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188 lines
9.5 KiB
Markdown
188 lines
9.5 KiB
Markdown
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# KornShell 93u+m
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This repository is used to develop bugfixes
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to the last stable release (93u+ 2012-08-01) of
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[ksh93](http://www.kornshell.com/),
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formerly developed by AT&T Software Technology (AST).
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The sources in this repository were forked from the
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Github [AST repository](https://github.com/att/ast)
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which is no longer under active development.
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To see what's fixed, see [NEWS](https://github.com/ksh93/ksh/blame/master/NEWS)
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and click on commit messages for full details.
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To see what's left to fix, see [TODO](./TODO).
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## Policy
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1. No new features; bug fixes only (but see items 3 and 4).
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Feature development is for a future separate branch.
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2. No major rewrites. No refactoring code that is not fully understood.
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3. No changes in documented behaviour, except if required for compliance with the
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[POSIX shell language standard](https://pubs.opengroup.org/onlinepubs/9699919799/utilities/contents.html)
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which David Korn [intended](http://www.kornshell.com/info/) for ksh to follow.
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4. No 100% bug compatibility. Broken and undocumented behaviour gets fixed.
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5. No bureaucracy, no formalities. Just fix it, or report it: create issues,
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send pull requests. Every interested party is invited to contribute.
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6. To help increase everyone's understanding of this code base, fixes and
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significant changes should be fully documented in commit messages.
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## Why?
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Between 2017 and 2020 there was an ultimately unsuccessful
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[attempt](https://github.com/att/ast/tree/2020.0.1)
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to breathe new life into the KornShell by extensively refactoring the last
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unstable AST beta version (93v-).
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While that ksh2020 branch is now abandoned and still has many critical bugs,
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it also had a lot of bugs fixed. More importantly, the AST issue tracker
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now contains a lot of documentation on how to fix those bugs, which made
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it possible to backport many of them to the last stable release instead.
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This ksh 93u+m reboot now incorporates many of these bugfixes, as well as
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many patches from Red Hat, Solaris, as well as new fixes from the community.
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Though there are many bugs left to fix, we are confident at this point that
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93u+m is already the least buggy branch of ksh93 ever released.
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## Build
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After downloading a release or cloning the ksh git repository, cd to the top
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directory of it and run:
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```sh
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bin/package make
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```
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If you have trouble or want to tune the binaries, you may pass additional
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compiler and linker flags. It is usually best to export these as environment
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variables *before* running `bin/package` as they could change the name of
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the build subdirectory of the `arch` directory, so exporting them is a
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convenient way to keep them consistent between build and test commands.
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**Note that this system uses `CCFLAGS` instead of the usual `CFLAGS`.**
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An example that makes Solaris Studio cc produce a 64-bit binary:
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```sh
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export CCFLAGS="-xc99 -m64 -O2" LDFLAGS="-m64"
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bin/package make
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```
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Alternatively you can append these to the command, and they will only be
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used for that command. You can also specify an alternative shell in which
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to run the build scripts this way. For example:
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```sh
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bin/package make SHELL=/bin/bash CCFLAGS="-O2 -I/opt/local/include" LDFLAGS="-L/opt/local/lib"
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```
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For more information run
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```sh
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bin/package help
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```
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Many other commands in this repo self-document via the `--help`, `--man` and
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`--html` options; those that do have no separate manual page.
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## Test
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After compiling, you can run the regression tests.
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Start by reading the information printed by:
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```sh
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bin/shtests --man
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```
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## What is ksh93?
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The following is the official AT&T description from 1993 that came with the
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ast-open distribution. The text is original, but hyperlinks were added here.
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----
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KSH-93 is the most recent version of the KornShell Language described in
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"The KornShell Command and Programming Language," by Morris Bolsky and David
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Korn of AT&T Bell Laboratories, ISBN 0-13-182700-6. The KornShell is a shell
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programming language, which is upward compatible with "sh" (the Bourne
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Shell), and is intended to conform to the IEEE P1003.2/ISO 9945.2
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[Shell and Utilities standard](https://pubs.opengroup.org/onlinepubs/9699919799/utilities/contents.html).
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KSH-93 provides an enhanced programming environment in addition to the major
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command-entry features of the BSD shell "csh". With KSH-93, medium-sized
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programming tasks can be performed at shell-level without a significant loss
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in performance. In addition, "sh" scripts can be run on KSH-93 without
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modification.
