t/chainlint.sed - git - Git at Google


            
            #------------------------------------------------------------------------------

            
            # Detect broken &&-chains in tests.

            
            #

            
            # At present, only &&-chains in subshells are examined by this linter;

            
            # top-level &&-chains are instead checked directly by the test framework. Like

            
            # the top-level &&-chain linter, the subshell linter (intentionally) does not

            
            # check &&-chains within {...} blocks.

            
            #

            
            # Checking for &&-chain breakage is done line-by-line by pure textual

            
            # inspection.

            
            #

            
            # Incomplete lines (those ending with "\") are stitched together with following

            
            # lines to simplify processing, particularly of "one-liner" statements.

            
            # Top-level here-docs are swallowed to avoid false positives within the

            
            # here-doc body, although the statement to which the here-doc is attached is

            
            # retained.

            
            #

            
            # Heuristics are used to detect end-of-subshell when the closing ")" is cuddled

            
            # with the final subshell statement on the same line:

            
            #

            
            #    (cd foo &&

            
            #        bar)

            
            #

            
            # in order to avoid misinterpreting the ")" in constructs such as "x=$(...)"

            
            # and "case $x in *)" as ending the subshell.

            
            #

            
            # Lines missing a final "&&" are flagged with "?!AMP?!", and lines which chain

            
            # commands with ";" internally rather than "&&" are flagged "?!SEMI?!". A line

            
            # may be flagged for both violations.

            
            #

            
            # Detection of a missing &&-link in a multi-line subshell is complicated by the

            
            # fact that the last statement before the closing ")" must not end with "&&".

            
            # Since processing is line-by-line, it is not known whether a missing "&&" is

            
            # legitimate or not until the _next_ line is seen. To accommodate this, within

            
            # multi-line subshells, each line is stored in sed's "hold" area until after

            
            # the next line is seen and processed. If the next line is a stand-alone ")",

            
            # then a missing "&&" on the previous line is legitimate; otherwise a missing

            
            # "&&" is a break in the &&-chain.

            
            #

            
            #    (

            
            #         cd foo &&

            
            #         bar

            
            #    )

            
            #

            
            # In practical terms, when "bar" is encountered, it is flagged with "?!AMP?!",

            
            # but when the stand-alone ")" line is seen which closes the subshell, the

            
            # "?!AMP?!" violation is removed from the "bar" line (retrieved from the "hold"

            
            # area) since the final statement of a subshell must not end with "&&". The

            
            # final line of a subshell may still break the &&-chain by using ";" internally

            
            # to chain commands together rather than "&&", so "?!SEMI?!" is never removed

            
            # from a line (even though "?!AMP?!" might be).

            
            #

            
            # Care is taken to recognize the last _statement_ of a multi-line subshell, not

            
            # necessarily the last textual _line_ within the subshell, since &&-chaining

            
            # applies to statements, not to lines. Consequently, blank lines, comment

            
            # lines, and here-docs are swallowed (but not the command to which the here-doc

            
            # is attached), leaving the last statement in the "hold" area, not the last

            
            # line, thus simplifying &&-link checking.

            
            #

            
            # The final statement before "done" in for- and while-loops, and before "elif",

            
            # "else", and "fi" in if-then-else likewise must not end with "&&", thus

            
            # receives similar treatment.

            
            #

            
            # Swallowing here-docs with arbitrary tags requires a bit of finesse. When a

            
            # line such as "cat <<EOF >out" is seen, the here-doc tag is moved to the front

            
