8322 nl: misleading-indentation

[unleashed/tickless.git] / usr / src / lib / libshell / common / RELEASE88

This is a list of changes that have been made since the 11/16/88 version
of ksh.

1.  New features in 12/28/93
    a.  Associative arrays.  The new version of ksh supports both
        associate arrays and the older indexed arrays with the same
        array syntax.  A new -A option of typeset is used to declare
        an array to be associative.  As with indexed arrays, $name is
        equivalent to ${name[0]}.  The prefix operator ! was added
        to the parameter expansion syntax to expand to the list of
        indices.  For example, ${!name[@]} expands to the list of array
        indices for variable name.

    b.  Several additions have been made to shell arithmetic:
        1.  The shell now performs floating point arithmetic.  The
            typeset options -F and -E have been added for floating
            point and scientific notation respectively.
        2.  The prefix and postfix ++ and -- operators.
        3.  The comma and ?: operators.
        4.  The math library functions.
        5.  An arithmetic for statement of the form
                for ((expr1; expr2; expr3))
                do      ...
                done
        6.  Integer arithmetic extended up to base 64.

    c.  Some additions to the macro expansion syntax have been made
        to specify substrings and sub-arrays:
        1.  ${name:expr} expands to the substring of ${name} starting at
            the character position defined by arithmetic expression expr.
        2.  ${name:expr1:expr2} expands to the substring of ${name} starting
            at expr1 and consisting of at most expr2 characters.
        3.  ${name[@]:expr} expands to the values of ${name[@]} starting at
            the element defined by arithmetic expression expr.
        4.  ${name[@]:expr1:expr2} expands to at most expr2 values of
            ${name} starting at expr1.
        5.  ${@:expr} expands the positional parameters starting at expr.
        6.  ${@:expr1:expr2} expands to at most expr2 positional parameters
            starting at expr1.
        7.  ${!name} expands to the name of the variable named by name.
            It will expand to name unless name is reference variable.
        8.  ${!name[sub]} expands to the name of the subscript of the
            given variable.  If sub is @ or * the list of subscripts
            is generated.
        9.  ${!prefix*} and ${!prefix@} expand to the list of variable
            names beginning with prefix.
        10. The substring operators, # and % can be now be applied
            with aggregates (@ or *) and are applied to each.
        11. ${name/pattern/string} expands to the value of name with
            the first occurrence of pattern replaced by string.
            With aggregates (@ or *) this operation is applied to each.
        12. ${name/#pattern/string} Same as above but the pattern
            to be replaced must match at the beginning.
        13. ${name/%pattern/string} Same as above but the pattern
            to be replaced must match at the end.
        14. ${name//pattern/string} expands to the value of name with
            the each occurrence of pattern replaced by string.
            With aggregates (@ or *) this operation is applied to each.

    d.  The name space for variables has been extended.  The character '.'
        can be used at the beginning of a name, and to separate identifiers
        within a name.  However, to create a name of the form, foo.bar,
        the variable foo must exist. The namespace starting with .sh
        is reserved for shell implementation variables.  Exported
        variable cannot contain a '.'.

    e.  Compound assignments.  The assignment syntax, varname=value,
        has been extended to allow assignments of the form
        varname=(assignment_list).  As elsewhere in the shell
        spaces or tabs are optional around the parentheses, and
        no space is permitted between the varname and the =.  The
        assignment_list can be one of the following:
        1.  A list of words.  In this case each word is expanded as
            in a for list and the resulting items become elements
            of the indexed array varname. 
        2.  A list of subscript assignments in the form
            [subscript]=value.  In this, these elements become 
            elements of the associative array varname. 
        3.  A list of assignments; simple or compound.  In this
            case, each assignment is made to varname.name, where
            name is the name of the enclosed assignment.
        4.  Assignments in the form of readonly or typeset
            statements.  In this case each assignment is made as
            in 3 above, and the attributes are given to the
            corresponding variable.
        In case 3 and 4 above, the value of "$varname" after
        the above assignment is (assignment_list), where the
        assignment_list produced would reproduce all of the
        variables under varname.*.

