Shell Programming and Scripting

# wc -l <infile
   83678

# grep -n 'Start' infile
1001:Start

# time tail infile | sed -n '/Start/{=;q;}'

real    0m0.072s
user    0m0.019s
sys     0m0.046s

# time sed -n '/Start/{=;q;}' infile
1001

real    0m0.037s
user    0m0.010s
sys     0m0.022s

 
$> vStart='Started'; awk -vn=$vStart '$0~n{p=NF+1} END{print p}' abc.log
awk: syntax error near line 1
awk: bailing out near line 1
 
$> vStart='Started';nawk -vn=$vStart '$0~n{print NR;exit}' abc.log
nawk: empty regular expression
 input record number 1, file abc.log
 source line number 1

 
$> tail -r abc.log | sed -n '/Started/{=;q;}' 
2

 
sed -n '1!G;h;$p'

 
$> sed -n -e '1!G;h;$p; /Started/{=;q}' abc.log
sed: command garbled: 1!G;h;$p; /Started/{=;q}

# sed -n '/Start/{=;q;}' infile
1001

# tail infile|sed -n '/Start/{p;q;}'

I actually mentioned about that "q" command with sed so it can take only a single-line address and 
when once the line matching address reached, the sed will be terminated,therefore, 
just sed with q must spend less effort than tail reads and use pipe(s)..

# sed -n '1!G;h;$p'

# sed '1!G;h;$p' infile | sed -n '/121/{=;q;}'