            # of the line enclosed in angle brackets as a sentinel, giving "<EOF>cat >out".

            
            # As each subsequent line is read, it is appended to the target line and a

            
            # (whitespace-loose) back-reference match /^<(.*)>\n\1$/ is attempted to see if

            
            # the content inside "<...>" matches the entirety of the newly-read line. For

            
            # instance, if the next line read is "some data", when concatenated with the

            
            # target line, it becomes "<EOF>cat >out\nsome data", and a match is attempted

            
            # to see if "EOF" matches "some data". Since it doesn't, the next line is

            
            # attempted. When a line consisting of only "EOF" (and possible whitespace) is

            
            # encountered, it is appended to the target line giving "<EOF>cat >out\nEOF",

            
            # in which case the "EOF" inside "<...>" does match the text following the

            
            # newline, thus the closing here-doc tag has been found. The closing tag line

            
            # and the "<...>" prefix on the target line are then discarded, leaving just

            
            # the target line "cat >out".

            
            #

            
            # To facilitate regression testing (and manual debugging), a ">" annotation is

            
            # applied to the line containing ")" which closes a subshell, ">>" to a line

            
            # closing a nested subshell, and ">>>" to a line closing both at once. This

            
            # makes it easy to detect whether the heuristics correctly identify

            
            # end-of-subshell.

            
            #------------------------------------------------------------------------------


            # incomplete line -- slurp up next line

            
            :squash

            
            /\\$/ {

            
            	N

            
            	s/\\\n//

            
            	bsquash

            
            }


            # here-doc -- swallow it to avoid false hits within its body (but keep the

            
            # command to which it was attached)

            
            /<<[ 	]*[-\\'"]*[A-Za-z0-9_]/ {

            
            	s/^\(.*\)<<[ 	]*[-\\'"]*\([A-Za-z0-9_][A-Za-z0-9_]*\)['"]*/<\2>\1<</

            
            	s/[ 	]*<<//

            
            	:hered

            
            	N

            
            	/^<\([^>]*\)>.*\n[ 	]*\1[ 	]*$/!{

            
            		s/\n.*$//

            
            		bhered

            
            	}

            
            	s/^<[^>]*>//

            
            	s/\n.*$//

            
            }


            # one-liner "(...) &&"

            
            /^[ 	]*!*[ 	]*(..*)[ 	]*&&[ 	]*$/boneline


            # same as above but without trailing "&&"

            
            /^[ 	]*!*[ 	]*(..*)[ 	]*$/boneline


            # one-liner "(...) >x" (or "2>x" or "<x" or "|x" or "&"

            
            /^[ 	]*!*[ 	]*(..*)[ 	]*[0-9]*[<>|&]/boneline


            # multi-line "(...\n...)"

            
            /^[ 	]*(/bsubshell


            # innocuous line -- print it and advance to next line

            
            b


            # found one-liner "(...)" -- mark suspect if it uses ";" internally rather than

            
            # "&&" (but not ";" in a string)

            
            :oneline

            
            /;/{

            
            	/"[^"]*;[^"]*"/!s/^/?!SEMI?!/

            
            }

            
            b


            :subshell

            
            # bare "(" line? -- stash for later printing

            
            /^[ 	]*([	]*$/ {

            
            	h

            
            	bnextline

            
            }

            
            # "(..." line -- split off and stash "(", then process "..." as its own line

            
            x

            
            s/.*/(/

            
            x

            
            s/(//

            
            bslurp


            :nextline

            
            N

            
            s/.*\n//


            :slurp

            
            # incomplete line "...\"

            
            /\\$/bicmplte

            
            # multi-line quoted string "...\n..."?

            
            /"/bdqstring

            
            # multi-line quoted string '...\n...'? (but not contraction in string "it's")

            
            /'/{

            
            	/"[^'"]*'[^'"]*"/!bsqstring

            
            }

            
            :folded

            
            # here-doc -- swallow it

            
            /<<[ 	]*[-\\'"]*[A-Za-z0-9_]/bheredoc

            
            # comment or empty line -- discard since final non-comment, non-empty line

            
