path: root/tests/sh.test

#!/bin/echo no

[ -f testing.sh ] && . testing.sh

# TODO make fake pty wrapper for test infrastructure

# testing "name" "command" "result" "infile" "stdin"
# texpect "name" "command" [R]I/O/E"string" X[ERR]

# Use "bash" name for host, "sh" for toybox. (/bin/sh is often defective.)
[ -z "$SH" ] && { [ -z "$TEST_HOST" ] && SH="sh" || export SH="bash" ; }
# The expected prompt is different for root vs normal user
[ $UID -eq 0 ] && P='# ' || P='$ '
# insulate shell child process to get predictable results
SS="env -i PATH=${PATH@Q} PS1='\\$ ' $SH --noediting --noprofile --norc -is"

# Wrap txpect for shell testing
shxpect() {
  X="$1"
  shift
  txpect "$X" "$SS" E"$P" "$@" X0
}

shxpect "prompt and exit" I$'exit\n'
shxpect "prompt and echo" I$'echo hello\n' O$'hello\n' E"$P"
shxpect "redir" I$'cat<<<hello\n' O$'hello\n' E"$P"
shxpect "redirect err" I$'echo > /dev/full\n' E E"$P" X1
shxpect "wait for <(exit)" I$'cat <(echo hello 1>&2)\n' E$'hello\n' E"$P"

# Test shell command line (-c and how scripts run) before changing EVAL
testing '-c "" exit status 0' '$SH -c "" && echo $?' '0\n' '' ''
testing '-c args' "\$SH -c 'echo \$0,\$1,\$2,\$3' one two three four five" \
  "one,two,three,four\n" "" ""
testing '-c args2' "\$SH -c 'echo \${10}' a b c d e f g h i j k l" "k\n" "" ""
testing '-c arg split' \
  "$SH -c 'for i in a\"\$@\"b;do echo =\$i=;done;echo \$0' 123 456 789" \
  "=a456=\n=789b=\n123\n" "" ""
testing '-c arg split2' \
  "$SH -c 'for i in a\"\$* \$@\"b; do echo =\$i=;done' one two three four five"\
  "=atwo three four five two=\n=three=\n=four=\n=fiveb=\n" "" ""
testing '-c arg count' "$SH -c 'echo \$#' 9 8 7 6 1 2 3 4" "7\n" "" ""
testing 'trailing \' "$SH -c 'echo \'" '\\\n' '' ''
testing "trailing \\ in ''" "$SH -c \$'echo \\'one\\\\\\ntwo\\''" \
  'one\\\ntwo\n' '' ''
testing 'trailing \ in ""' "$SH -c \$'echo \"one\\\\\\ntwo\"'" 'onetwo\n' \
  '' ''
testing 'vanishing \' "$SH -c \$'echo \\\\\\n a'" 'a\n' '' ''
testing 'command\ arg' "$SH -c \$'echo\\\\\\n  abc'" 'abc\n' '' ''
testing "exec3" '$C -c "{ exec readlink /proc/self/fd/0;} < /proc/self/exe"' \
  "$(readlink -f $C)\n" "" ""
testing 'arg shift' "$SH -c '"'for i in "" 2 1 1 1; do echo $? $1; shift $i; done'"' one two three four five" \
  "0 two\n0 three\n0 five\n0\n1\n" "" ""
testing '(subshell)' '$SH -c "(echo hello)"' 'hello\n' '' ''
testing 'syntax' '$SH -c "if true; then echo hello | fi" 2>/dev/null || echo x'\
  'x\n' '' ''
testing 'syntax2' '$SH -c "for;i 0" 2>&1 | { grep -qi syntax && echo yes; }' \
  'yes\n' '' ''

# The bash man page is lying when it says $_ starts with an absolute path.
ln -s "$(which $SH)" bash
testing 'non-absolute $_' "./bash -c 'echo \$_'" './bash\n' '' ''
rm bash

testing 'exec exitval' "$SH -c 'exec echo hello' && echo \$?" "hello\n0\n" "" ""
testing 'simple script' '$SH input' 'input\n' 'echo $0' ''
testing 'simple script2' '$SH ./input two;echo $?' './input+two\n42\n' \
  '\necho $0+$1\n\nexit 42' ''
# this segfaults bash
toyonly testing 'recursion guard' \
  '$SH input 2>/dev/null; [ $? -lt 128 ] && echo pass' 'pass\n' \
  'source input' ''
testing '$LINENO 1' "$SH input" "1\n" 'echo $LINENO' ''

mkdir sub
echo echo hello > sub/script
testing 'simple script in $PATH' "PATH='$PWD/sub:$PATH' $SH script" \
  'hello\n' '' ''
rm -rf sub

testing "script file" "chmod +x input; ./input" "hello\n" "#!$C\necho hello" ""
testing 'IFS $*' "$SH -c 'IFS=xy; echo \"\$*\"' one two tyree" "twoxtyree\n" \
  "" ""
# Without the \n\n bash 5 emits SHLVL=0
testing 'default exports' \
  "env -i \"$(which $SH)\" --noprofile --norc -c \$'env\n\n' | sort" \
  "PWD=$(pwd)\nSHLVL=1\n_=$(which env)\n" "" ""
# toysh order of operations not matching bash
#testing "leading assignment fail" \
#  "{ \$SH -c 'X=\${a?blah} > walroid';ls walroid;} 2>/dev/null" '' '' ''
testing "lineno" "$SH input" "5 one\n6 one\n5 two\n6 two\n" \
  '#!/bin/bash\n\nfor i in one two\ndo\n  echo $LINENO $i\n  echo $LINENO $i\ndone\n' ""
testing "eval0" "$SH -c 'eval echo \$*' one two three" "two three\n" "" ""

#########################################################################
# Change EVAL to call sh -c for us, using "bash" explicitly for the host.
export EVAL="timeout 10 $SH -c"

