Grepping second pattern after matching first pattern - regex

Question

Is there any grep/sed option which will allow me to match a pattern after matching another pattern? For example: Input file (foos are variable patterns starting with 0 mixed with random numbers preceded by # in front):
0foo1
0foo2
0foo3
\#89888
0foo4
0foo5
\#98980
0foo6
So once I try to search for a variable pattern (eg. foo2), I also want to match another pattern (eg, #number) from this pattern line number, in this case, #89888.
Therefore output for variable foo2 must be:
foo2 #89888
For variable foo5:
foo5 #98980
foos consist of every character, including which may be considered metacharacters.
I tried a basic regex match script using tcl which will first search for foo* and then search for next immediate #, but since I am working with a very large file, it will take days to finish. Any help is appreciated.

Answer 1

A Perl one-liner to slurp the whole file and match across any newlines for the pattern you seek would look like:
perl -000 -nle 'm{(foo2).*(\#89888)}s and print join " ",$1,$2' file
The -000 switch enables "slurp" mode which signals Perl not to split the file into chunks, but rather treat it as one large string. The s modifier lets . match any character, including a newline.

Answer 2

#!/usr/bin/perl
use strict;
use warnings;
use Data::Dumper;
my ( %matches, $recent_foo );
while(<DATA>)
{
chomp;
( $matches{$recent_foo} ) = $1 if m/(\\#\d+)/;
( $recent_foo ) = $1 if m/(0foo\d+)/;
}
print Dumper( \%matches );
__DATA__
0foo1
0foo2
0foo3
\#89888
0foo4
0foo5
\#98980
0foo6
./perl
$VAR1 = {
'0foo5' => '\\#98980',
'0foo3' => '\\#89888'
};

Answer 3

If what you want is 0foo1, 0foo2 and 0foo3 to all have the same value the following will do:
#!/usr/bin/perl
use strict;
use warnings;
use Data::Dumper;
my ( %matches, #recent_foo );
while(<DATA>)
{
chomp;
if (/^\\#/)
{
#matches{#recent_foo} = ($') x #recent_foo;
undef #recent_foo;
}
elsif (/^0/)
{
push #recent_foo, $';
}
}
print Dumper( \%matches );
__DATA__
0foo1
0foo2
0foo3
\#89888
0foo4
0foo5
\#98980
0foo6
gives:
$VAR1 = {
'foo2' => '89888',
'foo1' => '89888',
'foo5' => '98980',
'foo3' => '89888',
'foo4' => '98980'
};

Answer 4

Var='foo2'
sed "#n
/${Var}/,/#[0-9]\{1,\}/ {
H
/#[0-9]\{1,\}/ !d
s/.*//;x
s/.//;s/\n.*\\n/ /p
q
}" YourFile
Not clear as request. It take first occurence of your pattern foo2 until first #number, remove line between and print both line in 1 than quit (no other extract

Answer 5

A Tcl solution. The procedure runs in a little over 3 microseconds, so you'll need very large data files to have it run for days. If more than one token matches, the first match is used (it's easy to rewrite the procedure to return all matches).
set data {
0foo1
0foo2
0foo3
\#89888
0foo4
0foo5
\#98980
0foo6
}
proc find {data pattern} {
set idx [lsearch -regexp $data $pattern]
if {$idx >= 0} {
lrange $data $idx $idx+1
}
}
find $data 0foo3
# -> 0foo3 #89888
find $data 0f.*5
# -> 0foo5 #98980
Documentation: if, lrange, lsearch, proc, set

Answer 6

sed
sed -n '/foo2/,/#[0-9]\+/ {s/^[[:space:]]*[0\\]//; p}' file |
sed -n '1p; $p' |
paste -s
The first sed prints all the lines between the first pattern and the 2nd, removing optional leading whitespace and the leading 0 or \.
The second sed extracts only the first and last lines.
The paste command prints the 2 lines as a single line, separated with a tab.
awk
awk -v p1=foo5 '
$0 ~ p1 {found = 1}
found && /#[0-9]+/ { sub(/^\\\/, ""); print p1, $0; exit }
' file
tcl
lassign $argv filename pattern1
set found false
set fid [open $filename r]
while {[gets $fid line] != -1} {
if {[string match "*$pattern1*" $line]} {
set found true
}
if {$found && [regexp {#\d+} $line number]} {
puts "$pattern1 $number"
break
}
}
close $fid
Then
$ tclsh 2patt.tcl file foo4
foo4 #98980

Answer 7

Is this what you want?
$ awk -v tgt="foo2" 'index($0,tgt){f=1} f&&/#[0-9]/{print tgt, $0; exit}' file
foo2 \#89888
$ awk -v tgt="foo5" 'index($0,tgt){f=1} f&&/#[0-9]/{print tgt, $0; exit}' file
foo5 \#98980
I'm using index() above as it searches for a string not a regexp and so could not care less what RE metacharacters are in foo - they are all just literal characters in a string.
It's not clear from your question if you want to find a specific number after a specific foo or the first number after foo2 or even if you want to search for a specific foo value or all "foo"s or...