            # before closing ")", "done", "elsif", "else", or "fi" will need to be

            
            # re-visited to drop "suspect" marking since final line of those constructs

            
            # legitimately lacks "&&", so "suspect" mark must be removed

            
            /^[ 	]*#/bnextline

            
            /^[ 	]*$/bnextline

            
            # in-line comment -- strip it (but not "#" in a string, Bash ${#...} array

            
            # length, or Perforce "//depot/path#42" revision in filespec)

            
            /[ 	]#/{

            
            	/"[^"]*#[^"]*"/!s/[ 	]#.*$//

            
            }

            
            # one-liner "case ... esac"

            
            /^[ 	]*case[ 	]*..*esac/bchkchn

            
            # multi-line "case ... esac"

            
            /^[ 	]*case[ 	]..*[ 	]in/bcase

            
            # multi-line "for ... done" or "while ... done"

            
            /^[ 	]*for[ 	]..*[ 	]in/bcontinue

            
            /^[ 	]*while[ 	]/bcontinue

            
            /^[ 	]*do[ 	]/bcontinue

            
            /^[ 	]*do[ 	]*$/bcontinue

            
            /;[ 	]*do/bcontinue

            
            /^[ 	]*done[ 	]*&&[ 	]*$/bdone

            
            /^[ 	]*done[ 	]*$/bdone

            
            /^[ 	]*done[ 	]*[<>|]/bdone

            
            /^[ 	]*done[ 	]*)/bdone

            
            /||[ 	]*exit[ 	]/bcontinue

            
            /||[ 	]*exit[ 	]*$/bcontinue

            
            # multi-line "if...elsif...else...fi"

            
            /^[ 	]*if[ 	]/bcontinue

            
            /^[ 	]*then[ 	]/bcontinue

            
            /^[ 	]*then[ 	]*$/bcontinue

            
            /;[ 	]*then/bcontinue

            
            /^[ 	]*elif[ 	]/belse

            
            /^[ 	]*elif[ 	]*$/belse

            
            /^[ 	]*else[ 	]/belse

            
            /^[ 	]*else[ 	]*$/belse

            
            /^[ 	]*fi[ 	]*&&[ 	]*$/bdone

            
            /^[ 	]*fi[ 	]*$/bdone

            
            /^[ 	]*fi[ 	]*[<>|]/bdone

            
            /^[ 	]*fi[ 	]*)/bdone

            
            # nested one-liner "(...) &&"

            
            /^[ 	]*(.*)[ 	]*&&[ 	]*$/bchkchn

            
            # nested one-liner "(...)"

            
            /^[ 	]*(.*)[ 	]*$/bchkchn

            
            # nested one-liner "(...) >x" (or "2>x" or "<x" or "|x")

            
            /^[ 	]*(.*)[ 	]*[0-9]*[<>|]/bchkchn

            
            # nested multi-line "(...\n...)"

            
            /^[ 	]*(/bnest

            
            # multi-line "{...\n...}"

            
            /^[ 	]*{/bblock

            
            # closing ")" on own line -- exit subshell

            
            /^[ 	]*)/bclssolo

            
            # "$((...))" -- arithmetic expansion; not closing ")"

            
            /\$(([^)][^)]*))[^)]*$/bchkchn

            
            # "$(...)" -- command substitution; not closing ")"

            
            /\$([^)][^)]*)[^)]*$/bchkchn

            
            # multi-line "$(...\n...)" -- command substitution; treat as nested subshell

            
            /\$([^)]*$/bnest

            
            # "=(...)" -- Bash array assignment; not closing ")"

            
            /=(/bchkchn

            
            # closing "...) &&"

            
            /)[ 	]*&&[ 	]*$/bclose

            
            # closing "...)"

            
            /)[ 	]*$/bclose

            
            # closing "...) >x" (or "2>x" or "<x" or "|x")

            
            /)[ 	]*[<>|]/bclose

            
            :chkchn

            
            # mark suspect if line uses ";" internally rather than "&&" (but not ";" in a

            
            # string and not ";;" in one-liner "case...esac")

            
            /;/{

            
            	/;;/!{

            
            		/"[^"]*;[^"]*"/!s/^/?!SEMI?!/

            
            	}

            
            }

            
            # line ends with pipe "...|" -- valid; not missing "&&"

            
            /|[ 	]*$/bcontinue

            
            # missing end-of-line "&&" -- mark suspect

            
            /&&[ 	]*$/!s/^/?!AMP?!/

            
            :continue

            
            # retrieve and print previous line

            
            x

            
            n

            
            bslurp


            # found incomplete line "...\" -- slurp up next line

            
            :icmplte

            
            N

            
            s/\\\n//

            
            bslurp


            # check for multi-line double-quoted string "...\n..." -- fold to one line

            
            :dqstring

            
