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66e1d44642
This commit fixes 'command -x' to adapt to OS limitations with
regards to data alignment in the arguments list. A feature test is
added that detects if the OS aligns the argument on 32-bit or
64-bit boundaries or not at all, allowing 'command -x' to avoid
E2BIG errors while maximising efficiency.
Also, as of now, 'command -x' is a way to bypass built-ins and
run/query an external command. Built-ins do not limit the length of
their argument list, so '-x' never made sense to use for them. And
because '-x' hangs on Linux and macOS on every ksh93 release
version to date (see acf84e96), few use it, so there is little
reason not to make this change.
Finally, this fixes a longstanding bug that caused the minimum exit
status of 'command -x' to be 1 if a command with many arguments was
divided into several command invocations. This is done by replacing
broken flaggery with a new SH_XARG state flag bit.
src/cmd/ksh93/features/externs:
- Add new C feature test detecting byte alignment in args list.
The test writes a #define ARG_ALIGN_BYTES with the amount of
bytes the OS aligns arguments to, or zero for no alignment.
src/cmd/ksh93/include/defs.h:
- Add new SH_XARG state bit indicating 'command -x' is active.
src/cmd/ksh93/sh/path.c: path_xargs():
- Leave extra 2k in the args buffer instead of 1k, just to be sure;
some commands add large environment variables these days.
- Fix a bug in subtracting the length of existing arguments and
environment variables. 'size -= strlen(cp)-1;' subtracts one less
than the size of cp, which makes no sense; what is necessary is
to substract the length plus one to account for the terminating
zero byte, i.e.: 'size -= strlen(cp)+1'.
- Use the ARG_ALIGN_BYTES feature test result to match the OS's
data alignment requirements.
- path_spawn(): E2BIG: Change to checking SH_XARG state bit.
src/cmd/ksh93/bltins/whence.c: b_command():
- Allow combining -x with -p, -v and -V with the expected results
by setting P_FLAG to act like 'whence -p'. E.g., as of now,
command -xv printf
is equivalent to
whence -p printf
but note that 'whence' has no equivalent of 'command -pvx printf'
which searches $(getconf PATH) for a command.
- When -x will run a command, now set the new SH_XARG state flag.
src/cmd/ksh93/sh/xec.c: sh_exec():
- Change to using the new SH_XARG state bit.
- Skip the check for built-ins if SH_XARG is active, so that
'command -x' now always runs an external command.
src/lib/libcmd/date.c, src/lib/libcmd/uname.c:
- These path-bound builtins sometimes need to run the external
system command by the same name, but they did that by hardcoding
an unportable direct path. Now that 'command -x' runs an external
command, change this to using 'command -px' to guarantee using
the known-good external system utility in the default PATH.
- In date.c, fix the format string passed to 'command -px date'
when setting the date; it was only compatible with BSD systems.
Use the POSIX variant on non-BSD systems.
224 lines
9.9 KiB
Text
224 lines
9.9 KiB
Text
ksh 93u+m vs. ksh 93u+
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The following is a list of changes between ksh 93u+ 2012-08-01 and the new
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ksh 93u+m reboot that could cause incompatibilities in rare corner cases.
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Fixes of clear bugs in ksh 93u+ are not included here, even though any bugfix
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could potentially cause an incompatibility in a script that relies on the bug.
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For more details, see the NEWS file and for complete details, see the git log.
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0. A new '-o posix' shell option has been added to ksh 93u+m that makes
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the ksh language more compatible with other shells by following the
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POSIX standard more closely. See the manual page for details. It is
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enabled by default if ksh is invoked as sh.
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1. Bytecode compiled by shcomp 93u+m will not run on older ksh versions.
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(However, bytecode compiled by older shcomp will run on ksh 93u+m.)
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2. File name generation (a.k.a. pathname expansion, a.k.a. globbing) now
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never matches the special navigational names '.' (current directory)
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and '..' (parent directory). This change makes a pattern like .*
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useful; it now matches all hidden 'dotfiles' in the current directory.
