glossary.htm

the unix power tools

></DT
><DD
CLASS="glossdef"
><P
CLASS="para"
>The character <CODE
CLASS="literal"
>/</CODE
>.
It separates elements in a pathname.
<EM
CLASS="emphasis"
>See also</EM
> article
<A
CLASS="xref"
HREF="ch01_21.htm"
TITLE="Making Pathnames "
>1.21</A
>,
<A
CLASS="xref"
HREF="glossary.htm#GLOSS-BACKSLASH"
TITLE=""
>backslash</A
>.</P
></DD
><DT
CLASS="glossterm"
><A
CLASS="glossterm"
NAME="GLOSS-SINGLE-QUOTE"
>single quote</A
></DT
><DD
CLASS="glossdef"
><P
CLASS="para"
>The <CODE
CLASS="literal"
>'</CODE
> character.
This isn't the same as a backquote (<CODE
CLASS="literal"
>`</CODE
>).
The single quote is used around a part of a UNIX command line where the shell 
should do no interpretation (except history substitution in the C shell).
<EM
CLASS="emphasis"
>See also</EM
> articles
<A
CLASS="xref"
HREF="ch08_14.htm"
TITLE="Bourne Shell Quoting "
>8.14</A
>
and
<A
CLASS="xref"
HREF="ch08_15.htm"
TITLE="Differences Between Bourne and C Shell Quoting "
>8.15</A
>,
<A
CLASS="xref"
HREF="glossary.htm#GLOSS-DOUBLE-QUOTE"
TITLE=""
>double quote</A
>.</P
></DD
><DT
CLASS="glossterm"
><A
CLASS="glossterm"
NAME="GLOSS-SPECIAL-FILE"
>special file</A
></DT
><DD
CLASS="glossdef"
><P
CLASS="para"
>An entity in the filesystem that accesses I/O devices. There is a
special file for every terminal, every network controller, every
partition of every disk drive, and every possible way of accessing
every tape drive.
<EM
CLASS="emphasis"
>See also</EM
> article
<A
CLASS="xref"
HREF="ch01_29.htm"
TITLE="When Is a File Not a File? "
>1.29</A
>.</P
></DD
><DT
CLASS="glossterm"
><A
CLASS="glossterm"
NAME="GLOSS-STRING"
>string</A
></DT
><DD
CLASS="glossdef"
><P
CLASS="para"
>A sequence of characters.
<EM
CLASS="emphasis"
>See also</EM
>
<A
CLASS="xref"
HREF="glossary.htm#GLOSS-WORD"
TITLE=""
>word</A
>.</P
></DD
><DT
CLASS="glossterm"
><A
CLASS="glossterm"
NAME="GLOSS-SUBDIRECTORY"
>subdirectory</A
></DT
><DD
CLASS="glossdef"
><P
CLASS="para"
>A directory within a directory.
<EM
CLASS="emphasis"
>See also</EM
> articles
<A
CLASS="xref"
HREF="ch01_21.htm"
TITLE="Making Pathnames "
>1.21</A
>
and
<A
CLASS="xref"
HREF="ch04_07.htm"
TITLE="Make More Directories! "
>4.7</A
>.</P
></DD
><DT
CLASS="glossterm"
><A
CLASS="glossterm"
NAME="GLOSS-SWAPPING"
>swapping</A
></DT
><DD
CLASS="glossdef"
><P
CLASS="para"
>A technique that the UNIX kernel uses to clean up physical memory.
The kernel moves entire processes from memory to disk and then
reassigns the memory to some other function. Processes that have been
idle for more than a certain period may be removed from memory to save space.
Swapping is also used to satisfy extreme memory shortages. When the
system is extremely short of memory, active processes may be &quot;swapped out.&quot;</P
></DD
><DT
CLASS="glossterm"
><A
CLASS="glossterm"
NAME="GLOSS-SWITCH"
>switch</A
></DT
><DD
CLASS="glossdef"
><P
CLASS="para"
><EM
CLASS="emphasis"
>See</EM
>
<A
CLASS="xref"
HREF="glossary.htm#GLOSS-OPTION-SWITCH"
TITLE=""
>option switch</A
>.</P
></DD
><DT
CLASS="glossterm"
><A
CLASS="glossterm"
NAME="GLOSS-SYSTEM-CALL"
>system call</A
></DT
><DD
CLASS="glossdef"
><P
CLASS="para"
>The lowest-level access to the UNIX operating system.
