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2 KSH-93 VS. KSH-88
5 The following is a list of known incompatibilities between ksh-93 and ksh-88.
6 I have not include cases that are clearly bugs in ksh-88. I also have
7 omitted features that are completely upward compatible.
9 1. Functions, defined with name() with ksh-93 are compatible with
10 the POSIX standard, not with ksh-88. No local variables are
11 permitted, and there is no separate scope. Functions defined
12 with the function name syntax, maintain compatibility.
13 This also affects function traces.
15 2. ! is now a reserved word. As a result, any command by that
16 name will no longer work with ksh-93.
18 3. The -x attribute of alias and typeset -f is no longer
19 effective and the ENV file is only read for interactive
20 shells. You need to use FPATH to make function definitions
21 visible to scripts.
23 4. A built-in command named command has been added which is
24 always found before the PATH search. Any script which uses
25 this name as the name of a command (or function) will not
26 be compatible.
28 5. The output format for some built-ins has changed. In particular
29 the output format for set, typeset and alias now have single
30 quotes around values that have special characters. The output
31 for trap without arguments has a format that can be used as input.
33 6. With ksh-88, a dollar sign ($') followed by a single quote was
34 interpreted literally. Now it is an ANSI-C string. You
35 must quote the dollar sign to get the previous behavior.
36 Also, a $ in front of a " indicates that the string needs
37 to be translated for locales other than C or POSIX. The $
38 is ignored in the C and POSIX locale.
40 7. With ksh-88, tilde expansion did not take place inside ${...}.
41 with ksh-93, ${foo-~} will cause tilde expansion if foo is
42 not set. You need to escape the ~ for the previous behavior.
44 8. Some changes in the tokenizing rules where made that might
45 cause some scripts with previously ambiguous use of quoting
46 to produce syntax errors.
48 9. Programs that rely on specific exit values for the shell,
49 (rather than 0 or non-zero) may not be compatible. The
50 exit status for many shell failures has been changed.
52 10. Built-ins in ksh-88 were always executed before looking for
53 the command in the PATH variable. This is no longer true.
54 Thus, with ksh-93, if you have the current directory first
55 in your PATH, and you have a program named test in your
56 directory, it will be executed when you type test; the
57 built-in version will be run at the point /bin is found
58 in your PATH.
60 11. Some undocumented combinations of argument passing to ksh
61 builtins no longer works since ksh-93 is getopts conforming
62 with respect to its built-ins. For example, typeset -8i
63 previously would work as a synonym for typeset -i8.
65 12. Command substitution and arithmetic expansion are now performed
66 on PS1, PS3, and ENV when they are expanded. Thus, ` and $(
67 as part of the value of these variables must be preceded by a \
68 to preserve their previous behavior.
70 13. The ERRNO variable has been dropped.
72 14. If the file name following a redirection symbol contain pattern
73 characters they will only be expanded for interactive shells.
75 15. The arguments to a dot script will be restored when it completes.
77 16. The list of tracked aliases is not displayed with alias unless
78 the -t option is specified.
80 17. The POSIX standard requires that test "$arg" have exit status
81 of 0, if and only if $arg is null. However, since this breaks
82 programs that use test -t, ksh93 treats an explicit test -t
83 as if the user had entered test -t 1.
85 18. The ^T directive of emacs mode has been changed to work the
86 way it does in gnu-emacs.
88 19. ksh-88 allowed unbalanced parenthes within ${name op val} whereas
89 ksh-93 does not. Thus, ${foo-(} needs to be written as ${foo-\(}
90 which works with both versions.
92 20. kill -l in ksh-93 lists only the signal names, not their numerical
93 values.
95 21. Local variables defined by typeset are statically scoped in
96 ksh93. In ksh88 they were dynamically scoped although this
97 behavior was never documented.
99 22. The value of the variable given to getopts is set to ? when
100 the end-of-options is reached to conform to the POSIX standard.
102 23. Since the POSIX standard requires that octal constants be
103 recongnized, doing arithmetic on typeset -Z variables can
104 yield different results that with ksh88. Most of these
105 differences were eliminated in ksh93o.
107 24. Starting after ksh93l, If you run ksh name, where name does
108 not contain a /, the current directory will be searched
109 before doing a path search on name as required by the POSIX
110 shell standard.
112 25. In ksh93, cd - will output the directory that it changes
113 to on standard output as required by X/Open. With ksh88,
114 this only happened for interactive shells.
116 26. As an undocumented feature of ksh-88, a leading 0 to an
117 assignment of an integer variable caused that variable
118 to be treated as unsigned. This behavior was removed
119 starting in ksh93p.
121 27. The getopts builtin in ksh93 requires that optstring contain
122 a leading + to allow options to begin with a +.
124 28. In emacs/gmacs mode, control-v will not display the version when
125 the stty lnext character is set to control-v or is unset.
126 The sequence escape control-v will display the shell version.
128 29. In ksh88, DEBUG traps were executed. after each command. In ksh93
129 DEBUG traps are exeucted before each command.
131 30. In ksh88, a redirection to a file name given by an empty string was
132 ignored. In ksh93, this is an error.
133 I am interested in expanding this list so please let me know if you
134 uncover any others.