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3. The bash-style &>foo redirection operator (shorthand for >foo 2>&1) can
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now always be used if -o posix is off, and not only in profile scripts.
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4. Most predefined aliases have been converted to regular built-in
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commands that work the same way. 'unalias' no longer removes these.
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To remove a built-in command, use 'builtin -d'. The 'history' and 'r'
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predefined aliases remain, but are now only set on interactive shells.
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There are some minor changes in behavior in some former aliases:
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- 'redirect' now checks if all arguments are valid redirections
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before performing them. If an error occurs, it issues an error
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message instead of terminating the shell.
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- 'suspend' now refuses to suspend a login shell, as there is probably
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no parent shell to return to and the login session would freeze.
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- 'times' now gives high precision output in a POSIX compliant format.
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5. 'command' no longer expands aliases in its first argument, as this is
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no longer required after change 3 above. In the unlikely event that you
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still need this behavior, you can set:
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alias command='command '
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6. The undocumented 'login' and 'newgrp' builtin commands have been
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removed. These replaced your shell session with the external commands
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by the same name, as in 'exec'. If an error occurred (e.g. due to a
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typo), you would end up immediately logged out. If you do want this
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behavior, you can restore it by setting:
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alias login='exec login'
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alias newgrp='exec newgrp'
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7. 'case' no longer retries to match patterns as literal strings if they
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fail to match as patterns. This undocumented behaviour broke validation
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use cases that are expected to work. For example:
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n='[0-9]'
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case $n in
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[0-9]) echo "$n is a number" ;;
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esac
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would output "[0-9] is a number". In the unlikely event that a script
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does rely on this behavior, it can be fixed like this:
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case $n in
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[0-9] | "[0-9]")
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echo "$n is a number or the number pattern" ;;
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esac
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8. If 'set -u'/'set -o nounset' is active, then the shell now errors out
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if a nonexistent positional parameter such as $1, $2, ... is accessed.
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(This does *not* apply to "$@" and "$*".)
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9. If 'set -u'/'set -o nounset' is active, then the shell now errors out
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if $! is accessed before the shell has launched any background process.
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10. The 'print', 'printf' and 'echo' builtin commands now return a nonzero
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exit status if an input/output error occurs.
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11. Four obsolete date format specifiers for 'printf %(format)T' were
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changed to make them compatible with modern date(1) commands:
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- %k and %l now return a blank-padded hour (24-hour and 12-hour clock).
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- %f now returns a date with the format '%Y.%m.%d-%H:%M:%S'.
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- %q now returns the quarter of the current year.
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12. The 'typeset' builtin now properly detects and reports options that
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cannot be used together if they are given as part of the same command.
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13. The DEBUG trap has reverted to pre-93t behavior. It is now once again
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reset like other traps upon entering a subshell or ksh-style function,
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as documented, and it is no longer prone to crash or get corrupted.
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14. 'command -x' now always runs an external command, bypassing built-ins.
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____________________________________________________________________________
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KSH-93 VS. KSH-88
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The following is a list of known incompatibilities between ksh-93 and ksh-88.
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I have not included cases that are clearly bugs in ksh-88. I also have
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omitted features that are completely upward compatible.
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1. Functions, defined with name() with ksh-93 are compatible with
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the POSIX standard, not with ksh-88. No local variables are
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permitted, and there is no separate scope. Functions defined
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with the function name syntax, maintain compatibility.
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This also affects function traces.
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2. ! is now a reserved word. As a result, any command by that
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name will no longer work with ksh-93.
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3. The -x attribute of alias and typeset -f is no longer
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effective and the ENV file is only read for interactive
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shells. You need to use FPATH to make function definitions
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visible to scripts.
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4. A built-in command named command has been added which is
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always found before the PATH search. Any script which uses
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this name as the name of a command (or function) will not
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be compatible.
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5. The output format for some built-ins has changed. In particular
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the output format for set, typeset and alias now have single
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quotes around values that have special characters. The output
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for trap without arguments has a format that can be used as input.
