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207 lines
6.8 KiB
HTML
207 lines
6.8 KiB
HTML
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<TITLE> www/ksh/features.mm mm document </TITLE>
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<TABLE border=0 align=center width=96%>
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<!--INDEX--><!--/INDEX-->
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<P>
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<P><CENTER><FONT color=red><FONT face=courier><H3><A name="ksh features">ksh features</A></H3></FONT></FONT></CENTER>
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KSH-93 is the most recent version of the KornShell Language described in
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<EM>The KornShell Command and Programming Language</EM>,
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by Morris Bolsky and David Korn of AT&T Research (nee Bell Laboratories).
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The KornShell is a shell programming language,
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which is upward compatible with
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<EM>sh</EM>
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(the Bourne Shell),
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and is intended to conform to the IEEE P1003.2/ISO 9945.2 Shell and
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Utilities standard.
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KSH-93 provides an enhanced programming environment in
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addition to the major command-entry features of the BSD
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shell
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<EM>csh</EM>.
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With KSH-93, medium-sized programming tasks can be
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performed at shell-level without a significant loss in performance.
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In addition,
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<EM>sh</EM>
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scripts can be run on KSH-93 without modification.
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<P>
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The code should conform to the IEEE POSIX 1003.1 standard and to the
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proposed ANSI-C standard so that it should be portable to all
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such systems.
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Like the previous version, KSH-88,
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it is designed to accept eight bit character sets
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transparently, thereby making it internationally compatible.
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It can support multi-byte characters sets with some characteristics
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of the character set given at run time.
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<P>
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KSH-93 provides the following features, many of which were also inherent
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in KSH-88:
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<P>
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<H4><A name="Enhanced Command Re-entry Capability">Enhanced Command Re-entry Capability</A></H4>
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The KSH-93 history
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function records commands entered at any shell level and stores
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them, up to a user-specified limit, even after you log off.
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This allows you to re-enter long commands with a few keystrokes
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- even those commands you entered yesterday.
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The history file allows for eight bit characters in
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commands and supports essentially unlimited size histories.
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<P>
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<H4><A name="In-line Editing">In-line Editing</A></H4>
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In
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<EM>sh</EM>
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the only way to fix mistyped
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commands is to backspace or retype the line.
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KSH-93 allows you
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to edit a command line using a choice of EMACS-TC or
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<EM>vi</EM>
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functions.
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You can use the in-line editors to complete filenames as
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you type them.
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You may also use this editing feature when entering
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command lines from your history file.
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A user can capture keystrokes and rebind keys to customize the
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editing interface.
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<P>
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<H4><A name="Extended I/O Capabilities">Extended I/O Capabilities</A></H4>
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KSH-93 provides several I/O
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capabilities not available in
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<EM>sh</EM>,
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including the ability to:
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<UL type=square>
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<LI>
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specify a file descriptor for input and output
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<LI>
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start up and run co-processes
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<LI>
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produce a prompt at the terminal before a read
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<LI>
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easily format and interpret responses to a menu
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<LI>
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echo lines exactly as output without escape processing
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<LI>
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format output using printf formats.
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<LI>
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read and echo lines ending in "\e".
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</UL>
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<P>
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<H4><A name="Improved performance">Improved performance</A></H4>
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KSH-93 executes many scripts faster
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than the System V Bourne shell.
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A major reason for this is
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that many of the standard utilities are built-in.
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To reduce the time to initiate a command, KSH-93 allows
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commands to be added as built-ins at run time
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on systems that support dynamic loading such as System V Release 4.
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<P>
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<H4><A name="Arithmetic">Arithmetic</A></H4>
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KSH-93 allows you to do integer arithmetic in any
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base from two to sixty-four.
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You can also do double
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precision floating point arithmetic.
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Almost the complete set of C language operators are available
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with the same syntax and precedence.
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Arithmetic expressions can be used to as an argument expansion
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or as a separate command.
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In addition there is an arithmetic for command that works
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like the for statement in C.
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<P>
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<H4><A name="Arrays">Arrays</A></H4>
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KSH-93 supports both indexed and associative arrays.
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The subscript for an indexed array is an arithmetic expression,
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whereas, the subscript for an associative array is a string.
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<P>
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<H4><A name="Functions and Aliases">Functions and Aliases</A></H4>
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Two mechanisms - functions and
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aliases - can be used to assign a user-selected identifier to
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an existing command or shell script.
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Functions allow local variables and provide scoping
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for exception handling.
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Functions can be searched for and loaded on first reference the
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way scripts are.
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<P>
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<H4><A name="Substring Capabilities">Substring Capabilities</A></H4>
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KSH-93 allows you to create a
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substring of any given string either by specifying the starting
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offset and length, or by stripping off leading
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or trailing substrings during parameter substitution.
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You can also specify attributes, such as upper and lower case,
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field width, and justification to shell variables.
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<P>
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<H4><A name="Enhanced pattern matching capabilities">Enhanced pattern matching capabilities</A></H4>
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KSH-93 allows you to specify
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regular expressions for file and string matches.
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<P>
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<H4><A name="Improved debugging">Improved debugging</A></H4>
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KSH-93 can generate line numbers on execution traces.
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Also, I/O redirections are now traced.
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There is a DEBUG trap that gets evaluated after each command
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so that errors can be localized.
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<P>
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<H4><A name="Job Control">Job Control</A></H4>
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On systems that support job control, including
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System V Release 4, KSH-93
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provides a job-control mechanism almost identical to that of
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the BSD "csh", version 4.1.
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This feature allows you
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to stop and restart programs, and to move programs between the
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foreground and the background.
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<P>
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<H4><A name="Added security">Added security</A></H4>
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KSH-93 can execute scripts which do not have read permission
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and scripts which have the setuid and/or setgid set when
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invoked by name, rather than as an argument to the shell.
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It is possible to log or control the execution of setuid and/or
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setgid scripts.
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The noclobber option prevents you from accidentally erasing
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a file by redirecting to an existing file.
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<P>
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<H4><A name="Documentation">Documentation</A></H4>
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Documentation for KSH-93 consists of an
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<EM>Introduction to KSH-93,</EM>
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<EM>Compatibility with the Bourne Shell</EM>,
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a manual page and a
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README file.
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In addition, the
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<EM>New KornShell Command and Programming Language</EM>
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book is available from Prentice Hall.
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<P>
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<HR>
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<TABLE border=0 align=center width=96%>
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<TR>
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<TD align=left></TD>
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<TD align=center></TD>
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<TD align=right>March 13, 2012</TD>
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</TR>
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</TABLE>
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<P>
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</TD></TR></TBODY></TABLE>
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</BODY>
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</HTML>
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