121">&nbsp;</a>file times update</h4>Each file has three associated time values that are updated when file
data has been accessed, file data has been modified, or file status
has been changed, respectively.
These values are returned in the file
characteristics structure, as described in
<i><a href="../xsh/sysstat.h.html">&lt;sys/stat.h&gt;</a></i>.
<p>
For each function or utility
in this specification set that reads or writes file data or
changes the file status, the appropriate time-related fields are noted
as &quot;marked for update&quot;.
At an update point in time, any marked
fields are set to the current time and the update marks cleared.
Two such update points are when the file is no longer open by any process
and when
<i><a href="../xsh/stat.html">stat()</a></i>
or
<i><a href="../xsh/fstat.html">fstat()</a></i>
is performed on the file.
Additional update points are unspecified.
Marks for update, and updates themselves, are not
done for files on read-only file systems.
<p>
<h4><a name = "tag_004_000_122">&nbsp;</a>file type</h4>See
<xref href=filedef><a href="#tag_004_000_106">
file
</a></xref>.
<p>
<h4><a name = "tag_004_000_123">&nbsp;</a>filter</h4>A command whose operation consists of reading data from
standard input or a list of input files
and writing data to standard output.
Typically, its function is to perform some transformation
on the data stream.
<p>
<h4><a name = "tag_004_000_124">&nbsp;</a>first open (of a file)</h4>When a process opens a file
that is not currently an open file within any process.
<p>
<h4><a name = "tag_004_000_125">&nbsp;</a>foreground job</h4>See
<xref href=fgprocgrp><a href="#tag_004_000_127">
foreground process group
</a></xref>.
<p>
<h4><a name = "tag_004_000_126">&nbsp;</a>foreground process</h4>A process that is a member of a foreground process group.
<p>
<h4><a name = "tag_004_000_127">&nbsp;</a>foreground process group</h4><xref type="11" name="fgprocgrp"></xref>
(Or <b>foreground job</b>.)
A process group whose member processes have certain privileges,
denied to processes in background process groups,
when accessing their controlling terminal.
Each session that has established a connection with a controlling
terminal has exactly one process group of the session as the foreground
process group of that controlling terminal.  See
<xref href=genterm><a href="termios.html#tag_008">
General Terminal Interface
</a></xref>.
<p>
<h4><a name = "tag_004_000_128">&nbsp;</a>foreground process group ID</h4>The process group ID of the foreground process group.
<p>
<h4><a name = "tag_004_000_129">&nbsp;</a>form-feed character</h4>A character that in the output stream indicates
that printing should start on the next page of an output device.
The
form-feed
is the character
designated by
'\f'
in the C language.
If
the form-feed
is not the first character
of an output line, the result is unspecified.
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 page.
<p>
<h4><a name = "tag_004_000_130">&nbsp;</a>graphic character</h4>A character, other than a control character,
that has a visual representation
when handwritten, printed or displayed.
<p>
<h4><a name = "tag_004_000_131">&nbsp;</a>group database</h4><xref type="11" name="groupdb"></xref>
A system database of implementation-dependent format that
contains at least the following information for each group ID:
<ul>
<p>
<li>
Group Name
<p>
<li>
Numerical Group ID
<p>
<li>
List of users allowed in the group.
<p>
</ul>
<p>
The list of users allowed in the group is used by the
<i><a href="../xcu/newgrp.html">newgrp</a></i>
utility.
<p>
<h4><a name = "tag_004_000_132">&nbsp;</a>group ID</h4><xref type="11" name="groupid"></xref>
A non-negative integer
that is used to identify a group of system users.
Each system user is a member of at least one group.
When the identity of a group is associated with a
process, a group ID value is referred to as a
real group ID,
an effective group ID,
one of the
supplementary group IDs or a saved set-group-ID.
<p>
<h4><a name = "tag_004_000_133">&nbsp;</a>group name</h4>A string that is used to identify a group, as described in
<xref href=groupdb><a href="#tag_004_000_131">
group database
</a></xref>.
To be portable across
XSI-conformant systems, the value must be composed of characters
from the portable filename character set.
The hyphen should not be used as the first character
of a portable group name.
<p>
<h4><a name = "tag_004_000_134">&nbsp;</a>hard limit</h4>A system resource limitation that may be reset to a lesser or greater limit
by a privileged process.  A non-privileged process is restricted to only
lowering its hard limit.
<p>
<h4><a name = "tag_004_000_135">&nbsp;</a>hard link</h4>The relationship between two
directory entries
that represent the same file;
see
<xref href=direntry><a href="#tag_004_000_075">
directory entry
</a></xref>.