# From here on, tests run within the new shell by default.

testing 'return code' 'if false; then echo true; fi; echo $?' '0\n' '' ''
testing 'return code 2' 'if true; then false; fi; echo $?' '1\n' '' ''
testing 'return code 3' 'x=0; while [ $((x++)) -lt 2 ]; do echo $x; done; echo $?' '1\n2\n0\n' '' ''
testing 'local var +whiteout' \
  'l=X;x(){ local l=47; echo $l;unset l; echo l=$l;};x;echo $l' '47\nl=\nX\n' \
  '' ''
testing 'escape passthrough' 'echo -e "a\nb\nc\td"' 'a\nb\nc\td\n' '' ''

testing 'trailing $ is literal' 'echo $' '$\n' '' ''
testing 'work after HERE' $'cat<<0;echo hello\npotato\n0' 'potato\nhello\n' '' ''
testing '<<""' $'cat<<"";echo hello\npotato\n\necho huh' 'potato\nhello\nhuh\n'\
  '' ''
testing '<< trailing \' $'cat<<EOF 2>/dev/null\nabcde\nnext\\\nEOF\nEOF' \
  'abcde\nnextEOF\n' '' ''
testing '<< trailing \ 2' $'cat<<EOF\nabcde\nEO\\\nF\necho hello' \
  'abcde\nhello\n' '' ''
ln -s "$(which echo)" echo2
testing "undelimited redirect doesn't eat prefix" './echo2</dev/null hello' \
  'hello\n' '' ''
rm -f echo2
testing 'prefix assignment is local' '{ echo $ABC; } {ABC}</dev/null; echo $3'\
  '10\n\n' '' ''
testing 'quoted line escapes' $'echo "\\\none" \'\\\ntwo\'' 'one \\\ntwo\n' '' ''
testing 'escape makes argument' 'echo \  | wc -c' '2\n' '' ''

# TODO testing 'empty +() is literal' 'echo +()' '+()\n' '' ''

# shxpect "EOF" I$'<<EOF;echo hello'
shxpect 'queued work after HERE' I$'<<0;echo hello\n' E"> " I$'0\n' O$'hello\n'
shxpect '$_ preserved on assignment error' I$'true hello; a=1 b=2 c=${}\n' \
  E E"$P" I$'echo $_\n' O$'hello\n'
shxpect '$_ preserved on prefix error' I$'true hello; a=1 b=2 c=${} true\n' \
  E E"$P" I$'echo $_\n' O$'hello\n'
shxpect '$_ preserved on exec error' I$'true hello; ${}\n' \
  E E"$P" I$'echo $_\n' O$'hello\n'
shxpect '$_ abspath on exec' I$'env | grep ^_=\n' O$'_=/usr/bin/env\n'
testing '$_ literal after exec' 'env >/dev/null; echo $_' 'env\n' '' ''
shxpect '$_ no path for builtin' I$'true; echo $_\n' O$'true\n'
testing 'prefix is local for builtins' 'abc=123; abc=def unset abc; echo $abc' \
  '123\n' '' ''
testing 'prefix localizes magic vars' \
  'SECONDS=123; SECONDS=345 true; echo $SECONDS' '123\n' '' ''
shxpect 'body evaluated before variable exports' I$'a=x${} y${}\n' RE'y${}' X1
testing '$NOTHING clears $_' 'true; $NOTHING; echo $_' '\n' '' ''
testing 'assignment with redirect is persistent, not prefix' \
  'ABC=DEF > potato && rm potato && echo $ABC' 'DEF\n' '' ''
testing '$_ with functions' 'true; x(){ echo $_;}; x abc; echo $_' \
  'true\nabc\n' '' ''

mkdir -p one/two/three
testing 'cd in renamed dir' \
  'cd one/two/three && mv ../../../{one,four} && cd .. && echo ${PWD: -9:9}' \
  '/four/two\n' '' ''
rm -rf one

testing "smoketest" "echo hello" "hello\n" "" ""
testing "assignment" 'x=y; echo $x' 'y\n' '' ''
testing "+= assignment" 'x+=abc; y=def; y+=$x; echo $y' 'defabc\n' '' ''
testing "eval" "eval echo hello" "hello\n" "" ""
testing "eval2" "eval 'echo hello'; echo $?" "hello\n0\n" "" ""
testing "eval3" 'X="echo hello"; eval "$X"' "hello\n" "" ""
testing "eval4" 'eval printf '=%s=' \" hello \"' "= hello =" "" ""
NOSPACE=1 testing "eval5" 'eval echo \" hello \" | wc' ' 1 1 8' "" ""
testing "exec" "exec echo hello" "hello\n" "" ""
testing "exec2" "exec echo hello; echo $?" "hello\n" "" "" 

# ; | && ||
testing "semicolon" "echo one;echo two" "one\ntwo\n" "" ""
testing "simple pipe" "echo hello | cat" "hello\n" "" ""
testing "&&" "true && echo hello" "hello\n" "" ""
testing "&&2" "false && echo hello" "" "" ""
testing "||" "true || echo hello" "" "" ""
testing "||2" "false || echo hello" "hello\n" "" ""
testing "&& ||" "true && false && potato || echo hello" "hello\n" "" ""
testing "&& after function" "x(){ false;};x && echo yes" "" "" ""
testing "|| after function" "x(){ false;};x || echo yes" "yes\n" "" ""

# redirection

testing "redir1" "cat < input" "hello\n" "hello\n" ""
testing "redir2" "echo blah >out; cat out" "blah\n" "" ""
testing "redir3" "echo more >>out; cat out" "blah\nmore\n" "" ""
testing "redir4" "touch /not/exist 2>out||grep -o /not/exist out" \
  "/not/exist\n" "" ""
testing "redir5" "ls out /not/exist &> out2 || wc -l < out2" "2\n" "" ""
testing "redir6" "ls out /not/exist &>>-abc || wc -l < ./-abc" "2\n" "" ""
testing "redir7" "ls out /not/exist |& wc -l" "2\n" "" ""
testing "redir8" 'echo -n $(<input)' "boing" "boing\n" ""
shxpect "redir9" I$'echo hello > out 2>/does/not/exist\n' E E"$P" \
  I$'wc -l < out\n' O$'0\n'
testing "redir10" 'echo hello 3<&3' "hello\n" "" ""
testing "redir11" 'if :;then echo one;fi {abc}<input; cat <&$abc' \
  "one\npotato\n" "potato\n" ""
rm -f out out2 ./-abc

