OpenBSD-4.6/bin/ksh/NOTES
$OpenBSD: NOTES,v 1.11 2007/08/02 11:05:54 fgsch Exp $
General features of at&t ksh88 that are not (yet) in pdksh:
- exported aliases and functions (not in ksh93).
- set -t.
- signals/traps not cleared during functions.
- trap DEBUG, local ERR and EXIT traps in functions.
- ERRNO parameter.
- doesn't have posix file globbing (eg, [[:alpha:]], etc.).
- use of an `agent' to execute unreadable/setuid/setgid shell scripts
(don't ask).
- read/select aren't hooked in to the command line editor
- the last command of a pipeline is not run in the parent shell
Known bugs (see also BUG-REPORTS and PROJECTS files):
Variable parsing, Expansion:
- some specials behave differently when unset (eg, IFS behaves like
" \t\n") others lose their special meaning. IFS/PATH taken care of,
still need to sort out some others (eg, TMOUT).
Parsing,Lexing:
- line numbers in errors are wrong for nested constructs. Need to
keep track of the line a command started on (can use for LINENO
parameter as well).
- a $(..) expression nested inside double quotes inside another $(..)
isn't parsed correctly (eg, $(echo "foo$(echo ")")") )
Commands,Execution:
- setting special parameters that have side effects when
changed/restored (ie, HISTFILE, OPTIND, RANDOM) in front
of a command (eg, HISTFILE=/foo/bar echo hi) effects the parent
shell. Note that setting other (not so special) parameters
does not effect the parent shell.
- `echo hi | exec cat -n' causes at&t to exit, `exec echo hi | cat -n'
does not. pdksh exits for neither. Don't think POSIX requires
an exit, but not sure.
- `echo foo | read bar; echo $bar' prints foo in at&t ksh, nothing
in pdksh (ie, the read is done in a separate process in pdksh).
Misc:
Known problems not caused by ksh:
- after stoping a job, emacs/vi is not re-entered. Hitting return
prints the prompt and everything is fine again. Problem (often
involving a pager like less) is related to order of process
scheduling (shell runs before `stop'ed (sub) processes have had a chance
to clean up the screen/terminal).
Known differences between pdksh & at&t ksh (that may change)
- vi:
- `^U': at&t: kills only what has been inserted, pdksh: kills to
start of line
- at&t ksh login shells say "Warning: you have running jobs" if you
try to exit when there are running jobs. An immediate second attempt
to exit will kill the jobs and exit. pdksh does not print a warning,
nor does it kill running jobs when it exits (it does warn/kill for
stopped jobs).
- TMOUT: at&t prints warning, then waits another 60 seconds. If on screwed
up serial line, the output could cause more input, so pdksh just
prints a message and exits. (Also, in at&t ksh, setting TMOUT has no
effect after the sequence "TMOUT=60; unset TMOUT", which could be
useful - pdksh may do this in the future).
- in pdksh, if the last command of a pipeline is a shell builtin, it is
not executed in the parent shell, so "echo a b | read foo bar" does not
set foo and bar in the parent shell (at&t ksh will).
This may get fixed in the future, but it may take a while.
- in pdksh, set +o lists the options that are currently set, in at&t ksh
it is the same as set -o.
- in pdksh emacs mode, ^T does what gnu emacs does, not what at&t ksh
does.
- in ksh93, `. name' calls a function (defined with function) with POSIX
semantics (instead of ksh semantics). in pdksh, . does not call
functions.
- test: "test -f foo bar blah" is the same as "test -f foo" (the extra
arguments, of which there must be at least 2, are ignored) - pdksh
generates an error message (unexpected operator/operand "bar") as it
should. Sometimes used to test file globs (e.g., if test -f *.o; ...).
- if the command 'sleep 5 && /bin/echo blah' is run interactively and
is the sleep is stopped (^Z), the echo is run immediately in pdksh.
In at&t ksh, the whole thing is stopped.
- LINENO:
- in ksh88 variable is always 1 (can't be changed) in interac mode;
in pdksh it changes.
