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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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REGEX(3)						     Library Functions Manual							  REGEX(3)

NAME
re_comp, re_exec - regular expression handler SYNOPSIS
char *re_comp(s) char *s; re_exec(s) char *s; DESCRIPTION
Re_comp compiles a string into an internal form suitable for pattern matching. Re_exec checks the argument string against the last string passed to re_comp. Re_comp returns 0 if the string s was compiled successfully; otherwise a string containing an error message is returned. If re_comp is passed 0 or a null string, it returns without changing the currently compiled regular expression. Re_exec returns 1 if the string s matches the last compiled regular expression, 0 if the string s failed to match the last compiled regular expression, and -1 if the compiled regular expression was invalid (indicating an internal error). The strings passed to both re_comp and re_exec may have trailing or embedded newline characters; they are terminated by nulls. The regular expressions recognized are described in the manual entry for ed(1), given the above difference. SEE ALSO
ed(1), ex(1), egrep(1), fgrep(1), grep(1) DIAGNOSTICS
Re_exec returns -1 for an internal error. Re_comp returns one of the following strings if an error occurs: No previous regular expression, Regular expression too long, unmatched (, missing ], too many () pairs, unmatched ). 3rd Berkeley Distribution May 15, 1985 REGEX(3)
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