            # remove all quote pairs

            
            s/"\([^"]*\)"/@!\1@!/g

            
            # done if no dangling quote

            
            /"/!bdqdone

            
            # otherwise, slurp next line and try again

            
            N

            
            s/\n//

            
            bdqstring

            
            :dqdone

            
            s/@!/"/g

            
            bfolded


            # check for multi-line single-quoted string '...\n...' -- fold to one line

            
            :sqstring

            
            # remove all quote pairs

            
            s/'\([^']*\)'/@!\1@!/g

            
            # done if no dangling quote

            
            /'/!bsqdone

            
            # otherwise, slurp next line and try again

            
            N

            
            s/\n//

            
            bsqstring

            
            :sqdone

            
            s/@!/'/g

            
            bfolded


            # found here-doc -- swallow it to avoid false hits within its body (but keep

            
            # the command to which it was attached)

            
            :heredoc

            
            s/^\(.*\)<<[ 	]*[-\\'"]*\([A-Za-z0-9_][A-Za-z0-9_]*\)['"]*/<\2>\1<</

            
            s/[ 	]*<<//

            
            :heredsub

            
            N

            
            /^<\([^>]*\)>.*\n[ 	]*\1[ 	]*$/!{

            
            	s/\n.*$//

            
            	bheredsub

            
            }

            
            s/^<[^>]*>//

            
            s/\n.*$//

            
            bfolded


            # found "case ... in" -- pass through untouched

            
            :case

            
            x

            
            n

            
            /^[ 	]*esac/bslurp

            
            bcase


            # found "else" or "elif" -- drop "suspect" from final line before "else" since

            
            # that line legitimately lacks "&&"

            
            :else

            
            x

            
            s/?!AMP?!//

            
            x

            
            bcontinue


            # found "done" closing for-loop or while-loop, or "fi" closing if-then -- drop

            
            # "suspect" from final contained line since that line legitimately lacks "&&"

            
            :done

            
            x

            
            s/?!AMP?!//

            
            x

            
            # is 'done' or 'fi' cuddled with ")" to close subshell?

            
            /done.*)/bclose

            
            /fi.*)/bclose

            
            bchkchn


            # found nested multi-line "(...\n...)" -- pass through untouched

            
            :nest

            
            x

            
            :nstslurp

            
            n

            
            # closing ")" on own line -- stop nested slurp

            
            /^[ 	]*)/bnstclose

            
            # comment -- not closing ")" if in comment

            
            /^[ 	]*#/bnstcnt

            
            # "$((...))" -- arithmetic expansion; not closing ")"

            
            /\$(([^)][^)]*))[^)]*$/bnstcnt

            
            # "$(...)" -- command substitution; not closing ")"

            
            /\$([^)][^)]*)[^)]*$/bnstcnt

            
            # closing "...)" -- stop nested slurp

            
            /)/bnstclose

            
            :nstcnt

            
            x

            
            bnstslurp

            
            :nstclose

            
            s/^/>>/

            
            # is it "))" which closes nested and parent subshells?

            
            /)[ 	]*)/bslurp

            
            bchkchn


            # found multi-line "{...\n...}" block -- pass through untouched

            
            :block

            
            x

            
            n

            
            # closing "}" -- stop block slurp

            
            /}/bchkchn

            
            bblock


            # found closing ")" on own line -- drop "suspect" from final line of subshell

            
            # since that line legitimately lacks "&&" and exit subshell loop

            
            :clssolo

            
            x

            
            s/?!AMP?!//

            
            p

            
            x

            
            s/^/>/

            
            b


            # found closing "...)" -- exit subshell loop

            
            :close

            
            x

            
            p

            
            x

            
            s/^/>/

            
            b
	#------------------------------------------------------------------------------