- Value of LINENO after it has been set by the script in one file
is bizarre when used in another file.
Known differences between pdksh & at&t ksh (that are not likely to change)
- at&t ksh seems to catch or ignore SIGALRM - pdksh dies upon receipt
(unless it's traped of course)
- typeset:
- at&t ksh overloads -u/-l options: for integers, means unsigned/long,
for strings means uppercase/lowercase; pdksh just has the
upper/lower case (which can be useful for integers when base > 10).
unsigned/long really should have their own options.
- at&t ksh can't have justified integer variables
(eg, typeset -iR5 j=10), pdksh can.
- in pdksh, number arguments for -L/-R/-Z/-i must follow the option
character, at&t allows it at the end of the option group (eg,
at&t ksh likes "typeset -iu5 j", pdksh wants "typeset -i5 -u j"
or "typeset -ui5 j"). Also, pdksh allows "typeset -i 5 j" (same
as "typeset -i5 j"), at&t ksh does not allow this.
- typeset -R: pdksh strips trailing space type characters (ie,
uses isspace()), at&t ksh only skips blanks.
- at&t ksh allows attributes of read-only variables to be changed,
pdksh allows only the export attribute to be set.
- (some) at&t ksh allows set -A of readonly variables, pdksh does not.
- at&t ksh allows command assignments of readonly variables (eg, YY=2 cat),
pdksh does not.
- at&t ksh does not exit scripts when an implicit assignment to an integer
variable fails due to an expression error: eg,
echo 2+ > /tmp/x
unset x; typeset -i x
read x < /tmp/x
echo still here
prints an error and then prints "still here", similarly for
unset x; typeset -i x
set +A x 1 2+ 3
echo still here
and
unset x y; typeset -i x y; set +A y 10 20 30
set +A x 1 1+y[2+] 3
echo still here
pdksh exits a script in all the above cases. (note that both shells
exit for:
unset x; typeset -i x
for x in 1 2+ 3; do echo x=$x; done
echo still here
).
- at&t ksh seems to allow function calls inside expressions
(eg, typeset -i x='y(2)') but they do not seem to be regular functions
nor math functions (eg, pow, exp) - anyone known anything about this?
- `set -o nounset; unset foo; echo ${#foo}`: at&t ksh prints 0; pdksh
generates error. Same for ${#foo[*]} and ${#foo[@]}.
- . file: at&t ksh parses the whole file before executing anything,
pdksh executes as it parses. This means aliases defined in the file
will affect how pdksh parses the file, but won't affect how at&t ksh
parses the file. Also means pdksh will not parse statements occurring
after a (executed) return statement.
- a return in $ENV in at&t ksh will cause the shell to exit, while in
pdksh it will stop executing the script (this is consistent with
what a return in .profile does in both shells).
- at&t ksh does file globbing for `echo "${foo:-"*"}"`, pdksh does not
(POSIX would seem to indicate pdksh is right).
- at&t ksh thinks ${a:##foo} is ok, pdksh doesn't.
- at&t does tilde expansion on here-document delimiters, pdksh does
not. eg.
$ cat << ~michael
~michael
$
works for pdksh, not for at&t ksh (POSIX seems to agree with pdksh).
- in at&t ksh, tracked aliases have the export flag implicitly set
and tracked aliases and normal aliases live in the same name space
(eg, "alias" will list both tracked and normal aliases).
in pdksh, -t does not imply -x (since -x doesn't do anything yet), and
tracked/normal aliases live in separate name spaces.
in at&t ksh, alias accepts + options (eg, +x, +t) - pdksh does not.
in pdksh, alias has a -d option to allow examination/changing of
cached ~ entries, also unalias has -d and -t options (unalias -d
is useful if the ~ cache gets out of date - not sure how at&t deals
with this problem (it does cache ~ entries)).
- at&t ksh will stop a recursive function after about 60 calls; pdksh
will not since the limit is arbitrary and can't be controlled
by the user (hit ^C if you get in trouble).
- the wait command (with and without arguments) in at&t ksh will wait for
stopped jobs when job control is enabled. pdksh doesn't.