# expansion

testing "tilde expansion" "echo ~" "$HOME\n" "" ""
testing "tilde2" "echo ~/dir" "$HOME/dir\n" "" ""
testing "bracket expansion" \
  "echo {A{a,b}B{c,d}C}" "{AaBcC} {AaBdC} {AbBcC} {AbBdC}\n" "" ""
testing "brackets2" "echo {A{a,b}B{c,d}C,D}" "AaBcC AaBdC AbBcC AbBdC D\n" "" ""
testing "brackets3" 'echo {A"b,c"D}' "{Ab,cD}\n" "" ""
testing "brackets4" 'echo {A"bc",D}' "Abc D\n" "" ""
testing "brackets5" 'echo {A,B,C' "{A,B,C\n" "" ""
testing "brackets6" 'echo {{{{A,B},C}D},E}' "{AD} {BD} {CD} E\n" "" ""
testing "brackets7" 'echo {{{a,b},c,{d,e}},f}' "a b c d e f\n" "" ""
testing "brackets8" 'echo A{a{b,c{B,C}D}d{e,f},g{h,i}j}E' \
  "AabdeE AabdfE AacBDdeE AacBDdfE AacCDdeE AacCDdfE AghjE AgijE\n" "" ""
testing "brackets9" 'echo A{B{C,D}E{N,O},F{G,H}I}J{K,L}M' \
  "ABCENJKM ABCENJLM ABCEOJKM ABCEOJLM ABDENJKM ABDENJLM ABDEOJKM ABDEOJLM AFGIJKM AFGIJLM AFHIJKM AFHIJLM\n" "" ""
for i in /root /var/root /; do [ -e $i ] && EXPECT=$i && break; done
testing "bracket+tilde" "echo {~,~root}/pwd" "$HOME/pwd $EXPECT/pwd\n" "" ""

# Slices

testing '${x#prefix}' 'x=abcde; echo ${x#abc}' 'de\n' '' ''
testing '${x#short} ${x##long}' 'x=banana; echo ${x#b*n} ${x##b*n}' \
  'ana a\n' '' ''
toyonly testing '${x#utf8}' 'x=aそcde; echo ${x##a?c}' 'de\n' '' ''
testing '${x%y}' 'x=potato; echo ${x%t*o} ${x%%t*o}' 'pota po\n' '' ''
testing 'x=${x%y}' 'x=potato; x=${x%t*o}; echo $x' 'pota\n' '' ''
testing 'x=${x//y}' 'x=potato; x=${x//ta}; echo $x' 'poto\n' '' ''
testing '${x^y}' 'x=aaaaa; echo ${x^a}' 'Aaaaa\n' '' ''
testing '${x^^y}' 'x=abccdec; echo ${x^^c}; x=abcdec; echo ${x^^c}' \
  'abCCdeC\nabCdeC\n' '' ''
testing '${x,y}' 'x=BBB; echo ${x,B}' 'bBB\n' '' ''
testing '${x,,y}' 'x=POTATO; echo ${x,,} ${x,,?} ${x,,*} ${x,,T}' \
  'potato potato potato POtAtO\n' '' ''

mkdir -p abc/def/ghi
touch www
testing 'wildcards' 'echo w[v-x]w w[x-v]w abc/*/ghi' \
  'www w[x-v]w abc/def/ghi\n' '' ''
testing 'hidden wildcards' \
  'touch .abc abc && echo *bc && echo and && echo .*bc' \
  'abc\nand\n.abc\n' '' ''

testing "backtick1" 'x=fred; echo `echo $x`' 'fred\n' "" ""
testing "backtick2" 'x=fred; echo `x=y; echo $x`; echo $x' 'y\nfred\n' "" ""
testing '$(( ) )' 'echo ab$((echo hello) | tr e x)cd' "abhxllocd\n" "" ""
testing '$((x=y)) lifetime' 'a=boing; echo $a $a$((a=4))$a $a' 'boing boing44 4\n' '' ''

testing 'quote' "echo \"'\"" "'\n" "" ""

testing "math" 'echo $((1+2))' '3\n' '' ''
testing "[oldmath]" 'echo $[1+2]' '3\n' '' ''
testing "math basic priority" 'echo $((1+2*3**4))' '163\n' '' ''
testing "math paren" 'echo $(((1+2)*3))' '9\n' '' ''
testing "math spaces" 'echo $(( ( 1 + 2 ) * 7 - 5 ** 2 ))' '-4\n' '' ''
testing "((<)) isn't redirect" '((1<2)) </dev/null && echo yes' 'yes\n' '' ''
testing "((>)) isn't redirect" '((1>2)) </dev/null || echo yes' 'yes\n' '' ''
testing "((not math) )" '((echo hello) )' 'hello\n' '' ''
testing "preincrement" 'echo $((++x)); echo $x' '1\n1\n' '' ''
testing "preincrement vs prefix plus" 'echo $((+++x)); echo $x' '1\n1\n' '' ''
testing "predecrement" 'echo $((--x)); echo $x' '-1\n-1\n' '' ''
testing "predecrement vs prefix minus" 'echo $((---x)); echo $x' '1\n-1\n' '' ''
testing "minus-minus-minus" 'echo $((x---7)); echo $x' '-7\n-1\n' '' ''
testing "x---y is x-- -y not x- --y" 'x=1 y=1; echo $((x---y)) $x $y' '0 0 1\n'\
  '' ''
testing "nesting ? :" \
  'for((i=0;i<8;i++)); do echo $((i&1?i&2?1:i&4?2:3:4));done' \
  '4\n3\n4\n1\n4\n2\n4\n1\n' '' ''
testing "inherited assignment suppression" 'echo $((0 ? (x++) : 2)); echo $x' \
  "2\n\n" "" ""
testing "boolean vs logical" 'echo $((2|4&&8))' '1\n' '' ''
testing "&& vs || priority" \
  'echo $((w++||x++&&y++||z++)) w=$w x=$x y=$y z=$z' \
  '0 w=1 x=1 y= z=1\n' '' ''
testing "|| vs && priority" \
  'echo $((w++&&x++||y++&&z++)) w=$w x=$x y=$y z=$z' \
  '0 w=1 x= y=1 z=\n' '' ''
shxpect '/0' I$'echo $((1/0)); echo here\n' E E"$P" I$'echo $?\n' O$'1\n'
shxpect '%0' I$'echo $((1%0)); echo here\n' E E"$P" I$'echo $?\n' O$'1\n'
shxpect '/=0' I$'echo $((x/=0)); echo here\n' E E"$P" I$'echo $?\n' O$'1\n'
shxpect '%=0' I$'echo $((x%=0)); echo here\n' E E"$P" I$'echo $?\n' O$'1\n'