    f.  Function names of the form variable.action (called discipline
        functions) can be defined where variable is any valid variable
        name and action is get, set, or unset.  The function variable.get
        is invoked each time the variable is referenced.  The set
        discipline is invoked each time the variable is assigned to.
        The unset discipline is invoked when a variable is unset.
        The new variables .sh.name, .sh.subscript, and .sh.value are
        defined inside the function body.  Other shell extensions
        may have their own set of discipline functions.

    g.  The compound command !, which negates the return value of the
        following pipeline, has been added.

    h.  On systems that support dynamic loading with dlopen(), it is
        now possible to add built-in commands at runtime with the
        a builtin command named builtin. 

    i.  The following builtins have been added:
        1.  command name [ ... ]
        2.  sleep [decimal-seconds]
        3.  builtin [-ds] [-f file] [name...]
        4.  getconf name [pathname]
        5.  disown [job...]

    j.  An addition format for literal strings, $'....' can
        be used where ever literal strings are valid.  The string
        inside the single quotes will be converted using the ANSI-C
        escape conventions.  Additionally, the escape sequence \E
        expands to the escape character (default \033) whenever ANSI-C
        escape sequences are recognized.

    k.  A typeset -n option has been added which causes the value of a
        variable to be treated as a reference to another variable so that
        variables can be indirectly named.  For example, if $1 contains
        the name of a variable, then typeset -n foo=$1 causes the variable
        foo to be synonymous with the variable whose name is $1.  A builtin
        alias, nameref='typeset -n' has been added to aid mnemonics.
        Reference names cannot contain a '.'.  Whenever that portion of
        a variable up to the first '.' matches a reference name, the
        reference value is substituted.  For example, with nameref foo=.top,
        then ${foo.bar} is equivalent to ${.top.bar}.  When used as the
        index of a for or select loop, each assignment causes a
        new name reference to occur.
        
    l.  The KEYBD trap has been added which is triggered when a key
        or escape sequence is typed while reading from the keyboard
        in an edit mode.  This, combined with some new variables
        makes it possible to program your key bindings in ksh.

    m.  New variables have been added:
        1.  FIGNORE defines a set of file names to be ignored in each
            directory when performing pathname expansion, replacing
            the rule that requires that a leading . be matched explicitly.
        2.  Variable sh.edchar contains the value of the keyboard character
            that has been entered when processing a KEYBD trap.  If the value
            is changed as part of the trap action, then the new value replaces
            the key or keys that caused the trap.
        3.  Variable sh.edcol is set to the character position of the cursor
            within the input buffer during a KEYBD trap.
        4.  Variable sh.edmode is set to the escape character when in vi
            insert mode.
        5.  Variable sh.edtext is set to the contents of the input buffer
            during a KEYBD trap.
        6.  HISTEDIT is checked before FCEDIT.  FCEDIT is obsolete.
        7.  HISTCMD is the number of the current command in the history
            file.
        8.  Variable .sh.version is set to the version string for
            this shell.
        9.  Variable .sh.name is set to the name of the variable
            that that was referenced or assigned to when executing a get
            or set discipline function.
        10. Variable .sh.subscript is set to the subscript for the variable
            that was referenced or assign to when executing a get or
            set discipline function.
        11. Variable .sh.value is set to the new value for the variable
            that was assigned to when executing the set discipline function.

    n.  New invocation and set -o options have been added:
        1.  set -o notify (or set -b) causes background completion messages
            to be displayed as soon as the job completes.
        2.  There is a compile time option named KIA which enables
            creation of a relational database for commands, variables
            and functions defined and referenced by a script.  The
            option -I <filename>, causes the database to be generated
            in <filename>.  The database format can be queried via
            the cql command.
    o.  ksh93 can read and evaluate pre-compiled scripts generated by
        a separate program called shcomp.
    p.  More work on internationalization has been added:
        1.  The decimal point character is processed per locale
        2.  A $  can be placed in front of each string to indicate
            that the string needs translation but is otherwise ignored.
            This means that if a message catalog of all $"..." strings
            is generated, then a program such as print $"hello world"
            could display "bonjour monde" in the french locale.
    q.  Backreferences have been added to pattern matching.  The sequence
        \d, where d is a digit from 1-9, matches the same string as
        the d-th previous parenthesis group.  Backreferences
        can be used within patterns, and within replacement strings
        with any of the ${name/...} operators.

