[SOLVED] #!bin/sh script mysql command won't redirect to /dev/null

RagingRaven · 10-26-2016, 06:51 AM

Quote:

Originally Posted by keefaz

You can put the command in a subshell like

Code:

( command -args "bla" & )

Ok, but do I still need to redirect to /dev/null or not?

So in other words would my line become?:

Code:

( mysql -u${mysqlUser} -p${mysqlPass} -Ae"FLUSH TABLES WITH READ LOCK; SELECT SLEEP(86400)" & )

or?:

Code:

( mysql -u${mysqlUser} -p${mysqlPass} -Ae"FLUSH TABLES WITH READ LOCK; SELECT SLEEP(86400)" & ) > /dev/null 2>&1

Thanks

RagingRaven · 10-26-2016, 06:56 AM

Thank you keefaz!

using

Code:

( mysql -u${mysqlUser} -p${mysqlPass} -Ae"FLUSH TABLES WITH READ LOCK; SELECT SLEEP(86400)" & ) > /dev/null 2>&1

I'm finally rid of the output generated.

Turbocapitalist · 10-26-2016, 06:56 AM

The latter.

You'll want to look up a little bit about subshells, redirects, and background processes that you are using here. They will be useful in other situations. Some starting points:

http://mywiki.wooledge.org/SubShell
http://mywiki.wooledge.org/BashGuide...ut#Redirection
http://mywiki.wooledge.org/ProcessMa..._background.3F

There is other good reading material elsewhere, too.

RagingRaven · 10-26-2016, 07:08 AM

Quote:

Originally Posted by Turbocapitalist

The latter.

You'll want to look up a little bit about subshells, redirects, and background processes that you are using here. They will be useful in other situations. Some starting points:

http://mywiki.wooledge.org/SubShell
http://mywiki.wooledge.org/BashGuide...ut#Redirection
http://mywiki.wooledge.org/ProcessMa..._background.3F

There is other good reading material elsewhere, too.

Thanks Turbo, I'll take a look at it, I understand the basics, but this looks a little more in depth.

ondoho · 10-26-2016, 02:59 PM

Quote:

Originally Posted by RagingRaven

Code:

( mysql -u${mysqlUser} -p${mysqlPass} -Ae"FLUSH TABLES WITH READ  LOCK; SELECT SLEEP(86400)" & ) > /dev/null 2>&1

I'm finally rid of the output generated.

yes, but does the script do what it should?
i'm pretty sure that this:

Quote:

Originally Posted by RagingRaven

Just tried with set -e -x and it is indeed the last line that's outputting.
What I did see though was that the command shown was:

Code:

mysql -u<user> -p<pass> '-AeKILL QUERY <id>;'

Which seems different from what's in my code, not only missing the > /dev/null 2>&1 part, but also having single quotes and missing double quotes:

Code:

mysql -u${mysqlUser} -p${mysqlPass} -Ae"KILL QUERY ${SLEEP_ID};" > /dev/null 2>&1

means that there MUST be a space between -Ae and "KILL QUERY ${SLEEP_ID};", so it should read:

Code:

mysql -u${mysqlUser} -p${mysqlPass} -Ae "KILL QUERY ${SLEEP_ID};" > /dev/null 2>&1

try that again.

RagingRaven · 10-26-2016, 04:23 PM

@ondoho

Even though there is no space between -e and the query, it does appear to be working fine.

Code:

mysql -u${mysqlUser} -p${mysqlPass} -Ae"FLUSH TABLES WITH READ LOCK; SELECT SLEEP(86400)" &

works because I can see a query running when looking at the processlist.

Code:

mysql -u${mysqlUser} -p${mysqlPass} -Ae"KILL QUERY ${SLEEP_ID};"

also works, because after this command the correct query is no longer running.

So although I agree with you that it looks better to add a space, it doesn't appear necessary

The command itself was never the issue though, that was working fine, it was the output I couldn't get rid of.
Luckily, with a little help from keefaz, it's fixed now though.