# Loops and flow control
testing "case" 'for i in A C J B; do case "$i" in A) echo got A ;; B) echo and B ;; C) echo then C ;; *) echo default ;; esac; done' \
  "got A\nthen C\ndefault\nand B\n" "" ""
testing 'case;;&' 'case wow in w?w) echo ok;;& wow) echo no; esac' 'ok\nno\n' \
  "" ""
testing "case newlines" \
  $'case i\n\nin\n\na) echo one\n\n;;\n\ni)\n\necho two\n\n;;\n\nesac' \
  "two\n" "" ""
testing "case block" \
  $'case X in\n  X) printf %s "X" || { echo potato;} ;;\nesac' 'X' '' ''
testing 'loop in && ||' \
  'false && for i in a b c; do echo $i; done || echo no' 'no\n' '' ''
testing "continue" 'for i in a b c; do for j in d e f; do echo $i $j; continue 2; done; done' \
  "a d\nb d\nc d\n" "" ""
testing "piped loops that don't exit" \
  'while X=$(($X+1)); do echo $X; done | while read i; do echo $i; done | head -n 5' \
  '1\n2\n3\n4\n5\n' '' ''

# <glinda>A variable occurred</glinda>

testing "expand" 'echo $PWD' "$(pwd)\n" "" ""
testing "expand2" 'echo "$PWD"' "$(pwd)\n" "" ""
testing "expand3" 'echo "$"PWD' '$PWD\n' "" ""
testing "expand4" 'P=x; echo "$P"WD' 'xWD\n' "" ""
testing "dequote" "echo one 'two' ''three 'fo'ur '\\'" \
  'one two three four \\\n' '' ''

testing "leading variable assignment" 'abc=def env | grep ^abc=; echo $abc' \
  "abc=def\n\n" "" ""
testing "leading variable assignments" \
  "abc=def ghi=jkl env | egrep '^(abc|ghi)=' | sort; echo \$abc \$ghi" \
  "abc=def\nghi=jkl\n\n" "" ""
testing "leading assignment occurs after parsing" \
  'abc=def; abc=ghi echo $abc' "def\n" "" ""
testing "leading assignment space" 'X="abc  def"; Y=$X; echo "$Y"' \
  "abc  def\n" "" ""
testing "leading assignment space2" \
  'chicken() { X="$@"; }; chicken a b c d e; echo "$X"' 'a b c d e\n' '' ''
testing "leading assignment fail2" \
  "{ 1blah=123 echo hello;} 2>/dev/null || echo no" "no\n" "" ""
testing "leading assignment redirect" \
  "blah=123 echo hello > walrus && ls walrus" "walrus\n" "" ""
rm -f walrus

testing "{1..5}" "echo {1..5}" "1 2 3 4 5\n" "" ""
testing "{5..1}" "echo {5..1}" "5 4 3 2 1\n" "" ""
testing "{5..1..2}" "echo {5..1..2}" "5 3 1\n" "" ""
testing "{a..z..-3}" "echo {a..z..-3}" "a d g j m p s v y\n" "" ""

mkfifo POIT
testing 'background curly block' \
  '{ sed s/ll/xx/ POIT; }& echo hello > POIT; wait && echo yes' \
  'hexxo\nyes\n' '' ''
rm -f POIT

testing 'background pipe block' \
  'if true; then { sleep .25;bzcat "$FILES"/blkid/ntfs.bz2; }& fi | wc -c' \
  '8388608\n' '' ''
testing 'background variable assignment' 'X=x; X=y & echo $X' 'x\n' '' ''

#$ IFS=x X=xyxz; for i in abc${X}def; do echo =$i=; done
#=abc=
#=y=
#=zdef=

testing "IFS whitespace before/after" \
  'IFS=" x"; A=" x " B=" x" C="x " D=x E="   "; for i in $A $B $C $D L$A L$B L$C L$D $A= $B= $C= $D= L$A= L$B= L$C= L$D=; do echo -n {$i}; done' \
  "{}{}{}{}{L}{L}{L}{L}{}{=}{}{=}{}{=}{}{=}{L}{=}{L}{=}{L}{=}{L}{=}" "" ""
testing "quotes and whitespace" \
  'A="   abc   def   "; for i in ""$A""; do echo =$i=; done' \
  "==\n=abc=\n=def=\n==\n" "" ""
testing "quotes and whitespace2" \
  'A="   abc   def   "; for i in """"$A""; do echo =$i=; done' \
  "==\n=abc=\n=def=\n==\n" "" ""
testing "quotes and whitespace3" \
  'A="   abc   def   "; for i in ""x""$A""; do echo =$i=; done' \
  "=x=\n=abc=\n=def=\n==\n" "" ""

testing "IFS" 'IFS=x; A=abx; echo -n "$A"' "abx" "" ""
testing "IFS2" 'IFS=x; A=abx; echo -n $A' "ab" "" ""
testing "IFS3" 'IFS=x; echo "$(echo abx)"' "abx\n" "" ""
testing "IFS4" 'IFS=x; echo $(echo abx)y' "ab y\n" "" ""
testing "IFS5" 'IFS=xy; for i in abcxdefyghi; do echo =$i=; done' \
  "=abc def ghi=\n" "" ""
testing "curly bracket whitespace" 'for i in {$,} ""{$,}; do echo ="$i"=; done'\
  '=$=\n=$=\n==\n' '' ''

testing 'empty $! is blank' 'echo $!' "\n" "" ""
testing '$! = jobs -p' 'true & [ $(jobs -p) = $! ] && echo yes' "yes\n" "" ""

testing '$*' 'cc(){ for i in $*;do echo =$i=;done;};cc "" "" "" "" ""' \
  "" "" ""
testing '$*2' 'cc(){ for i in "$*";do echo =$i=;done;};cc ""' \
  "==\n" "" ""
testing '$*3... Flame. Flames. Flames, on the side of my face...' \
  'cc(){ for i in "$*";do echo =$i=;done;};cc "" ""' "= =\n" "" ""
testing 'why... oh.' \
  'cc() { echo ="$*"=; for i in =$*=; do echo -$i-; done;}; cc "" ""; echo and; cc ""' \
  '= =\n-=-\n-=-\nand\n==\n-==-\n' "" ""
testing 'really?' 'cc() { for i in $*; do echo -$i-; done;}; cc "" "" ""' \
  "" "" ""
testing 'Sigh.' 'cc() { echo =$1$2=;}; cc "" ""' "==\n" "" ""
testing '$*4' 'cc(){ for i in "$*";do echo =$i=;done;};cc "" "" "" "" ""' \
  "= =\n" "" ""
testing '$*5' 'cc(){ for i in "$*";do echo =$i=;done;};cc "" "abc" ""' \
  "= abc =\n" "" ""