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The code should conform to the
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[IEEE POSIX 1003.1 standard](http://www.opengroup.org/austin/papers/posix_faq.html)
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and to the proposed ANSI-C standard so that it should be portable to all
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such systems. Like the previous version, KSH-88, it is designed to accept
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eight bit character sets transparently, thereby making it internationally
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compatible. It can support multi-byte characters sets with some
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characteristics of the character set given at run time.
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KSH-93 provides the following features, many of which were also inherent in
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KSH-88:
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* Enhanced Command Re-entry Capability: The KSH-93 history function records
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commands entered at any shell level and stores them, up to a
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user-specified limit, even after you log off. This allows you to re-enter
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long commands with a few keystrokes - even those commands you entered
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yesterday. The history file allows for eight bit characters in commands
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and supports essentially unlimited size histories.
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* In-line Editing: In "sh", the only way to fix mistyped commands is to
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backspace or retype the line. KSH-93 allows you to edit a command line
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using a choice of EMACS-TC or "vi" functions. You can use the in-line
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editors to complete filenames as you type them. You may also use this
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editing feature when entering command lines from your history file. A user
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can capture keystrokes and rebind keys to customize the editing interface.
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* Extended I/O Capabilities: KSH-93 provides several I/O capabilities not
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available in "sh", including the ability to:
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* specify a file descriptor for input and output
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* start up and run co-processes
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* produce a prompt at the terminal before a read
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* easily format and interpret responses to a menu
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* echo lines exactly as output without escape processing
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* format output using printf formats.
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* read and echo lines ending in "\\".
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* Improved performance: KSH-93 executes many scripts faster than the System
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V Bourne shell. A major reason for this is that many of the standard
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utilities are built-in. To reduce the time to initiate a command, KSH-93
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allows commands to be added as built-ins at run time on systems that
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support dynamic loading such as System V Release 4.
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* Arithmetic: KSH-93 allows you to do integer arithmetic in any base from
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two to sixty-four. You can also do double precision floating point
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arithmetic. Almost the complete set of C language operators are available
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with the same syntax and precedence. Arithmetic expressions can be used to
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as an argument expansion or as a separate command. In addition there is an
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arithmetic for command that works like the for statement in C.
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* Arrays: KSH-93 supports both indexed and associative arrays. The subscript
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for an indexed array is an arithmetic expression, whereas, the subscript
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for an associative array is a string.
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* Shell Functions and Aliases: Two mechanisms - functions and aliases - can
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be used to assign a user-selected identifier to an existing command or
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shell script. Functions allow local variables and provide scoping for
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exception handling. Functions can be searched for and loaded on first
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reference the way scripts are.
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* Substring Capabilities: KSH-93 allows you to create a substring of any
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given string either by specifying the starting offset and length, or by
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stripping off leading or trailing substrings during parameter
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substitution. You can also specify attributes, such as upper and lower
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case, field width, and justification to shell variables.
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* More pattern matching capabilities: KSH-93 allows you to specify extended
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regular expressions for file and string matches.
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* KSH-93 uses a hierarchal name space for variables. Compound variables can
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be defined and variables can be passed by reference. In addition, each
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variable can have one or more disciplines associated with it to intercept
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assignments and references.
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* Improved debugging: KSH-93 can generate line numbers on execution traces.
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Also, I/O redirections are now traced. There is a DEBUG trap that gets
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evaluated before each command so that errors can be localized.
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* Job Control: On systems that support job control, including System V
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Release 4, KSH-93 provides a job-control mechanism almost identical to
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that of the BSD "csh", version 4.1. This feature allows you to stop and
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restart programs, and to move programs between the foreground and the
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background.
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* Added security: KSH-93 can execute scripts which do not have read
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permission 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. It is possible
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to log or control the execution of setuid and/or setgid scripts. The
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noclobber option prevents you from accidentally erasing a file by
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redirecting to an existing file.
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* KSH-93 can be extended by adding built-in commands at run time. In
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addition, KSH-93 can be used as a library that can be embedded into an
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application to allow scripting.
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Documentation for KSH-93 consists of an "Introduction to KSH-93",
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"Compatibility with the Bourne Shell" and a manual page and a README file.
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In addition, the "New KornShell Command and Programming Language" book is
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available from Prentice Hall.
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