Hello,
Clearing out the remainder of my "maybe bugs" file, in no particular order.
1. Arithmetic assignment precedence / associativity.
Most shells (and GCC) consider not grouping the assignment in a situation like
this an error. Bash tolerates it, apparently reversing associativity:
: $((1 == x = 1)) # Error in dash/ksh/mksh/zsh/etc
#include <stdio.h>
int main() {
int n;
5 == n = 5 && printf("%d\n", n); // Error
return 0;
}
2. += environment assignments
2a. POSIX mode += w/ special builtin.
#!/usr/bin/env bash
for sh in bash ~/doc/programs/bash43 ksh mksh zsh; do
printf '%-7s %s\n' "${sh##*/}:" "$("$sh" /dev/fd/0)"
done <<\EOF
${ZSH_VERSION+false}${BASH_VERSION+${POSIXLY_CORRECT=}}||emulate ksh
x=2; x+=5 eval printf '"$x "'; echo "$x" # TESTCASE
EOF
shell | inner | outer
bash: 5 2 #(4.2.45)
bash43: 5 5
ksh: 25 25
mksh: 25 25
zsh: 25 25
2b. Integer attribute with += environment assignment.
The manual doesn't document an exception for += when a command is present. Some
shells do arithmetic for += with a command (bash doesn't).
#!/usr/bin/env bash
for sh in bash ~/doc/programs/bash43 ksh mksh zsh; do
printf '%-7s %s\n' "${sh##*/}:" "$("$sh" /dev/fd/0)"
done <<\EOF
${ZSH_VERSION+false}${BASH_VERSION+${POSIXLY_CORRECT=}}||emulate ksh
typeset -i x=2
x+=5 eval printf '"$x "'; echo "$x" # TESTCASE
EOF
bash: 5 2
bash43: 5 5
ksh: 7 7
mksh: 25 25
zsh: 7 7
3. RETURN trap doesn't fire upon leaving a function via break or continue.
This is a very minor possibly intentional detail. The way break works in this
situation is interesting -- maybe useful.
function f {
case $1 in
3) while :; do f $(($1 - 1)) done
;;
0)
trap "printf \$1" RETURN
break
;;
*) f $(($1 - 1))
esac
}
# Prints "345" instead of "12345"
f 5
4. Invalid compound assignments can become string assignments.
If the first character of a regular assignment is an unquoted "(", then if
there's a a matching ")", the remainder of the assignment up to the next
unquoted metacharacter is assigned as a string. Zsh and ksh honor the ")" of
a compound assignment as a metacharacter (to separate commands). mksh and dash
treat such an assignment as an error.
$ x=()abc; typeset -p x # It might be better to require quoting here.
declare -- x="()abc"
$ ksh -xc 'x=(foo)typeset -p x'
+ x=( foo )
+ typeset -p x
typeset -a x=(foo)
5. Easter egg (test + redirect + $[])
$ trap 'echo "$BASH_COMMAND"; trap - DEBUG' DEBUG
$ [ <& $[ ] [ = [ && printf '%s\n' "$_ ...ha :)"
[ [ = [ 0<&$[ ]
[ ...ha :)
I like this. :)
6. Indirection combined with another modifier expands arrays to a single word.
$ a=({a..c}) b=a[@]; printf '<%s> ' "${!b}"; echo; printf '<%s> '
"${!b/%/foo}"; echo
<a> <b> <c>
<a b cfoo>
I might have already reported this but can't find it. Ignore if so.
--
Dan Douglas