# creating empty arguments without quotes
testing '$* + IFS' \
  'IFS=x; cc(){ for i in $*; do echo =$i=;done;};cc xabcxx' \
  "==\n=abc=\n==\n" "" ""
testing '$@' 'cc(){ for i in "$@";do echo =$i=;done;};cc "" "" "" "" ""' \
  "==\n==\n==\n==\n==\n" "" ""
testing "IFS10" 'IFS=bcd; A=abcde; for i in $A; do echo =$i=; done' \
  "=a=\n==\n==\n=e=\n" "" ""
testing "IFS11" \
  'IFS=x; chicken() { for i in $@$@; do echo =$i=; done;}; chicken one "" abc dxf ghi' \
  "=one=\n==\n=abc=\n=d=\n=f=\n=ghione=\n==\n=abc=\n=d=\n=f=\n=ghi=\n" "" ""
testing "IFS12" 'IFS=3;chicken(){ return 3;}; chicken;echo 3$?3' '3 3\n' "" ""

testing "IFS combinations" \
  'IFS=" x"; A=" x " B=" x" C="x " D=x E="   "; for i in $A $B $C $D L$A L$B L$C L$D $A= $B= $C= $D= L$A= L$B= L$C= L$D=; do echo -n {$i}; done' \
  "{}{}{}{}{L}{L}{L}{L}{}{=}{}{=}{}{=}{}{=}{L}{=}{L}{=}{L}{=}{L}{=}" "" ""

testing "! isn't special" "echo !" "!\n" "" ""
testing "! by itself" '!; echo $?' "1\n" "" ""
testing "! true" '! true; echo $?' "1\n" "" ""
testing "! ! true" '! ! true; echo $?' "0\n" "" ""
testing "! syntax err" '! echo 2>/dev/null < doesnotexist; echo $?' "0\n" "" ""

# The bash man page doesn't say quote removal here, and yet:
testing "case quoting" 'case a in "a") echo hello;; esac' 'hello\n' "" ""

testing "subshell splitting" 'for i in $(true); do echo =$i=; done' "" "" ""
testing "subshell split 2" 'for i in $(echo "one two thr"); do echo =$i=; done'\
  "=one=\n=two=\n=thr=\n" "" ""

# variable assignment argument splitting only performed for "$@"
testing "assignment nosplit" 'X="one two"; Y=$X; echo $Y' "one two\n" "" ""
testing "argument splitting" \
  'chicken() { for i in a"$@"b;do echo =$i=;done;}; chicken 123 456 789' \
  "=a123=\n=456=\n=789b=\n" "" ""
testing "assignment nosplit2" 'pop(){ X="$@";};pop one two three; echo $X' \
  "one two three\n" "" ""

#testing "leading assignments don't affect current line" \
#  'VAR=12345 echo ${VAR}a' "a\n" "" ""
#testing "can't have space before first : but yes around arguments" \
#  'BLAH=abcdefghi; echo ${BLAH: 1 : 3 }' "bcd\n" "" ""

testing "subshell exit err" '(exit 42); echo $?' "42\n" "" ""

# Same thing twice, but how do we cmp if exec exited?
#testing 'exec and $$' testing 'echo $$;exec readlink /proc/self' 

X="$(realpath $(which readlink))"
testing "exec in paren" \
  '(exec readlink /proc/self/exe);echo hello' "$X\nhello\n" "" ""
testing "exec in brackets" \
  "{ exec readlink /proc/self/exe;};echo hi" "$X\n" "" ""

NOSPACE=1 testing "curly brackets and pipe" \
  '{ echo one; echo two ; } | tee blah.txt; wc blah.txt' \
  "one\ntwo\n2 2 8 blah.txt\n" "" ""
NOSPACE=1 testing "parentheses and pipe" \
  '(echo two;echo three)|tee blah.txt;wc blah.txt' \
  "two\nthree\n2 2 10 blah.txt\n" "" ""
testing "pipe into parentheses" \
  'echo hello | (read i <input; echo $i; read i; echo $i)' \
  "there\nhello\n" "there\n" ""

testing "\$''" $'echo $\'abc\\\'def\\nghi\'' "abc'def\nghi\n" '' ''
testing "shift shift" 'shift; shift; shift; echo $? hello' "1 hello\n" "" ""
testing 'search cross $*' 'chicken() { echo ${*/b c/ghi}; }; chicken a b c d' \
  "a b c d\n" "" ""
testing 'eval $IFS' 'IFS=x; X=x; eval abc=a${X}b 2>/dev/null; echo $abc' \
  "\n" '' ''
testing '${@:3:5}' 'chicken() { for i in "${@:3:5}"; do echo =$i=; done; } ; chicken ab cd ef gh ij kl mn op qr' \
  '=ef=\n=gh=\n=ij=\n=kl=\n=mn=\n' '' ''
testing '${@:3:5}' 'chicken() { for i in "${*:3:5}"; do unset IFS; echo =$i=; done; } ; IFS=x chicken ab cd ef gh ij kl mn op qr' \
  '=efxghxijxklxmn=\n' '' ''
testing 'sequence check' 'IFS=x; X=abxcd; echo ${X/bxc/g}' 'agd\n' '' ''

# TODO: The txpect plumbing does not work right yet even on TEST_HOST
#txpect "backtick0" "$SS" "E$P" 'IX=fred; echo `echo \\\\$x`'$'\n' 'Ofred' "E$P" X0
#txpect "backtick1" "$SS" "E$P" 'IX=fred; echo `echo $x`'$'\n' 'Ofred'$'\n' "E$P" X0
#txpect "backtick2" "$SS" "E$P" 'IX=fred; echo `x=y; echo $x`' $'Oy\n' "E$P" X0

shxpect '${ with newline' I$'HELLO=abc; echo ${HELLO/b/\n' E"> " I$'}\n' O$'a c\n'

testing 'here0' 'cat<<<hello' 'hello\n' '' ''
shxpect 'here1' I$'POTATO=123; cat << EOF\n' E"> " \
  I$'$POTATO\n' E"> " I$'EOF\n' O$'123\n'
shxpect 'here2' I$'POTATO=123; cat << E"O"F\n' E"> " \
  I$'$POTATO\n' E"> " I$'EOF\n' O$'$POTATO\n'
testing 'here3' 'abc(){ cat <<< x"$@"yz;};abc one two "three  four"' \
  "xone two three  fouryz\n" "" ""
testing 'here4' 'for i in one two three; do cat <<< "ab${i}de"; done' \
  'abonede\nabtwode\nabthreede\n' '' ''
testing 'here5' $'cat << EOF && cat << EOF2\nEOF2\nEOF\nEOF\nEOF2' \
  'EOF2\nEOF\n' '' ''
# Nothing is actually quoted, but there are quotes, therefore...
testing 'here6' $'cat << EOF""\n$POTATO\nEOF' '$POTATO\n' '' ''
# Not ambiguous when split, unlike <$FILENAME redirects
testing 'here7' 'ABC="abc def"; cat <<< $ABC' 'abc def\n' '' ''
# What does HERE expansion _not_ expand?
testing 'here8' $'ABC="x y"\ncat << EOF\n~root/{"$ABC",def}\nEOF' \
  '~root/{"x y",def}\n' '' ''
testing '<<- eats leading tabs before expansion, but not after' \
  $'A=$\'\\tone\'; cat <<- EOF\n\t\t$A\n\ttwo\nEOF' "\tone\ntwo\n" '' ''