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6. With ksh-88, a dollar sign ($') followed by a single quote was
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interpreted literally. Now it is an ANSI-C string. You
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must quote the dollar sign to get the previous behavior.
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Also, a $ in front of a " indicates that the string needs
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to be translated for locales other than C or POSIX. The $
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is ignored in the C and POSIX locale.
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7. With ksh-88, tilde expansion did not take place inside ${...}.
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with ksh-93, ${foo-~} will cause tilde expansion if foo is
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not set. You need to escape the ~ for the previous behavior.
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8. Some changes in the tokenizing rules where made that might
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cause some scripts with previously ambiguous use of quoting
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to produce syntax errors.
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9. Programs that rely on specific exit values for the shell,
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(rather than 0 or non-zero) may not be compatible. The
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exit status for many shell failures has been changed.
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10. Built-ins in ksh-88 were always executed before looking for
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the command in the PATH variable. This is no longer true.
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Thus, with ksh-93, if you have the current directory first
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in your PATH, and you have a program named test in your
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directory, it will be executed when you type test; the
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built-in version will be run at the point /bin is found
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in your PATH.
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11. Some undocumented combinations of argument passing to ksh
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builtins no longer works since ksh-93 is getopts conforming
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with respect to its built-ins. For example, typeset -8i
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previously would work as a synonym for typeset -i8.
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12. Command substitution and arithmetic expansion are now performed
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on PS1, PS3, and ENV when they are expanded. Thus, ` and $(
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as part of the value of these variables must be preceded by a \
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to preserve their previous behavior.
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13. The ERRNO variable has been dropped.
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14. If the file name following a redirection symbol contain pattern
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characters they will only be expanded for interactive shells.
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15. The arguments to a dot script will be restored when it completes.
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16. The list of tracked aliases is not displayed with alias unless
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the -t option is specified.
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17. The POSIX standard requires that test "$arg" have exit status
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of 0, if and only if $arg is null. However, since this breaks
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programs that use test -t, ksh-93 treats an explicit test -t
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as if the user had entered test -t 1.
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18. The ^T directive of emacs mode has been changed to work the
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way it does in gnu-emacs.
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19. ksh-88 allowed unbalanced parentheses within ${name op val} whereas
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ksh-93 does not. Thus, ${foo-(} needs to be written as ${foo-\(}
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which works with both versions.
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20. kill -l in ksh-93 lists only the signal names, not their numerical
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values.
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21. Local variables defined by typeset are statically scoped in
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ksh-93. In ksh-88 they were dynamically scoped although this
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behavior was never documented.
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22. The value of the variable given to getopts is set to ? when
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the end-of-options is reached to conform to the POSIX standard.
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23. Since the POSIX standard requires that octal constants be
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recognized, doing arithmetic on typeset -Z variables can
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yield different results that with ksh-88. Most of these
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differences were eliminated in ksh-93o. Starting in ksh-93u+, the
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let command no longer recognizes octal constants starting with 0
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for compatibility with ksh-88 unless the option letoctal is on.
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24. Starting after ksh-93l, If you run ksh name, where name does
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not contain a /, the current directory will be searched
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before doing a path search on name as required by the POSIX
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shell standard.
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25. In ksh-93, cd - will output the directory that it changes
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to on standard output as required by X/Open. With ksh-88,
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this only happened for interactive shells.
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26. As an undocumented feature of ksh-88, a leading 0 to an
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assignment of an integer variable caused that variable
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to be treated as unsigned. This behavior was removed
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starting in ksh-93p.
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27. The getopts builtin in ksh-93 requires that optstring contain
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a leading + to allow options to begin with a +.
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28. In emacs/gmacs mode, control-v will not display the version when
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the stty lnext character is set to control-v or is unset.
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The sequence escape control-v will display the shell version.
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29. In ksh-88, DEBUG traps were executed. after each command. In ksh-93
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DEBUG traps are executed before each command.
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30. In ksh-88, a redirection to a file name given by an empty string was
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ignored. In ksh-93, this is an error.
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I am interested in expanding this list so please let me know if you
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uncover any others.
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