- at&t ksh automatically sets the bgnice option for interactive shells;
pdksh does not.
- in at&t ksh, "eval `false`; echo $?" prints 1, pdksh prints 0 (which
is what POSIX says it should). Same goes for "wait `false`; echo $?".
(same goes for "set `false`; echo $?" if posix option is set - some
scripts that use the old getopt depend on this, so be careful about
setting the posix option).
- in at&t ksh, print -uX and read -uX are interrperted as -u with no
argument (defaults to 1 and 0 respectively) and -X (which may or
may not be a valid flag). In pdksh, -uX is interpreted as file
descriptor X.
- in at&t ksh, some signals (HUP, INT, QUIT) cause the read to exit, others
(ie, everything else) do not. When it does cause exiting, anything read
to that point is used (usually an empty line) and read returns with 0
status. pdksh currently does similar things, but for TERM as well and
the exit status is 128+<signal-number> - in future, pdksh's read will
do this for all signals that are normally fatal as required by POSIX.
(POSIX does not require the setting of variables to null so applications
shouldn't rely on this).
- in pdksh, ! substitution done before variable substitution; in at&t ksh
it is done after substitution (and therefor may do ! substitutions on
the result of variable substitutions). POSIX doesn't say which is to be
done.
- pwd: in at&t ksh, it ignores arguments; in pdksh, it complains when given
arguments.
- the at&t ksh does not do command substition on PS1, pdksh does.
- ksh93 allows ". foo" to run the function foo if there is no file
called foo (go figure).
- field splitting (IFS): ksh88/ksh93 strip leading non-white space IFS
chars, pdksh (and POSIX, I think) leave them intact. e.g.
$ IFS="$IFS:"; read x; echo "<$x>"
::
prints "<>" in at&t ksh, "<::>" in pdksh.
- command completion: at&t ksh will do completion on a blank line (matching
all commands), pdksh does not (as this isn't very useful - use * if
you really want the list).
- co-processes: if ksh93, the write portion of the co-process output is
closed when the most recently started co-process exits. pdksh closes
it when all the co-processes using it have exited.
- pdksh accepts empty command lists for while and for statements, while
at&t ksh (and sh) don't. Eg., pdksh likes
while false ; do done
but ksh88 doesn't like it.
- pdksh bumps RANDOM in parent after a fork, at&t ksh bumps it in both
parent and child:
RANDOM=1
echo child: `echo $RANDOM`
echo parent: $RANDOM
will produce "child: 16838 parent: 5758" in pdksh, while at&t ksh
will produce "child: 5758 parent: 5758".
Oddities in ksh (pd & at&t):
- array references inside (())/$(()) are strange:
$(( x[2] )) does the expected, $(( $x[2] )) doesn't.
- `typeset -R3 X='x '; echo "($X)"` produces ( x) - trailing
spaces are stripped.
- typeset -R turns off Z flag.
- both shells have the following mis-feature:
$ x='function xx {
cat -n <<- EOF
here we are in xx
EOF
}'
$ (eval "$x"; (sleep 2; xx) & echo bye)
[1] 1234
bye
$ xx: /tmp/sh1234.1: cannot open
- bizarre special handling of alias/export/readonly/typeset arguments
$ touch a=a; typeset a=[ab]; echo "$a"
a=[ab]
$ x=typeset; $x a=[ab]; echo "$a"
a=a
$
- both ignore SIGTSTP,SIGTTIN,SIGTTOU in exec'd processes when talking
and not monitoring (at&t ksh kind of does this). Doesn't really make
sense.
(Note that ksh.att -ic 'set +m; check-sigs' shows TSTP et al aren't
ignored, while ksh.att -ic 'set +m^J check-sigs' does... very strange)
- when tracing (set -x), and a command's stderr is redirected, the trace
output is also redirected. so "set -x; echo foo 2> /tmp/O > /dev/null"
will create /tmp/foo with the lines "+ > /dev/null" and "+ echo foo".
