This file is of historic interest. For recent changes in both ksh 93u+m and
the accompanying libraries, see the file NEWS in the top-level directory.
____
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
associative 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 a 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. ${name//pattern/string} expands to the value of name with
each occurrence of pattern replaced by string.
With aggregates (@ or *) this operation is applied to each.
d. The name space for variables has been extended. The character '.'
can be used at the beginning of a name, and to separate identifiers
within a name. However, to create a name of the form, foo.bar,
the variable foo must exist. The namespace starting with .sh
is reserved for shell implementation variables. Exported
variables cannot contain a '.'.
e. Compound assignments. The assignment syntax, varname=value,
has been extended to allow assignments of the form
varname=(assignment_list). As elsewhere in the shell
spaces or tabs are optional around the parentheses, and
no space is permitted between the varname and the =. The
assignment_list can be one of the following:
1. A list of words. In this case each word is expanded as
in a for list and the resulting items become elements
of the indexed array varname.
2. A list of subscript assignments in the form
[subscript]=value. In this, these elements become
elements of the associative array varname.
3. A list of assignments; simple or compound. In this
case, each assignment is made to varname.name, where
name is the name of the enclosed assignment.
4. Assignments in the form of readonly or typeset
statements. In this case each assignment is made as
in 3 above, and the attributes are given to the
corresponding variable.
In case 3 and 4 above, the value of "$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
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 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 to
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 only causes 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. There 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.
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