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Top Forums Shell Programming and Scripting awk - Multi-line data to be stored in variable Post 302971477 by Scrutinizer on Wednesday 20th of April 2016 04:00:18 PM
Old 04-20-2016
Interesting. I had a look at this and it appears this behavior is with any character, not just "@", but also for "*", "a" or "b".

I only saw this with AIX and HPUX awk..

A possible explanation for the difference between [@] and @ may be that in the POSIX specification when a single character is used as FS, then this is regarded as a string and not as a regular expression. When [c] is used (where c is a character, for example @) then this is a regular expression.

In these two awks, it appears that, if an RS other than\n is used, and a single character is used as FS then a newline is still seen as a field separator, whereas this is not the case if FS is a regular expression.

I could not find anything in the POSIX specification that describes this behavior, so it is not as it should be. It does remind me a bit of how newlines are field separators irrespective of FS value when RS="" is used, so maybe it is a remnant behavior of some sort.

Last edited by Scrutinizer; 04-20-2016 at 07:29 PM..
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REGEXP(6)							   Games Manual 							 REGEXP(6)

NAME
regexp - regular expression notation DESCRIPTION
A regular expression specifies a set of strings of characters. A member of this set of strings is said to be matched by the regular expression. In many applications a delimiter character, commonly bounds a regular expression. In the following specification for regular expressions the word `character' means any character (rune) but newline. The syntax for a regular expression e0 is e3: literal | charclass | '.' | '^' | '$' | '(' e0 ')' e2: e3 | e2 REP REP: '*' | '+' | '?' e1: e2 | e1 e2 e0: e1 | e0 '|' e1 A literal is any non-metacharacter, or a metacharacter (one of .*+?[]()|^$), or the delimiter preceded by A charclass is a nonempty string s bracketed [s] (or [^s]); it matches any character in (or not in) s. A negated character class never matches newline. A substring a-b, with a and b in ascending order, stands for the inclusive range of characters between a and b. In s, the metacharacters an initial and the regular expression delimiter must be preceded by a other metacharacters have no special meaning and may appear unescaped. A matches any character. A matches the beginning of a line; matches the end of the line. The REP operators match zero or more (*), one or more (+), zero or one (?), instances respectively of the preceding regular expression e2. A concatenated regular expression, e1e2, matches a match to e1 followed by a match to e2. An alternative regular expression, e0|e1, matches either a match to e0 or a match to e1. A match to any part of a regular expression extends as far as possible without preventing a match to the remainder of the regular expres- sion. SEE ALSO
awk(1), ed(1), sam(1), sed(1), regexp(2) REGEXP(6)
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