- undocumented at&t ksh feature: FPATH is searched after PATH if no
executable is found, even if typeset -uf wasn't used.
at&t ksh bugs:
[various versions:
MIPS m120 RISC/os 5.0: Version 11/16/88d
Dec alpha osf/1 v1.3: OSF/1 Version 11/16/88d NLS
HP pa HP-UX 9.01: Version 11/16/88
]
- (only hpux)
$ _[2]=hi
Bus error (core dumped)
- (only riscos, hpux)
$ typeset x[
$
- (only osf/1)
$ A=B cat << EOF
.$A.
EOF
Segmentation fault(coredump)
$
- (only osf/1)
$ read "?foo "
foo Foo
$ set | grep Foo
=Foo
$
- (all)
$ typeset -i A
$ typeset -L3 A
$ typeset -l A
Illegal instruction (core dumped)
- (all)
$ for i in a b c ; do echo $i, ${i[2]}, ${i[10]} ; done
a, ,
a, , b
a, , c
$
- (all)
$ echo ${abc:-G { I } K }
G { I K }
$
$ abc=hi
$ echo ${abc:-G { I } K }
hi K }
$
The second echo should only have printed `hi'.
- (all)
$ echo ${abc:- > foo}
syntax error: > unexpected
$
- (all? hpux) read reads too much from pipe (when pipe isn't stdin)
print 'hi\nthere' | ksh 8<&0 0< /dev/tty
$ read -u8 x
$ print $x
hi
$ cat 0<&8
$ read -u8 y
$ print $y
there
$
- (all)
$ umask 0
$ umask
00
$
- (osf, mips, !hpux)
$ exec alias
alias: not found
(shell dead)
- (all) non-white space IFS in non-substitution not preserved
$ IFS="$IFS:"
$ echo : "$@" # this is ok
:
$ echo :"$@" # this should print : too (me thinks)
$
- (only osf/1)
$ set +m
$ sleep 1 & # wait for a sec or two
$ jobs
Memory fault (core dumped)
- (all)
$ (sleep 1 & echo hi) &
[1] 123
$ [1] 234
hi
- (osf/1, mips)
$ getopts abc optc -a -b -c
$ getopts abc optc -a -b -c
$ getopts abc optc -a
Memory fault (core dumped)
- (osf/1) POSIX says OPTIND shall be initialized to 1
$ echo $OPTIND
0
$
- (osf/1 + others?)
$ typeset -ri r=10
$ let r=12
$ echo $r
12
$
- (osf/1 + others?)
$ typeset -i a
$ typeset -L3 a
Memory fault (core dumped)
- (osf/1 + others?): -L strips leading \ \t\n\r, -R only strips trailing
spaces
$ typeset -L3 x
$ x=' ^I^J^M 2'
$ echo "($x)"
(2 )
$ typeset -R3 y
$ x='2^I^J^M '
$ echo "($x)"
(^I^J^M)
$
- (osf/1 + others?)
$ typeset +i RANDOM
Memory fault (core dumped)
- (osf/1 + others?): -L/-R/-Z clear -l/-u after assignment and vise versa
$ typeset -u x=ab
$ echo "($x)"
(AB)
$ typeset -L4 x=def
$ echo "($x)"
(DEF )
$ typeset | grep ' x$'
leftjust 4 x
$
$ typeset -L4 x=def
$ echo "($x)"
(def )
$ typeset -u x=ab
$ echo "($x)"
(AB )
$ typeset | grep ' x$'
uppercase x
$
$ typeset -i x
$ x='2()'
$ x='()'
$ x='2(4)'
- (osf/1, others?)
$ unset foo
$ echo "${foo:-"*"}"
<results of * expansion>
$
- (osf/1, others?)
$ alias blah
blah: alias not found
$ alias -x blah | grep blah
blah
$ type blah
Memory fault (core dumped)
- (osf/1, others?)
$ trap 'echo hi; false' ERR
$ false
hi
hi
....
Memory fault (core dumped)
- (osf/1, others?)
$ typeset +i ERRNO
Memory fault (core dumped)
- (osf/1, others?)
$ X=abcdef
$ echo ${X#a{b,c}e} # does not match {} inside word part of ${..#..}
abcdefe}
$
- (osf/1, others?)