	# Detect broken &&-chains in tests.
	#
	# At present, only &&-chains in subshells are examined by this linter;
	# top-level &&-chains are instead checked directly by the test framework. Like
	# the top-level &&-chain linter, the subshell linter (intentionally) does not
	# check &&-chains within {...} blocks.
	#
	# Checking for &&-chain breakage is done line-by-line by pure textual
	# inspection.
	#
	# Incomplete lines (those ending with "\") are stitched together with following
	# lines to simplify processing, particularly of "one-liner" statements.
	# Top-level here-docs are swallowed to avoid false positives within the
	# here-doc body, although the statement to which the here-doc is attached is
	# retained.
	#
	# Heuristics are used to detect end-of-subshell when the closing ")" is cuddled
	# with the final subshell statement on the same line:
	#
	# (cd foo &&
	# bar)
	#
	# in order to avoid misinterpreting the ")" in constructs such as "x=$(...)"
	# and "case $x in *)" as ending the subshell.
	#
	# Lines missing a final "&&" are flagged with "?!AMP?!", and lines which chain
	# commands with ";" internally rather than "&&" are flagged "?!SEMI?!". A line
	# may be flagged for both violations.
	#
	# Detection of a missing &&-link in a multi-line subshell is complicated by the
	# fact that the last statement before the closing ")" must not end with "&&".
	# Since processing is line-by-line, it is not known whether a missing "&&" is
	# legitimate or not until the _next_ line is seen. To accommodate this, within
	# multi-line subshells, each line is stored in sed's "hold" area until after
	# the next line is seen and processed. If the next line is a stand-alone ")",
	# then a missing "&&" on the previous line is legitimate; otherwise a missing
	# "&&" is a break in the &&-chain.
	#
	# (
	# cd foo &&
	# bar
	# )
	#
	# In practical terms, when "bar" is encountered, it is flagged with "?!AMP?!",
	# but when the stand-alone ")" line is seen which closes the subshell, the
	# "?!AMP?!" violation is removed from the "bar" line (retrieved from the "hold"
	# area) since the final statement of a subshell must not end with "&&". The
	# final line of a subshell may still break the &&-chain by using ";" internally
	# to chain commands together rather than "&&", so "?!SEMI?!" is never removed
	# from a line (even though "?!AMP?!" might be).
	#
	# Care is taken to recognize the last _statement_ of a multi-line subshell, not
	# necessarily the last textual _line_ within the subshell, since &&-chaining
	# applies to statements, not to lines. Consequently, blank lines, comment
	# lines, and here-docs are swallowed (but not the command to which the here-doc
	# is attached), leaving the last statement in the "hold" area, not the last
	# line, thus simplifying &&-link checking.
	#
	# The final statement before "done" in for- and while-loops, and before "elif",
	# "else", and "fi" in if-then-else likewise must not end with "&&", thus
	# receives similar treatment.
	#
	# Swallowing here-docs with arbitrary tags requires a bit of finesse. When a
	# line such as "cat <<EOF >out" is seen, the here-doc tag is moved to the front
	# of the line enclosed in angle brackets as a sentinel, giving "<EOF>cat >out".
	# As each subsequent line is read, it is appended to the target line and a
	# (whitespace-loose) back-reference match /^<(.*)>\n\1$/ is attempted to see if
	# the content inside "<...>" matches the entirety of the newly-read line. For
	# instance, if the next line read is "some data", when concatenated with the
	# target line, it becomes "<EOF>cat >out\nsome data", and a match is attempted
	# to see if "EOF" matches "some data". Since it doesn't, the next line is
	# attempted. When a line consisting of only "EOF" (and possible whitespace) is
	# encountered, it is appended to the target line giving "<EOF>cat >out\nEOF",
	# in which case the "EOF" inside "<...>" does match the text following the
	# newline, thus the closing here-doc tag has been found. The closing tag line
	# and the "<...>" prefix on the target line are then discarded, leaving just
	# the target line "cat >out".
	#
	# To facilitate regression testing (and manual debugging), a ">" annotation is
	# applied to the line containing ")" which closes a subshell, ">>" to a line
	# closing a nested subshell, and ">>>" to a line closing both at once. This
	# makes it easy to detect whether the heuristics correctly identify
	# end-of-subshell.
	#------------------------------------------------------------------------------

	# incomplete line -- slurp up next line
	:squash
	/\\$/ {
	N
	s/\\\n//
	bsquash
	}

	# here-doc -- swallow it to avoid false hits within its body (but keep the
	# command to which it was attached)
	/<<[ ][-\\'"][A-Za-z0-9_]/ {
	s/^\(.\)<<[ ][-\\'"]\([A-Za-z0-9_][A-Za-z0-9_]\)['"]*/<\2>\1<</
	s/[ ]*<<//
	:hered
	N
	/^<\([^>]\)>.\n[ ]\1[ ]$/!{
	s/\n.*$//
	bhered
	}
	s/^<[^>]*>//
	s/\n.*$//
	}

