"open" range operator

[RjY]

Summary: The "flip-flop" sed/awk-style range operator includes its end
points. I would like to know if there's a way to make it not do that.

To illustrate[1], suppose I have a file like this:

blah
START
bleourgh
END
fleurgh

then feeding it into perl -ne 'print if /START/../END/;' gives

START
bleourgh
END

What I would like is a range operator suitable for shell one-liners that
does the same but is false on the endpoints rather than true, so that
the above example would not include the endpoints and so simply print
"bleourgh".

Is there a short idiom for this that I have simply missed? It seems not
to be too exotic a use-case. I tried using ... instead of .. but it had
no effect (obviously I misunderstood the difference)

[1] for the mathematically inclined: the range operator works more like
a closed interval; I would like it to work like an open one.

 

[sln]

Summary: The "flip-flop" sed/awk-style range operator includes its end
points. I would like to know if there's a way to make it not do that.

To illustrate[1], suppose I have a file like this:

blah
START
bleourgh
END
fleurgh

then feeding it into perl -ne 'print if /START/../END/;' gives

START
bleourgh
END

What I would like is a range operator suitable for shell one-liners that
does the same but is false on the endpoints rather than true, so that
the above example would not include the endpoints and so simply print
"bleourgh".

Is there a short idiom for this that I have simply missed? It seems not
to be too exotic a use-case. I tried using ... instead of .. but it had
no effect (obviously I misunderstood the difference)

[1] for the mathematically inclined: the range operator works more like
a closed interval; I would like it to work like an open one.

This probably works. Same principle to check the return sequence 'string'
in scalar context:

print if ((/START/../END/) =~ /^(?:1\d+|[2-9]\d*)$/);

-sln

-------------------
use strict;
use warnings;

while (<DATA>)
{
print if ((/START/../END/) =~ /^(?:1\d+|[2-9]\d*)$/);
}

__DATA__

blah

blah
START
bleourgh
END
fleurgh

START
1
2
3
4
5
/(^1|E0)$/
6
7
8
9
/ \d
0
1
2
3
4
5
6
7
8
9
0
bleourgh
before
END
fleurgh

END

then feeding it into perl -ne 'print if /START/.
1
2
hello
3
4
../END/;' gives


END

asdf

then feeding it into perl -ne 'print if /START/../END/;' gives


abdsfasdg

 

[C.DeRykus]

It is ugly, but you can examine the flip-flop's return value:

    print if /START/../END/ and (/START/../END/) !~ /(^1|E0)$/
or
    $ff = /START/../END/; print if $ff and $ff !~ /(^1|E0)$/

or perhaps the magic-challenged might prefer:

$ff = /START/../END/;
print if $ff>1 and $ff =~ /^\d+$/;

 

[sln]

What I would like is a range operator suitable for shell one-liners that
does the same but is false on the endpoints rather than true, so that
the above example would not include the endpoints and so simply print
"bleourgh".

This probably works. Same principle to check the return sequence 'string'
in scalar context:

print if ((/START/../END/) =~ /^(?:1\d+|[2-9]\d*)$/);

I guess you could extrapolate this to cover all possible ranges:

# Start - End
print if (/START/../END/);

# not Start - not End
print if ((/START/../END/) =~ /^(?:1\d+|[2-9]\d*)$/);

# Start - not End
print if ((/START/../END/) =~ /^(?:[1-9]\d*)$/);

# not Start - End
print if ((/START/../END/) =~ /^(?:1\d+|[2-9]\d*)(?:E0)?$/);

-sln

 

[RjY]

Tad McClellan posted:

It is ugly, but you can examine the flip-flop's return value:

print if /START/../END/ and (/START/../END/) !~ /(^1|E0)$/
or
$ff = /START/../END/; print if $ff and $ff !~ /(^1|E0)$/

Thank you, this will do fine

Thanks to all who answered.