testing '${var}' 'X=abcdef; echo ${X}' 'abcdef\n' '' '' 
testing '${#}' 'X=abcdef; echo ${#X}' "6\n" "" ""
testing 'empty ${}' '{ echo ${};} 2>&1 | grep -o bad' 'bad\n' '' ''
shxpect 'empty ${} syntax err abort' I$'echo ${}; echo hello\n' \
  E I$'echo and\n' O$'and\n'
testing '${$b}' '{ echo ${$b};} 2>&1 | grep -o bad' 'bad\n' '' ''
testing '${!PATH*}' 'echo ${!PATH*}' 'PATH\n' '' ''
testing '${!PATH@}' 'echo ${!PATH@}' 'PATH\n' '' ''
#testing '${!PATH[@]}' 'echo ${!PATH[@]}' '0\n' '' ''
testing '${!x}' 'X=abcdef Y=X; echo ${!Y}' 'abcdef\n' '' ''
testing '${!x@}' 'ABC=def; def=ghi; echo ${!ABC@}' 'ABC\n' '' ''
testing '${!x} err' '{ X=abcdef Y=X:2; echo ${!Y}; echo bang;} 2>/dev/null' \
  '' '' ''
testing '${!x*}' 'abcdef=1 abc=2 abcq=; echo "${!abc@}" | tr " " \\n | sort' \
  'abc\nabcdef\nabcq\n' '' ''
testing '${!x*} none' 'echo "${!abc*}"' '\n' '' ''
testing '${!x*} err' '{ echo "${!abc*x}"; echo boing;} 2>/dev/null' '' '' ''
# TODO bash 5.x broke this
#testing '${!none@Q}' 'echo ${X@Q} ${!X@Q}; X=ABC; echo ${!X@Q}' '\n\n' '' ''
testing '${!x@Q}' 'ABC=123 X=ABC; echo ${!X@Q}' "'123'\n" '' ''
testing '${#@Q}' 'echo ${#@Q}' "'0'\n" '' ''
testing '${!*}' 'xx() { echo ${!*};}; fruit=123; xx fruit' '123\n' '' ''
testing '${!*} indirect' 'xx() { echo ${!a@Q};}; a=@; xx one two three' \
  "'one' 'two' 'three'\n" '' ''
testing '${!x@ } match' \
  '{ ABC=def; def=ghi; echo ${!ABC@ }; } 2>&1 | grep -o bad' 'bad\n' '' ''
# Bash added an error for this between 4.4 and 5.x.
#testing '${!x@ } no match no err' 'echo ${!ABC@ }def' 'def\n' '' ''
testing '${!x@ } no match no err2' 'ABC=def; echo ${!ABC@ }ghi' 'ghi\n' '' ''
toyonly testing '${#x::}' 'ABC=abcdefghijklmno; echo ${#ABC:1:2}' '5\n' '' ''
# TODO: ${!abc@x} does _not_ error? And ${PWD@q}
testing '$""' 'ABC=def; echo $"$ABC"' 'def\n' '' ''
testing '"$""" does not nest' 'echo "$"abc""' '$abc\n' '' ''
testing '${\}}' 'ABC=ab}cd; echo ${ABC/\}/x}' 'abxcd\n' '' ''
testing 'bad ${^}' '{ echo ${^};} 2>&1 | grep -o bad' 'bad\n' '' ''
shxpect '${:} empty len is err' I$'ABC=def; echo ${ABC:}\n' RE'ABC' X
testing '${::} both empty=0' 'ABC=def; echo ${ABC::}' '\n' '' ''
testing '${::} first empty' 'ABC=def; echo ${ABC: : 2 }' 'de\n' '' ''
testing '${::} second empty' 'ABC=def; echo ${ABC: 2 : }' '\n' '' ''
testing '${:}' 'ABC=def; echo ${ABC:1}' 'ef\n' '' ''
testing '${a: }' 'ABC=def; echo ${ABC: 1}' 'ef\n' '' ''
testing '${a :}' 'ABC=def; { echo ${ABC :1};} 2>&1 | grep -o bad' 'bad\n' '' ''
testing '${::}' 'ABC=defghi; echo ${ABC:1:2}' 'ef\n' '' ''
testing '${: : }' 'ABC=defghi; echo ${ABC: 1 : 2 }' 'ef\n' '' ''
testing '${::} indirect' \
  'ABC=defghi:1:2; ( echo ${!ABC};) 2>input; [ -s input ] && echo yes' \
  'yes\n' '' ''
testing '${::-}' 'ABC=defghi; echo ${ABC:1:-2}' 'efg\n' '' ''
testing '${:-:-}' 'ABC=defghi; echo ${ABC:-3:2}' 'defghi\n' '' ''
testing '${:-:-}2' 'echo ${ABC:-3:2}' '3:2\n' '' ''
testing '${: -:}' 'ABC=defghi; echo ${ABC: -3:2}' 'gh\n' '' ''
testing '${@%}' 'chicken() { for i in "${@%abc}"; do echo "=$i="; done;}; chicken 1abc 2abc 3abc' '=1=\n=2=\n=3=\n' '' ''
testing '${*%}' 'chicken() { for i in "${*%abc}"; do echo "=$i="; done;}; chicken 1abc 2abc 3abc' '=1 2 3=\n' '' ''
testing '${@@Q}' 'xx() { echo "${@@Q}"; }; xx one two three' \
  "'one' 'two' 'three'\n" '' ''

shxpect '${/newline/}' I$'x=$\'\na\';echo ${x/\n' E'> ' I$'/b}\n' O$'ba\n' E'> '

shxpect 'line continuation' I$'echo "hello" \\\n' E'> ' I$'> blah\n' E"$P" \
  I$'wc blah\n' O$'1 1 6 blah\n'
shxpect 'line continuation2' I$'echo ABC\\\n' E'> ' I$'DEF\n' O$'ABCDEF\n'
testing "line continuation3" $'ec\\\nho hello' 'hello\n' '' ''
testing "line continuation4" $'if true | \\\n(true);then echo true;fi' 'true\n' '' ''