2.  Changes made in 12/28/93
    a.  The output format of many commands has changed as follows:
        1.  System error messages are displayed whenever a failure
            is caused by a system call.
        2.  The exit status has changed in many cases:
            a.  USAGE messages cause an exit status of 2.
            b.  Commands not found cause exit - 127.
            c.  Command found, but not executable - 126.
            d.  Terminated because of signal -  256+sig
        3.  The output of values from built-ins that contain special
            characters are quoted in a manner that then can be re-input.
        4.  The trace output puts quotes around the output so that it
            can be reused as input.
        5.  The output for trap is in a format that can be reinput the
            the shell to restore the traps.
        6.  kill -l lists the signal names without numbers as
            required by the POSIX standard.

    b.  The following changes have been made to shell functions:
        1.  The semantics of functions declared with name() has changed
            to conform with the IEEE-POSIX 1003.2 standard.  In particular,
            these functions are executed in a dot script environment rather
            than a separated function environment so that there are no
            local variables and no scoping for traps.
        2.  Functions declared as function name, preserve the old ksh
            semantics can be also used as the first argument to the dot (.)
            command to have them executed in a dot script environment.
        
    c.  The command search rules have changed as follows:
        1.  Special built-ins (those with a dagger in front of them) are
            executed first.
        2.  Functions are executed next.
        3.  Other built-ins that do not require an executable version
            (for example cd and read) come next.
        4.  If the command name contains a slash, the pathname corresponding
            to the command name is executed.
        5.  If name corresponds to a previously encountered pathname
            on the PATH variable, the corresponding command is executed.
        6.  If the command name does not contain a slash, then the PATH
            variable is used to find an executable by that name.  If
            the directory that the command is found is also contained in
            the FPATH variable, then the command treated as a function.
            If the shell has a built-in version of the command corresponding
            to this command, then the built-in version of this command
            is executed.  Otherwise, the shell remembers that pathname
            corresponding to this command name and executes this pathname.
        7.  If the name is not found on PATH, then the directories in
            FPATH are searched.  If found, then the command is executed
            as a function.

    d.  Built-in commands options now conform to the IEEE-POSIX 1003.2
        conventions with some additions.  In particular,
                name -?
        will now print a Usage line for name, except for true, false,
        colon, login, newgrp, echo, [, and command.

    e.  Tilde expansion is now performed as part of the word expansions.
        The effect of this is that if word begins with ~ in ${name op word},
        it will be expanded unless escaped.

    f.  Pathname expansion is no longer performed on redirection words
        unless the shell is interactive.

    g.  Changes to shell and options:
        1.  The -n option has been enhanced to produce more warning and
            portability messages.
        2.  The -C option is equivalent to -o noclobber.  Files are
            created with O_EXCL when -C is on.

    h.  The following changes have been made to [[...]]:
        1.  A string by itself is equivalent to -n string.
        2.  -e has been added as equivalent to -a.
        3.  == has been added as equivalent =.
        4.  -a and = are now considered obsolete.
        5.  Arithmetic comparisons are now considered obsolete.

    i.  kill has been changed as follows:
        1.  Signal names can be upper case or lower case.
        2.  Numerical arguments to kill -l cause the given signal names to
            be displayed.
        3.  String arguments to kill -l cause the given signal numbers to
            be displayed.
        4.  Synopsis changed for getopts conformance.

    j.  print has a -f format option which is equivalent to
        the IEEE POSIX printf.  Both print -f format, and
        printf have the following extensions from IEEE POSIX:
        1.  Floating point formats are supported.
        2.  Size and precision specifications can be *.
        3.  The %d option can take an argument after precision to
            specify the base that the number will be displayed.
        4.  A %q format can be used to output a string quoted so
            that it can be re-input to the shell.
        5.  A %P format can be used to output the shell pattern which
            corresponds to the give extended regular expression.
        6.  For numerical fields, the arguments can be arithmetic
            expressions which will be evaluated.
        7.  The %n format works as described in ANSI-C.

    k.  The following changes have been made to fc:
        1.  It has been renamed hist.  fc is now a predefined alias.
        2.  hist uses ${HISTEDIT:-$FCEDIT}.  FCEDIT is obsolete.
        3.  A new -s option is equivalent to the obsolete -e -.
        4.  If the first argument refers to a command earlier than the
            first accessible command, it now implies the first accessible
            command, so that hist -l 1 lists all accessible history commands.

