Shell Programming and Scripting

I think your regular expression is correct.
It uses perl extensions, and I see that some perl extensions have found their way into the Linux RE and ERE

Code:

# grep '\s\s\s' file
this.something    =='something'.that
this.something    == 'something'.that
this.something    ==    'something'.that
egrep '\s\s\s' file
this.something    =='something'.that
this.something    == 'something'.that
this.something    ==    'something'.that

Is this compliant with standards? Don, your valuable opinion?

I stick to perl for demonstration.
Your problem might be embedded perl/sed/grep code.
Within 'embedded' code you need to escape a ' as '\''.

Code:

perl -lne '/(\w+)\s*(==)\s*(['\''"]?\w+["'\'']?)/ and print' file

Perl even allows to print the match in each ( )

Code:

perl -lne '/(\w+)\s*(==)\s*(['\''"]?\w+["'\'']?)/ and print "($1) ($2) ($3)"' file

No it is not. The standard doesn't use or mention perl REs in general nor \s in particular.

Utilities in the standard using basic REs (AKA BREs) such as grep (without -F and -E), ed, ex, and sed don't even have the common C backslash escapes in REs. Except for awk and lex, the same is true for utilities in the standard using extended REs (AKA EREs). The awk and lex utilities do require that the C escapes for the alert (\a), backspace (\b), form feed (\f), new line (\n), carriage return (\r), tab (\t), and vertical tab (\v) characters be recognized in EREs. In all other utilities, the standard assumes that the literal characters (rather than backslash escape representations of them) will be used in REs. The standard also allows use of character class expressions (e.g., [[:space:]]).

True I'm sorry.

Adding [[:space::]] worked just fine.

Many thanks.

Hi @MadeInGermany,

Thanks for your inputs.