АВК

Использование GNU awk или mawk:

$ awk '$1~"^"word{printf("--\n%s",$0)}' word='are' RS='--\n' infile
--
are you happy
--
are(you hungry
too

Это устанавливает слово переменной равным слову, которое должно соответствовать в начале записи, а разделитель записей RS ()равен ' --', за которым следует новая строка \n. Потом,для любой записи, начинающейся со слова, совпадающего с ($1~"^"word), выведите отформатированную запись. Формат начинается с '--' с новой строкой с точной найденной записью.

ГРЭП

Использование (GNU для опции -z)grep:

grep -Pz -- '--\nare(?:[^\n]*\n)+?(?=--|\Z)' infile
grep -Pz -- '(?s)--\nare.*?(?=\n--|\Z)\n' infile
grep -Pz -- '(?s)--\nare(?:(?!\n--).)*\n' infile

Описание (с )Для следующих описаний опция PCRE (?x)используется для добавления (большого количества )поясняющих комментариев (и пробелов ), встроенных в реальное (рабочее )регулярное выражение. Если удалить комментарии (и большинство пробелов)(до следующей новой строки ), результирующая строка останется тем же регулярным выражением. Это позволяет подробно описать регулярное выражение в рабочем коде. Это значительно упрощает обслуживание кода.

Вариант 1 регулярного выражения(?x)--\nare(?:[^\n]*\n)+?(?=--|\Z)

(?x)   # match the remainder of the pattern with the following
       # effective flags: x
       #      x modifier: extended. Spaces and text after a # 
       #      in the pattern are ignored
--     # matches the characters -- literally (case sensitive)
\n     # matches a line-feed (newline) character (ASCII 10)
are    # matches the characters are literally (case sensitive)
(?:    #      Non-Capturing Group (?:[^\n]*\n)+?
[^\n]  #           matches non-newline characters
*      #           Quantifier — Matches between zero and unlimited times, as
       #           many times as possible, giving back as needed (greedy)
\n     #           matches a line-feed (newline) character (ASCII 10)
)      #      Close the Non-Capturing Group
+?     # Quantifier — Matches between one and unlimited times, as
       # few times as possible, expanding as needed (lazy)
       # A repeated capturing group will only capture the last iteration.
       # Put a capturing group around the repeated group to capture all
       # iterations or use a non-capturing group instead if you're not
       # interested in the data
(?=    # Positive Lookahead (?=--|\Z)
       # Assert that the Regex below matches
       #      1st Alternative --
--     #           matches the characters -- literally (case sensitive)
|      #      2nd Alternative \Z
\Z     #           \Z asserts position at the end of the string, or before
       #           the line terminator right at the end of the 
       #           string (if any)
)      #      Closing the lookahead.

Вариант 2 регулярного выражения(?sx)--\nare.*?(?=\n--|\Z)\n

(?sx)  # match the remainder of the pattern with the following eff. flags: sx
       #        s modifier: single line. Dot matches newline characters
       #        x modifier: extended. Spaces and text after a # in 
       #        the pattern are ignored
--     # matches the characters -- literally (case sensitive)
\n     # matches a line-feed (newline) character (ASCII 10)
are    # matches the characters are literally (case sensitive)
.*?    # matches any character 
       #        Quantifier — Matches between zero and unlimited times,
       #        as few times as possible, expanding as needed (lazy).
(?=    # Positive Lookahead (?=\n--|\Z)
       # Assert that the Regex below matches
       #        1st Alternative \n--
\n     #               matches a line-feed (newline) character (ASCII 10)
--     #               matches the characters -- literally.
|      #        2nd Alternative \Z
\Z     #               \Z asserts position at the end of the string, or
       #               before the line terminator right at
       #               the end of the string (if any)
)      # Close the lookahead parenthesis.
\n     #        matches a line-feed (newline) character (ASCII 10)
 

Вариант 3 регулярного выражения(?xs)--\nare(?:(?!\n--).)*\n

(?xs)  # match the remainder of the pattern with the following eff. flags: xs
       # modifier x : extended. Spaces and text after a # in are ignored
       # modifier s : single line. Dot matches newline characters
--     # matches the characters -- literally (case sensitive)
\n     # matches a line-feed (newline) character (ASCII 10)
are    # matches the characters are literally (case sensitive)
(?:    # Non-capturing group (?:(?!\n--).)
(?!    #      Negative Lookahead (?!\n--)
       #           Assert that the Regex below does not match
\n     #                matches a line-feed (newline) character (ASCII 10)
--     #                matches the characters -- literally
)      #      Close Negative lookahead
.      #      matches any character
)      # Close the Non-Capturing group.
*      # Quantifier — Matches between zero and unlimited times, as many
       # times as possible, giving back as needed (greedy)
\n     # matches a line-feed (newline) character (ASCII 10)

сед

$ sed -nEe 'bend
            :start  ;N;/^--\nare/!b
            :loop   ;/^--$/!{p;n;bloop}
            :end    ;/^--$/bstart'           infile