Everything else in UNIX is built on system calls.
<EM
CLASS="emphasis"
>See also</EM
>
<A
CLASS="xref"
HREF="glossary.htm#GLOSS-LIBRARY-FUNCTION"
TITLE=""
>library function</A
>.</P
></DD
><DT
CLASS="glossterm"
><A
CLASS="glossterm"
NAME="GLOSS-SYSTEM-V-UNIX"
>System V UNIX</A
></DT
><DD
CLASS="glossdef"
><P
CLASS="para"
>A version of UNIX from AT&amp;T.
The most recent Release of System&nbsp;V is Release&nbsp;4, known as V.4 or SVR4.</P
></DD
><DT
CLASS="glossterm"
><A
CLASS="glossterm"
NAME="GLOSS-TCP-IP"
>TCP/IP</A
></DT
><DD
CLASS="glossdef"
><P
CLASS="para"
>A network protocol that is commonly used for communications via an Ethernet.
TCP/IP is also called the &quot;Internet protocol.&quot; It is also common to
use TCP/IP over leased lines for long-distance communications.</P
></DD
><DT
CLASS="glossterm"
><A
CLASS="glossterm"
NAME="GLOSS-TERMCAP"
>termcap</A
></DT
><DD
CLASS="glossdef"
><P
CLASS="para"
>Stands for <EM
CLASS="emphasis"
>term</EM
>inal <EM
CLASS="emphasis"
>cap</EM
>abilities, an early (and still common)
way to describe terminals to UNIX.
<EM
CLASS="emphasis"
>See also</EM
> article
<A
CLASS="xref"
HREF="ch41_11.htm"
TITLE="How termcap and terminfo Describe Terminals "
>41.11</A
>,
<A
CLASS="xref"
HREF="glossary.htm#GLOSS-TERMINFO"
TITLE=""
>terminfo</A
>.</P
></DD
><DT
CLASS="glossterm"
><A
CLASS="glossterm"
NAME="GLOSS-TERMINAL-EMULATOR"
>terminal emulator</A
></DT
><DD
CLASS="glossdef"
><P
CLASS="para"
>A program that makes a computer display emulate (act like) a terminal.
For example, many terminal emulator programs emulate the Digital
Equipment Corporation VT100 terminal.</P
></DD
><DT
CLASS="glossterm"
><A
CLASS="glossterm"
NAME="GLOSS-TERMINFO"
>terminfo</A
></DT
><DD
CLASS="glossdef"
><P
CLASS="para"
>A newer way to describe terminal capabilities to UNIX.
<EM
CLASS="emphasis"
>See also</EM
> article
<A
CLASS="xref"
HREF="ch41_11.htm"
TITLE="How termcap and terminfo Describe Terminals "
>41.11</A
>,
<A
CLASS="xref"
HREF="glossary.htm#GLOSS-TERMCAP"
TITLE=""
>termcap</A
>.</P
></DD
><DT
CLASS="glossterm"
><A
CLASS="glossterm"
NAME="GLOSS-THE-NET"
>the Net</A
></DT
><DD
CLASS="glossdef"
><P
CLASS="para"
>A term for two particular networks:
<SPAN
CLASS="link"
>Usenet and Internet (<A
CLASS="linkend"
HREF="ch01_33.htm"
TITLE="UNIX Networking and Communications "
>1.33</A
>)</SPAN
>.
For instance, &quot;I read it on the Net&quot; or &quot;You can get that file on the Net.&quot;</P
></DD
><DT
CLASS="glossterm"
><A
CLASS="glossterm"
NAME="GLOSS-TIMESTAMP"
>timestamp</A
></DT
><DD
CLASS="glossdef"
><P
CLASS="para"
>The UNIX filesystem stores the times that each file was last
modified, accessed, or had a change to its inode.
These times&nbsp;- especially the modification time&nbsp;- are often called
<EM
CLASS="emphasis"
>timestamps</EM
>.