# Race condition (in bash, but not in toysh) can say 43.
testing 'SECONDS' 'readonly SECONDS=41; sleep 1; echo $SECONDS' '42\n' '' ''
# testing 'SECONDS2' 'readonly SECONDS; SECONDS=0; echo $SECONDS' '' '' '' #bash!
testing 'SECONDS2' 'SECONDS=123+456; echo $SECONDS' '0\n' '' '' #bash!!
testing '$LINENO 2' $'echo $LINENO\necho $LINENO' '0\n1\n' '' ''
testing '$EUID' 'echo $EUID' "$(id -u)\n" '' ''
testing '$UID' 'echo $UID' "$(id -ur)\n" '' ''

testing 'readonly leading assignment' \
  '{ readonly abc=123;abc=def echo hello; echo $?;} 2>output; grep -o readonly output' \
  'hello\n0\nreadonly\n' '' ''
testing 'readonly leading assignment2' \
  'readonly boink=123; export boink; { boink=234 env | grep ^boink=;} 2>/dev/null; echo $?' 'boink=123\n0\n' '' ''
testing 'readonly for' \
  'readonly i; for i in one two three; do echo $i; done 2>/dev/null; echo $?' \
  '1\n' '' ''
testing 'readonly {}<' \
  'readonly i; echo hello 2>/dev/null {i}</dev/null; echo $?' '1\n' '' ''
testing '$_ 1' 'echo walrus; echo $_' 'walrus\nwalrus\n' '' ''
testing '$_ 2' 'unset _; echo $_' '_\n' '' ''

# wildcards

touch walrus wallpapers
testing 'IFS wildcards' \
  'IFS=xy; ABC=abcywal*sxdef; echo $ABC | tr " " "\n" | sort' \
  'abc\ndef\nwallpapers\nwalrus\n' '' ''
rm -f walrus wallpapers

# Force parsing granularity via interactive shxpect because bash parses all
# of sh -c "str" in one go, meaning the "shopt -s extglob" won't take effect
shxpect 'IFS +(extglob)' I$'shopt -s extglob\n' E"$P" \
  I$'IFS=x; ABC=cxd; for i in +($ABC); do echo =$i=; done\n' \
  O$'=+(c=\n' O$'=d)=\n'

touch abc\)d
shxpect 'IFS +(extglob) 2' I$'shopt -s extglob\n' E"$P" \
  I$'ABC="c?d"; for i in ab+($ABC); do echo =$i=; done\n' \
  O$'=abc)d=\n'
rm abc\)d

shxpect '[+(]) overlap priority' I$'shopt -s extglob\n' E"$P" \
  I$'touch "AB[DEF]"; echo AB[+(DEF]) AB[+(DEF)? AB+([DEF)]\n' \
  O$'AB[+(DEF]) AB[DEF] AB+([DEF)]\n' \
  I$'X="("; Y=")"; echo AB[+${X}DEF${Y}?\n' O$'AB[DEF]\n'

# TODO: syntax error takes out ': ${a?b}; echo $?' (I.E. never runs echo)
shxpect '${a?b} sets err, stops cmdline eval' \
  I$': ${a?b} ${c:=d}\n' E E"$P" I$'echo $?$c\n' O$'1\n'

shxpect 'trace redirect' I$'set -x; echo one\n' E$'+ echo one\n'"$P" O$'one\n' \
  I$'echo two 2>/dev/null\n' O$'two\n' E$'+ echo two\n'"$P" \
  I$'{ echo three; } 2>/dev/null\n' O$'three\n' E"$P"
shxpect 'set -u' I$'set -u; echo $walrus\n' REwalrus X

testing 'source file' 'source input' 'hello\n' 'echo hello \\\n' ''
testing '. file' '. input' 'hello\n' 'echo hello \\\n' ''
testing 'source no newline' 'source input' 'hello \\\n' 'echo hello \\' ''
testing 'source is live' \
  'for i in one two three; do echo "echo $i" > input; source input; done' \
  'one\ntwo\nthree\n' 'x' ''
testing 'source is live in functions' \
  'func() { source input; }; for i in one two three; do echo echo $i > input; func; done' \
  'one\ntwo\nthree\n' 'x' ''
testing 'subshell inheritance' \
  'func() { source input; cat <(echo $xx; xx=456; echo $xx); echo $xx;}; echo local xx=123 > input; func; echo $xx' \
  '123\n456\n123\n\n' 'x' ''
testing 'semicolon vs newline' \
  'source input 2>/dev/null || echo yes' 'one\nyes\n' \
  'echo one\necho two; echo |' ''
testing 'syntax err pops to source but encapsulating function continues' \
  'func() { echo one; source <(echo -e "echo hello\necho |") 2>/dev/null; echo three;}; func; echo four' \
  'one\nhello\nthree\nfour\n' '' ''
testing '"exit shell" means exit eval but encapsulating function continues' \
  'func() { eval "echo one; echo \${?potato}; echo and" 2>/dev/null; echo plus;}; func; echo then' \
  'one\nplus\nthen\n' '' ''

shxpect "functions need block" I$'x() echo;\n' RE'[Ss]yntax [Ee]rror' X2
testing 'functions() {} in same PID' \
  '{ echo $BASHPID; chicken() { echo $BASHPID;}; chicken;} | sort -u | wc -l' '1\n' '' ''
testing 'functions() () different PID' \
  '{ echo $BASHPID; chicken() ( echo $BASHPID;); chicken;} | sort -u | wc -l' '2\n' '' ''
testing 'function() just wants any block span' \
  'func() if true; then echo hello; fi; echo one; func; echo two' \
  'one\nhello\ntwo\n' '' ''
testing 'function alternate syntax' \
  'function func if true; then echo hello; fi; echo one; func; echo two' \
  'one\nhello\ntwo\n' '' ''
testing 'function syntax 3' \
  'function func ( ) if true; then echo hello; fi; echo one; func; echo two' \
  'one\nhello\ntwo\n' '' ''
testing 'function nested parentheses' \
  '( potato() { echo aaa; }; potato )' 'aaa\n' '' ''
shxpect 'local creates a whiteout' \
  I$'func() { local potato; echo ${potato?bang}; }; potato=123; func\n' \
  E E"$P" I$'echo $?\n' O$'1\n'
testing 'local replaces/preserves magic type' \
  'x() { local RANDOM=potato; echo $RANDOM;};x;echo -e "$RANDOM\n$RANDOM"|wc -l'\
  'potato\n2\n' '' ''

