#!/bin/echo no
# 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
# ${@:off:len} positional parameters, off -1 = len, -len is error
# 1-based indexing
# [] wins over +()
# touch 'AB[DEF]'; echo AB[+(DEF]) AB[+(DEF)?
# AB[+(DEF]) AB[DEF]
# Testing shell corner cases _within_ a shell script is kind of hard.
[ -f testing.sh ] && . testing.sh
# TODO make fake pty wrapper for test infrastructure
#testing "name" "command" "result" "infile" "stdin"
# texpect "name" "command" E/O/I"string"
# Use "bash" name for host, "sh" for toybox
[ -z "$SH" ] && { [ -z "$TEST_HOST" ] && SH="sh" || export SH="bash" ; }
# Prompt changes for root/normal user
[ $(id -u) -eq 0 ] && P='# ' || P='$ '
# run sufficiently isolated shell child process to get predictable results
SS="env -i PATH=${PATH@Q} PS1='\\$ ' $SH --noediting --noprofile --norc -is"
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"$P"
shxpect "redirect err" I$'echo > /dev/full\n' E E"$P"
shxpect "wait for <(exit)" I$'cat <(echo hello 1>&2)\n' E$'hello\n' E"$P"
# Test the sh -c stuff 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 "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' '' ''
# 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+$1\n\nexit 42' ''
testing '$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" \
"" ""
testing 'default exports' \
"env -i \"$(which $SH)\" --noprofile --norc -c env | sort" \
"PWD=$(pwd)\nSHLVL=1\n_=$(which env)\n" "" ""
testing "leading assignment fail" \
"{ \$SH -c 'X=\${a?blah} > walroid';ls walroid;} 2>/dev/null" '' '' ''
#########################################################################
# Change EVAL to call sh -c for us, using "bash" explicitly for the host.
export EVAL="$SH -c"
testing "smoketest" "echo hello" "hello\n" "" ""
testing "line break" $'ec\\\nho hello' 'hello\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" "" ""
# 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 $( out 2>/does/not/exist\n' E E"$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}A variable occurred
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 "$X"' 'a b c d e\n' '' ''
testing "leading assignment fail2" \
"{ 1blah=123 echo hello;} 2>/dev/null || echo no" "no\n" "" ""
testing "leading assignment redirect" \
"blah=123 echo hello > walrus && ls walrus" "walrus\n" "" ""
rm -f walrus
testing "{1..5}" "echo {1..5}" "1 2 3 4 5\n" "" ""
testing "{5..1}" "echo {5..1}" "5 4 3 2 1\n" "" ""
testing "{5..1..2}" "echo {5..1..2}" "5 3 1\n" "" ""
testing "{a..z..-3}" "echo {a..z..-3}" "a d g j m p s v y\n" "" ""
testing 'background pipe block' \
'if true; then { sleep .25;bzcat "$FILES"/blkid/ntfs.bz2; }& fi | wc -c' \
'8388608\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 '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"
# 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 /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$'a c\n'
shxpect 'here1' I$'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"$@"yz;};abc one two "three four"' \
"xone two three fouryz\n" "" ""
testing '${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 "${!abc*x}"; echo boing;} 2>/dev/null' '' '' ''
testing '${!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 ${!ABC@ }; } 2>&1 | grep -o bad' 'bad\n' '' ''
testing '${!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 ${^};} 2>&1 | grep -o bad' 'bad\n' '' ''
testing '${:}' '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 ${!ABC};} 2>&1 | grep -o bad' \
'bad\n' '' ''
testing '${::-}' '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'
# 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 $?' \
'1\n' '' ''
testing 'readonly {}<' \
'readonly i; echo hello 2>/dev/null {i} ' PS3 PS4 BASH BASH_VERSION
# ENV - if [ -n "$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
#BASHPID - synonym for $$ HERE
#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