<EM
CLASS="emphasis"
>See also</EM
> article
<A
CLASS="xref"
HREF="ch21_13.htm"
TITLE="Read an Inode with stat "
>21.13</A
>.</P
></DD
><DT
CLASS="glossterm"
><A
CLASS="glossterm"
NAME="GLOSS-TRUNCATE"
>truncate</A
></DT
><DD
CLASS="glossdef"
><P
CLASS="para"
>To cut, to shorten&nbsp;- for example, &quot;truncate a file after line&nbsp;10&quot; means
to remove all lines after line&nbsp;10.</P
></DD
><DT
CLASS="glossterm"
><A
CLASS="glossterm"
NAME="GLOSS-UUENCODE-UUDECODE"
>uuencode, uudecode</A
></DT
><DD
CLASS="glossdef"
><P
CLASS="para"
>Utilities that encode files with binary (8-bit) characters into an ASCII
(7-bit) format&nbsp;- and decode them back into the original binary format.
This is used for transferring data across communications links that
can't transfer binary (8-bit) data.
<EM
CLASS="emphasis"
>See also</EM
> article
<A
CLASS="xref"
HREF="ch19_05.htm"
TITLE="Using tar to Create and Unpack Archives "
>19.5</A
>.</P
></DD
><DT
CLASS="glossterm"
><A
CLASS="glossterm"
NAME="GLOSS-VAX-VMS"
>VAX/VMS</A
></DT
><DD
CLASS="glossdef"
><P
CLASS="para"
>A popular computer operating system from the Digital Equipment Corporation.</P
></DD
><DT
CLASS="glossterm"
><A
CLASS="glossterm"
NAME="GLOSS-WEDGED"
>wedged</A
></DT
><DD
CLASS="glossdef"
><P
CLASS="para"
>A terminal or program is <EM
CLASS="emphasis"
>wedged</EM
> when it's &quot;frozen&quot; or &quot;stuck.&quot;
The normal activity stops and often can't be restarted without
resetting the terminal or killing the program.</P
></DD
><DT
CLASS="glossterm"
><A
CLASS="glossterm"
NAME="GLOSS-WHITE-SPACE"
>white space</A
></DT
><DD
CLASS="glossdef"
><P
CLASS="para"
>A series of one or more space or TAB characters.</P
></DD
><DT
CLASS="glossterm"
><A
CLASS="glossterm"
NAME="GLOSS-WORD"
>word</A
></DT
><DD
CLASS="glossdef"
><P
CLASS="para"
>Similar to a word in a spoken language like English, a word is a unit
made up of one or more characters.
But unlike English,
words in UNIX can contain white space; they can also have no
characters (a <EM
CLASS="emphasis"
>zero-length</EM
> word).
<EM
CLASS="emphasis"
>See also</EM
>
<A
CLASS="xref"
HREF="glossary.htm#GLOSS-ARGUMENT"
TITLE=""
>argument</A
>.</P
></DD
><DT
CLASS="glossterm"
><A
CLASS="glossterm"
NAME="GLOSS-XENIX"
>XENIX</A
></DT
><DD
CLASS="glossdef"
><P
CLASS="para"
>One of the first versions of UNIX to run on IBM PCs, and one of the
few that will run on 80286 systems. XENIX descends from Version&nbsp;7
UNIX, a version developed by AT&amp;T in the late 1970s. It has many
resemblances to BSD UNIX. Over time, XENIX has been rewritten as a
variant of System&nbsp;V.2.</P
></DD
><DT
CLASS="glossterm"
><A
CLASS="glossterm"
NAME="GLOSS-ZOMBIES"
>zombies</A
></DT
><DD
CLASS="glossdef"
><P
CLASS="para"
>Dead processes that have not yet been deleted from the process table.
Zombies normally disappear almost immediately. However, at times it
is impossible to delete a zombie from the process table, so it remains
there (and in your <EM
CLASS="emphasis"
>ps</EM
> output) until you reboot. Aside from
their slot in the process table, zombies don't require any of the
system's resources.
<EM
CLASS="emphasis"
>See also</EM
> article
<A
CLASS="xref"
HREF="ch38_16.htm"
TITLE="Why You Can't Kill a Zombie "
>38.16</A
>.</P
></DD
><DIV
CLASS="docinfo"
><P
CLASS="DOCINFO"
>- <SPAN
CLASS="authorinitials"
>JP</SPAN
>, <SPAN
CLASS="authorinitials"
>ML</SPAN
></P
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