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grep with regular expression

Posted on 2012-04-11
Medium Priority
Last Modified: 2012-04-12
mysql -S /tmp/mysql.sock -e ' SHOW GLOBAL STATUS  ' | grep 'Com_insert'
 which gives bellow result

Com_insert      353
Com_insert_select       0

but this

/opt/mysql/server-5.5/bin/mysql -S /tmp/mysql.sock -e ' SHOW GLOBAL STATUS  ' |  grep 'Com_insert' | grep -v 'Com_insert_select'

it gives
Com_insert      353
which is right..
but is there any clean way to write this command  so that
i only get 'Com_insert      353'

i meant : by using regular expression or regular expresson + awk   ??
Question by:fosiul01
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LVL 84

Accepted Solution

ozo earned 1000 total points
ID: 37832391
A pure regular expression equivalent to  grep 'Com_insert' | grep -v 'Com_insert_select'  can get a little awkward to write.
It may be easier to use something like
perl -ne 'print if /Com_insert(?!_select)/'
LVL 23

Assisted Solution

by:Maciej S
Maciej S earned 1000 total points
ID: 37832419
use -w option for grep:

/opt/mysql/server-5.5/bin/mysql -S /tmp/mysql.sock -e ' SHOW GLOBAL STATUS  ' |  grep -w 'Com_insert'
LVL 84

Expert Comment

ID: 37832439
As a single egrep expression, it would be
egrep 'Com_insert($|[^_]|_($|[^s])|_s($|[^e])|_se($|[^l])|_sel($|[^e])|_sele($|[^c])|_selec($|[^t]))'
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LVL 84

Expert Comment

ID: 37832459
grep -w 'Com_insert'
is not equivalent to grep 'Com_insert' | grep -v 'Com_insert_select'
because grep 'Com_insert' | grep -v 'Com_insert_select' would match something like "Com_insertion"
whereas grep -w 'Com_insert' would not
LVL 23

Expert Comment

by:Maciej S
ID: 37832489
I agree - it's not equivalent, but it's an answer for fosiul's question (with his output).
LVL 84

Expert Comment

ID: 37832541
for the specific output listed in the question,
grep 'Com_insert' | awk 'NR==1'
would also be an answer,
so would
grep 'Com_insert     353'
LVL 23

Expert Comment

by:Maciej S
ID: 37832665
I won't argue with this - your perl solution is the most general one - I agree.
But - for this specific question, where input for grep is "show global status" output - my version is simpler, and will not cause unwanted output. And yes - author can also run "grep 'Com_insert '" (with space at the end). IMO -w option is better than adding space. It's (still IMO) also better then your perl - it's simpler and shorter. If author wants to use it in future in some other cases, than your perl may be better (it depends on input for grep/perl).

One more solution - without any grep, awk, perl, etc:

/opt/mysql/server-5.5/bin/mysql -S /tmp/mysql.sock -e ' SHOW GLOBAL STATUS  where variable_name="Com_insert"'
LVL 23

Expert Comment

by:Maciej S
ID: 37832672
Above will output headers also. The one with desired output only (with -B -N options for mysql):

/opt/mysql/server-5.5/bin/mysql -S /tmp/mysql.sock -e ' SHOW GLOBAL STATUS  where variable_name="Com_insert"' -BN
LVL 29

Author Comment

ID: 37833002
Hi thanks for variataion ...

just one more variation i want to add , this also gives the accurate result ..

/opt/mysql/server-5.5/bin/mysql -S /tmp/mysql.sock -e ' SHOW GLOBAL STATUS  ' | awk '$1~/^Com_insert$/ {print $2}'

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