	# one-liner "(...) &&"
	/^[ ]![ ](..)[ ]&&[ ]$/boneline

	# same as above but without trailing "&&"
	/^[ ]![ ](..)[ ]*$/boneline

	# one-liner "(...) >x" (or "2>x" or "<x" or "\|x" or "&"
	/^[ ]![ ](..)[ ][0-9][<>\|&]/boneline

	# multi-line "(...\n...)"
	/^[ ]*(/bsubshell

	# innocuous line -- print it and advance to next line
	b

	# found one-liner "(...)" -- mark suspect if it uses ";" internally rather than
	# "&&" (but not ";" in a string)
	:oneline
	/;/{
	/"[^"];[^"]"/!s/^/?!SEMI?!/
	}
	b

	:subshell
	# bare "(" line? -- stash for later printing
	/^[ ]([ ]$/ {
	h
	bnextline
	}
	# "(..." line -- split off and stash "(", then process "..." as its own line
	x
	s/.*/(/
	x
	s/(//
	bslurp

	:nextline
	N
	s/.*\n//

	:slurp
	# incomplete line "...\"
	/\\$/bicmplte
	# multi-line quoted string "...\n..."?
	/"/bdqstring
	# multi-line quoted string '...\n...'? (but not contraction in string "it's")
	/'/{
	/"[^'"]'[^'"]"/!bsqstring
	}
	:folded
	# here-doc -- swallow it
	/<<[ ][-\\'"][A-Za-z0-9_]/bheredoc
	# comment or empty line -- discard since final non-comment, non-empty line
	# before closing ")", "done", "elsif", "else", or "fi" will need to be
	# re-visited to drop "suspect" marking since final line of those constructs
	# legitimately lacks "&&", so "suspect" mark must be removed
	/^[ ]*#/bnextline
	/^[ ]*$/bnextline
	# in-line comment -- strip it (but not "#" in a string, Bash ${#...} array
	# length, or Perforce "//depot/path#42" revision in filespec)
	/[ ]#/{
	/"[^"]#[^"]"/!s/[ ]#.*$//
	}
	# one-liner "case ... esac"
	/^[ ]case[ ]..*esac/bchkchn
	# multi-line "case ... esac"
	/^[ ]case[ ]..[ ]in/bcase
	# multi-line "for ... done" or "while ... done"
	/^[ ]for[ ]..[ ]in/bcontinue
	/^[ ]*while[ ]/bcontinue
	/^[ ]*do[ ]/bcontinue
	/^[ ]do[ ]$/bcontinue
	/;[ ]*do/bcontinue
	/^[ ]done[ ]&&[ ]*$/bdone
	/^[ ]done[ ]$/bdone
	/^[ ]done[ ][<>\|]/bdone
	/^[ ]done[ ])/bdone
	/\|\|[ ]*exit[ ]/bcontinue
	/\|\|[ ]exit[ ]$/bcontinue
	# multi-line "if...elsif...else...fi"
	/^[ ]*if[ ]/bcontinue
	/^[ ]*then[ ]/bcontinue
	/^[ ]then[ ]$/bcontinue
	/;[ ]*then/bcontinue
	/^[ ]*elif[ ]/belse
	/^[ ]elif[ ]$/belse
	/^[ ]*else[ ]/belse
	/^[ ]else[ ]$/belse
	/^[ ]fi[ ]&&[ ]*$/bdone
	/^[ ]fi[ ]$/bdone
	/^[ ]fi[ ][<>\|]/bdone
	/^[ ]fi[ ])/bdone
	# nested one-liner "(...) &&"
	/^[ ](.)[ ]&&[ ]$/bchkchn
	# nested one-liner "(...)"
	/^[ ](.)[ ]*$/bchkchn
	# nested one-liner "(...) >x" (or "2>x" or "<x" or "\|x")
	/^[ ](.)[ ][0-9][<>\|]/bchkchn
	# nested multi-line "(...\n...)"
	/^[ ]*(/bnest
	# multi-line "{...\n...}"
	/^[ ]*{/bblock
	# closing ")" on own line -- exit subshell
	/^[ ]*)/bclssolo
	# "$((...))" -- arithmetic expansion; not closing ")"
	/\$(([^)][^)]))[^)]$/bchkchn
	# "$(...)" -- command substitution; not closing ")"
	/\$([^)][^)])[^)]$/bchkchn
	# multi-line "$(...\n...)" -- command substitution; treat as nested subshell
	/\$([^)]*$/bnest
	# "=(...)" -- Bash array assignment; not closing ")"
	/=(/bchkchn
	# closing "...) &&"
	/)[ ]&&[ ]$/bclose
	# closing "...)"
	/)[ ]*$/bclose
	# closing "...) >x" (or "2>x" or "<x" or "\|x")
	/)[ ]*[<>\|]/bclose
	:chkchn
	# mark suspect if line uses ";" internally rather than "&&" (but not ";" in a
	# string and not ";;" in one-liner "case...esac")
	/;/{
	/;;/!{
	/"[^"];[^"]"/!s/^/?!SEMI?!/
	}
	}
	# line ends with pipe "...\|" -- valid; not missing "&&"
	/\|[ ]*$/bcontinue
	# missing end-of-line "&&" -- mark suspect
	/&&[ ]*$/!s/^/?!AMP?!/
	:continue
	# retrieve and print previous line
	x
	n
	bslurp