This term is contrasted against
<b>symbolic link</b>;
see
<xref href=GLsymlink><a href="#tag_004_000_289">
symbolic link
</a></xref>.
<p>
<h4><a name = "tag_004_000_136">&nbsp;</a>home directory</h4>The current directory associated with a user
at the time of login.
<p>
<h4><a name = "tag_004_000_137">&nbsp;</a>incomplete line</h4>A sequence of one or more non-newline
characters at the end of the file.
<p>
<h4><a name = "tag_004_000_138">&nbsp;</a>Inf</h4>A value representing infinity that can be stored in a floating type.
Not all systems support the Inf value.
<p>
<h4><a name = "tag_004_000_139">&nbsp;</a>interactive shell</h4>A processing mode of the shell that is suitable for direct user interaction.
<p>
<h4><a name = "tag_004_000_140">&nbsp;</a>internationalisation</h4>The provision within a computer program of the capability
of making itself adaptable to the requirements of
different native languages, local customs and
coded character sets.
<p>
<h4><a name = "tag_004_000_141">&nbsp;</a>invoke</h4><xref type="11" name="invoke"></xref>
To perform the actions described in
the <b>XCU</b> specification, <a href="../xcu/chap2.html#tag_001_009_001_001"><b>Command Search and Execution</b>&nbsp;</a>,
except that searching for shell functions
and special built-in
utilities is suppressed.
See also
<xref href=execute><a href="#tag_004_000_097">
execute
</a></xref>.
<p>
<h4><a name = "tag_004_000_142">&nbsp;</a>ISO/IEC&nbsp;646:1983</h4>ISO 7-bit coded character set for information interchange.
The reference version of the standard
contains 95 graphic characters,
which are identical to the graphic characters defined in the
ASCII coded character set.
<p>
<h4><a name = "tag_004_000_143">&nbsp;</a>ISO&nbsp;6937:1983</h4>ISO 7-bit or 8-bit coded character set for text communication
using public communication networks, private communication networks,
or interchange media such as magnetic tapes and discs.
<p>
<h4><a name = "tag_004_000_144">&nbsp;</a>ISO&nbsp;8859-1:1987</h4>ISO 8-bit single-byte coded character set Part 1,
Latin Alphabet No 1.
This standard
character set comprises 191 graphic characters
covering the requirements of most of Western Europe.
<p>
<h4><a name = "tag_004_000_145">&nbsp;</a>job</h4>A set of processes, comprising a shell pipeline,
and any processes descended from it,
that are all in the same process group.
See the definition of
<b>pipeline</b>
in the <b>XCU</b> specification, <a href="../xcu/chap2.html#tag_001_009_002"><b>Pipelines</b>&nbsp;</a>.
<p>
<h4><a name = "tag_004_000_146">&nbsp;</a>job control</h4>A facility that allows
users selectively to stop (suspend) the execution of
processes
and continue (resume) their execution at a later point.
The user typically employs this facility via the interactive interface
jointly supplied by the terminal I/O
driver and a command interpreter.
<br>
<p>
<h4><a name = "tag_004_000_147">&nbsp;</a>job control job ID</h4>A handle that is used to refer to a job.
The job control job ID can be any of the forms shown in
the following table:
<pre>
<table  bordercolor=#000000 border=1 align=center><tr valign=top><th align=center><b>Job Control Job ID</b>
<th align=center><b>Meaning</b>
<tr valign=top><td align=left>%%
<td align=left>Current job
<tr valign=top><td align=left>%+
<td align=left>Current job
<tr valign=top><td align=left>%-
<td align=left>Previous job
<tr valign=top><td align=left>%<i>n</i>
<td align=left>Job number <i>n</i>
<tr valign=top><td align=left>%<i>string</i>
<td align=left>Job whose command begins with <i>string</i>
<tr valign=top><td align=left>%?<i>string</i>
<td align=left>Job whose command contains <i>string</i>
</table>

<h6 align=center><xref table="Job Control Job ID Formats"><a name="tagt_4">&nbsp;</a></xref>Table: Job Control Job ID Formats</h6>
</pre>
<p>
<h4><a name = "tag_004_000_148">&nbsp;</a>last close (of a file)</h4>When a process closes a file,
resulting in the file not being an open file within any process.
<p>
<h4><a name = "tag_004_000_149">&nbsp;</a>line</h4>A sequence of zero or more non-newline
characters plus a terminating