testing '$$ is parent shell' \
  '{ echo $$; (echo $$) } | sort -u | wc -l' "1\n" "" ""
testing '$PPID is parent shell' \
  '{ echo $PPID; (echo $PPID) } | sort -u | wc -l' "1\n" "" ""
testing '$BASHPID is current PID' \
  '{ echo $BASHPID; (echo $BASHPID) } | sort -u | wc -l' "2\n" "" ""

testing 'unexport supports +=' 'export -n ABC+=DEF; declare -p ABC' \
  'declare -- ABC="DEF"\n' '' ''
testing 'unexport existing +=' \
  'export ABC=XYZ; export -n ABC+=DEF; declare -p ABC' \
  'declare -- ABC="XYZDEF"\n' '' ''

testing '$!' '{ echo $BASHPID & echo $!; echo ${!};} | sort -u | wc -l' '1\n' \
  '' ''

shxpect 'blank line preserves $?' \
  I$'false\n' E"$P" I$'\n' E"$P" I$'echo $?\n' O$'1\n'
testing 'NOP line clears $?' 'false;$NOTHING;echo $?' '0\n' '' ''
testing 'run "$@"' 'false;"$@";echo $?' '0\n' '' ''

# "Word splitting... not performed on the words between the [[ and ]]"
testing '[[split1]]' 'A="1 -lt 2"; [[ $A ]] && echo yes' 'yes\n' '' ''
testing '[[split2]]' 'A="2 -lt 1"; [[ $A ]] && echo yes' 'yes\n' '' ''
testing '[[split3]]' \
  'A="2 -lt 1"; [[ -e $A ]] && echo one; touch "$A" && [[ -e $A ]] && echo two'\
  'two\n' '' ''
rm -f '2 -lt 1'
testing '[[split4]]' \
  '[[ $(cat) == "a b" ]] <<< "a b" > potato && rm potato && echo ok' \
  'ok\n' '' ''
testing '[[split5]]' \
  '[[ $(cat) == "a b" ]] < <(echo a b) > potato && rm potato && echo ok' \
  'ok\n' '' ''
# And token parsing leaking through: 1>2 is an error, 1 >2 is not
testing '[[1>2]] is not a redirect' '[[ 1 >2 ]] || [ -e 2 ] || echo yup' \
  'yup\n' '' ''
testing "[[1 >0]] doesn't need that second space" \
  '[[ 1 >0 ]] && { [ -e 2 ] || echo yup; }' 'yup\n' '' ''
testing '[[1<2]] is alphabetical, not numeric' '[[ 123 < 19 ]] && echo yes' \
  'yes\n' '' ''
testing '[[~]]' '[[ ~ == $HOME ]] && echo yes' 'yes\n' '' ''

testing 'quoting contexts nest' \
        $'echo -n "$(echo "hello $(eval $\'echo -\\\\\\ne \\\'world\\n \\\'\')")"' \
  'hello world\n ' '' ''

# TODO finish variable list from shell init

# $# $? $- $! $0  # $$
# always exported: PWD SHLVL _
#  ./bash -c 'echo $_' prints $BASH, but PATH search shows path? Hmmm...
# ro: UID PPID EUID $
# IFS LINENO
# PATH HOME SHELL USER LOGNAME SHLVL HOSTNAME HOSTTYPE MACHTYPE OSTYPE OLDPWD
# PS0 PS1='$ ' PS2='> ' PS3 PS4 BASH BASH_VERSION
# ENV - if [ -n "$ENV" ]; then . "$ENV"; fi # BASH_ENV - synonym for ENV
# FUNCNEST - maximum function nesting level (abort when above)
# REPLY - set by input with no args
# OPTARG OPTIND - set by getopts builtin
# OPTERR

# maybe not: EXECIGNORE, FIGNORE, GLOBIGNORE

#BASH_SUBSHELL - SHLVL synonym
#BASH_EXECUTION_STRING - -c argument
#
#automatically set:
#OPTARG - set by getopts builtin
#OPTIND - set by getopts builtin
#
#PROMPT_COMMAND PROMPT_DIRTRIM PS0 PS1 PS2 PS3 PS4
#
#unsettable (assignments ignored before then)
#LINENO SECONDS RANDOM
#GROUPS - id -g
#HISTCMD - history number
#
#TMOUT - used by read

# does not match: ./sh -c 'echo {a..Z}' becomes a ` _ ^ ] \ [ Z

# commit ec6639407b9e
#-  IS_TOYBOX_RE='(toybox|This is not GNU).*'
#-  [[ "$IS_TOYBOX" =~ $IS_TOYBOX_RE ]] || SKIPNEXT=1
#+  case "$IS_TOYBOX" in
#+    toybox*) ;;
#+    This\ is\ not\ GNU*) ;;
#+    *) SKIPNEXT=1 ;;
#+  esac

# TODO: categorize tests

# TODO https://mywiki.wooledge.org/BashFAQ
#   http://tiswww.case.edu/php/chet/bash/FAQ
#   https://mywiki.wooledge.org/BashPitfalls#set_-euo_pipefail

#        // ${#} ${#x} ${#@} ${#x[@]} ${#!} ${!#}
#        // ${!} ${!@} ${!@Q} ${!x} ${!x@} ${!x@Q} ${!x#} ${!x[} ${!x[*]}

# Looked like a prefix but wasn't: three chars (@ # -) are both paremeter name
# and slice operator. When immediately followed by } it's parameter, otherwise
# we did NOT have a prefix and it's an operator.
#
# ${#-} ${#-abc}
# ${##} ${##0}
# ${#@} ${#@Q}
#
# backslash not discarded: echo "abc\"def"

# ${x:-y} use default
# ${x:=y} assign default (error if positional)
# ${x:?y} err if null
# ${x:+y} alt value
# ${x:off} ${x:off:len} off<0 from end (must ": -"), len<0 also from end must
#   0-based indexing
# ${@:off:len} positional parameters, off -1 = len, -len is error
#   1-based indexing

# [] wins over +()
# touch 'AB[DEF]'; echo AB[+(DEF]) AB[+(DEF)?
# AB[+(DEF]) AB[DEF]

# Testing shell corner cases _within_ a shell script is kind of hard.