	# found incomplete line "...\" -- slurp up next line
	:icmplte
	N
	s/\\\n//
	bslurp

	# check for multi-line double-quoted string "...\n..." -- fold to one line
	:dqstring
	# remove all quote pairs
	s/"\([^"]*\)"/@!\1@!/g
	# done if no dangling quote
	/"/!bdqdone
	# otherwise, slurp next line and try again
	N
	s/\n//
	bdqstring
	:dqdone
	s/@!/"/g
	bfolded

	# check for multi-line single-quoted string '...\n...' -- fold to one line
	:sqstring
	# remove all quote pairs
	s/'\([^']*\)'/@!\1@!/g
	# done if no dangling quote
	/'/!bsqdone
	# otherwise, slurp next line and try again
	N
	s/\n//
	bsqstring
	:sqdone
	s/@!/'/g
	bfolded

	# found here-doc -- swallow it to avoid false hits within its body (but keep
	# the command to which it was attached)
	:heredoc
	s/^\(.\)<<[ ][-\\'"]\([A-Za-z0-9_][A-Za-z0-9_]\)['"]*/<\2>\1<</
	s/[ ]*<<//
	:heredsub
	N
	/^<\([^>]\)>.\n[ ]\1[ ]$/!{
	s/\n.*$//
	bheredsub
	}
	s/^<[^>]*>//
	s/\n.*$//
	bfolded

	# found "case ... in" -- pass through untouched
	:case
	x
	n
	/^[ ]*esac/bslurp
	bcase

	# found "else" or "elif" -- drop "suspect" from final line before "else" since
	# that line legitimately lacks "&&"
	:else
	x
	s/?!AMP?!//
	x
	bcontinue

	# found "done" closing for-loop or while-loop, or "fi" closing if-then -- drop
	# "suspect" from final contained line since that line legitimately lacks "&&"
	:done
	x
	s/?!AMP?!//
	x
	# is 'done' or 'fi' cuddled with ")" to close subshell?
	/done.*)/bclose
	/fi.*)/bclose
	bchkchn

	# found nested multi-line "(...\n...)" -- pass through untouched
	:nest
	x
	:nstslurp
	n
	# closing ")" on own line -- stop nested slurp
	/^[ ]*)/bnstclose
	# comment -- not closing ")" if in comment
	/^[ ]*#/bnstcnt
	# "$((...))" -- arithmetic expansion; not closing ")"
	/\$(([^)][^)]))[^)]$/bnstcnt
	# "$(...)" -- command substitution; not closing ")"
	/\$([^)][^)])[^)]$/bnstcnt
	# closing "...)" -- stop nested slurp
	/)/bnstclose
	:nstcnt
	x
	bnstslurp
	:nstclose
	s/^/>>/
	# is it "))" which closes nested and parent subshells?
	/)[ ]*)/bslurp
	bchkchn

	# found multi-line "{...\n...}" block -- pass through untouched
	:block
	x
	n
	# closing "}" -- stop block slurp
	/}/bchkchn
	bblock

	# found closing ")" on own line -- drop "suspect" from final line of subshell
	# since that line legitimately lacks "&&" and exit subshell loop
	:clssolo
	x
	s/?!AMP?!//
	p
	x
	s/^/>/
	b

	# found closing "...)" -- exit subshell loop
	:close
	x
	p
	x
	s/^/>/
	b