$ x=f=abcdef
$ echo ${f#a|abc}
def
$ echo ${f#abc|a}
bcdef
$ echo ${f#abc|a|d}
abcdef
$
- (osf/1, hp-ux, others?)
$ i() echo hi
$ typeset -f
function i
{
hi
$
- (osf/1, others?)
$ function X {
echo start of X
function Y {
echo in Y
}
echo end of X
}
$ X
start of X
end of X
$ typeset -f
function X
{
echo start of X
function Y {
echo in Y
}
echo end of X
}
function Y
{
echo in Y
echo end of X
}
}
$
- (osf/1, others?)
$ while read x; do print -r "A $x"; done |&
[1] 18212
$ exec 8<&p
$ kill %1
Memory fault
- (osf/1, others?) Error only happens for builtin commands (/bin/echo works)
$ while read x; do print -r "A $x"; done |&
[1] 18212
$ echo hi <&p
hi
$ echo hi <&p
ksh: p: bad file unit number
$ while read x; do print -r "A $x"; done |&
ksh: process already exists
$
- (osf/1, others?) in restricted shells, command -p should not work.
$ PATH=/tmp ksh -r
$ print hi | command -p cat -n
1 hi
$
- (osf/1, others?) error message wrong for autoload files that don't define
functions
$ FPATH=/tmp
$ echo echo hi there > /tmp/aja
$ aja
hi there
ksh: echo: not found
$
- (SunOS M-12/28/93d):
$ cat -n << X $(
> echo foo
> )
> X
> echo bar
)
./ksh93: X: cannot open [No such file or directory]
Memory fault (core dumped)
POSIX sh questions (references are to POSIX 1003.2-1992)
- arithmetic expressions: how are empty expressions treated?
(eg, echo $(( ))). at&t ksh (and now pdksh) echo 0.
Same question goes for `test "" -eq 0' - does this generate an error
or, if not, what is the exit code?
- should tilde expansion occur after :'s in the word part of ${..=..}?
(me thinks it should)
- if a signal is received during the execution of a built-in,
does the builtin command exit or the whole shell?
- is it legal to execute last command of pipeline in current
execution environment (eg, can "echo foo | read bar" set
bar?)
- what action should be taken if there is an error doing a dup due
to system limits (eg, not enough feil destriptors): is this
a "redirection error" (in which case a script will exit iff the
error occured while executing a special built-in)?
IMHO, shell should exit script. Couldn't find a blanket statement
like "if shell encounters an unexpected system error, it shall
exit non-interactive scripts"...
POSIX sh bugs (references are to POSIX 1003.2-1992)
- in vi insert mode, ^W deletes to beginning of line or to the first
blank/punct character (para at line 9124, section 3). This means
"foo ^W" will do nothing. This is inconsistent with the vi
spec, which says delete preceding word including and interceding
blanks (para at line 5189, section 5).
- parameter expansion, section 3.6.2, line 391: `in each case that a
value of word is needed (..), word shall be subjected to tilde
expansion, parameter expansion, ...'. Various expansions should not
be performed if parameter is in double quotes.
- the getopts description says assigning OPTIND a value other than 1
produces undefined results, while the rationale for getopts suggests
saving/restoring the OPTIND value inside functions (since POSIX
functions don't do the save/restore automatically). Restoring
OPTIND is kind of dumb since getopts may have been in the middle
of parsing a group of flags (eg, -abc).
- unclear whether arithmetic expressions (eg, $((..))) should
understand C integer constants (ie, 0x123, 0177). at&t ksh doesn't
and neither does pdksh.
- `...` definition (3.6.3) says nothing about backslash followed by
a newline, which sh and at&t ksh strip out completely. e.g.,
$ show-args `echo 'X
Y'`
Number of args: 1
1: <XY>
$
POSIX would indicate the backslash-newline would be preserved.
- does not say how "cat << ''" is to be treated (illegal, read 'til
blank line, or read 'til eof). at&t ksh reads til eof, bourne shell
reads 'til blank line. pdksh reads 'til blank line.