    l.  The dot command (.) has changed as follows:
        1.  The argument can be the name of a function declared as
            function name.  The function will execute without creating a
            new scope.
        2.  If there are arguments to the given script or function,
            the positional parameters are restored to their original
            value when . completes.

    m.  The read built-in has been changed as follows:
        1.  A -A option to read has been added to allow the fields to be
            read into an indexed array.
        2.  A -t n option has been added which causes read to
            timeout after n seconds when reading from a slow device.
        3.  A -d char option has been added which causes the read
            to terminate at char rather than at new-line.
        
    n.  The trap command has been changed as follows:
        1.  Trap names can be either upper case or lower case.
        2.  Trap -p cause only the specified trap values to be displayed. 
        3.  The value of trap in a subshell will be the value in the parent
            shell until a call to trap which changes the trap settings has
            been made.  Thus, savetraps=$(trap) works as required by the
            POSIX standard.

    o.  The exec command has been extended as follows:
        1.  The -c option clears the environment first.
        2.  The -a name option sets argv[0] to name for the program.

    p.  true and false are built-ins, not aliases to built-ins.

    q.  test has been modified to conform to the IEEE-POSIX 1003.2
        standard when there are three or less arguments.

    r.  umask -S option displays the mask in a symbolic format.

    s.  wait now returns the correct exit status of any previous
        background job that has not been waited for, not just
        the most recent one.

    t.  The whence built-in has an option -a which causes all
        uses for the given command name to be reported.

    u.  unalias has -a option to clear all the aliases.
 
    v.  The times built-in command has been removed.  The time
        reserved word, without a command, gives time cumulative
        time for the shell and its children.  A built-in alias
        for times should enable scripts using times to continue
        to run.

    w.  Command substitution and arithmetic substitution will now be
        performed for PS1, ENV, and PS4 evaluation in addition to
        parameter expansion.

    x.  The SECONDS variable now displays elapsed time in floating
        point seconds with 3 places after the decimal point by
        default.

    y.  The getopts built-in now handles the complete libast optget
        functionality.  If any errors have occurred with getopts
        when it has reached the end of arguments, then the Usage
        message will be generated from the option string and the
        exit status from getopts will be 2 rather than 1.  The
        usage message will be stored in the OPTARG variable if
        the option string contains a leading colon; otherwise
        it will be printed on standard error automatically.

    z.  THE ENV file is only processed for interactive shell
        invocations.  In addition, the -x attributes for
        aliases and functions is ignored.

    aa. The built-in edit modes have been changed as follows:
        1. The pathname completion and pathname listing options
           now perform command completion and command listing
           when applied to a word in the command position.
        2. In emacs mode ^N as the first related command after
           the prompt will move to the next command relative to the
           last known history position.
        3. In emacs mode, successive kill and delete commands will
           accumulate their data in the kill buffer, by appending or
           prepending as appropriate.  This mode will be reset by any
           command not adding something to the kill buffer.
        4. The control-T of emacs mode has been changed to behave like
           control-T in gnu-emacs.
    bb. The TMOUT variable also sets a limit for select timeouts
        and default timeouts for read.


4.  The source code has undergone significant modification.
    a.  Much of the code has been rewritten,  In many cases this has
        resulted in significant performance improvement.

    b.  The code is organized differently.  See the README files
        for more details.

    c.  Most configuration parameters now get generated using
        the FEATURE mechanism of nmake.  Other options are set
        in the OPTIONS file.

    c.  The are several new compile time options. See the README
        file for details.  Some of the old ones have been removed.

    d.  The install script is a Mamfile that is generated by
        nmake and processed by a script that comes with the
        distribution.

    e.  There are far fewer global names.  This should make it
        must easier to add built-in commands without worrying
        about conflicts.
                
    f.  The code uses the sfio library which makes it possible
        to mix with stdio.

    g.  The code is written in ANSI C with full prototypes.
        The code is based on the IEEE POSIX 1003.1 standard.
        The code can be compiled with K&R C and with C++ by
        using the ANSI cpp that comes with nmake or running
        the code through the proto filter before pre-processing.
        This happens automatically with our shipping system.

    h.  There is a programming interface for capturing references
        and assignment to shell variables.  It is also possible
        to intercept variable creation and supply the array processing
        function for that variable.  See nval.3 for a description.