[SOLVED] Synchronization of date between server and apache webserver, grep and sed instructions.

michaelk · 11-28-2018, 05:17 AM

If your server was not showing the correct date then something could be wrong with your server or its internet connection or how ntp is configured.

Code:

while read var value
do
"$var"= curl -XPUT 'http://google.com-'$date'
done

You have many syntax errors with your loop. And while we could fix the errors if the server and ntp is configured and running correctly you should not have a date problem.

berndbausch · 11-28-2018, 05:43 AM

If NTP is working correctly, you get the best possible date from the internet already.

But if you want it from a URL, here is a solution:

Code:

curl -i https://google.com 2>/dev/null | grep Date | sed ‘s/Date: //‘
Wed, 28 Nov 2018 11:36:09 GMT

The grep command selects the line that contains the Date header. The sed command removes the string “Date: “.

pan64 · 11-28-2018, 08:03 AM

Off topic, but do not use grep|sed chains (or similar) if not really needed:

Code:

curl -i https://google.com 2>/dev/null | grep -o -P '(?<=Date: ).* ...'
curl -i https://google.com 2>/dev/null | sed -n '/Date/{s/Date: //;p}'

l0f4r0 · 11-28-2018, 08:25 AM

@1s440: can you please change your thread title (currently: "Script") into something much more specific? (HOWTO: select a new title by editing your thread original post)

1s440 · 11-28-2018, 08:33 AM

Quote:

Originally Posted by berndbausch

If NTP is working correctly, you get the best possible date from the internet already.

But if you want it from a URL, here is a solution:

Code:

curl -i https://google.com 2>/dev/null | grep Date | sed ‘s/Date: //‘
Wed, 28 Nov 2018 11:36:09 GMT

The grep command selects the line that contains the Date header. The sed command removes the string “Date: “.

Hi Thanks for the reply. This work as ntp is configured correctly.

1s440 · 11-28-2018, 08:38 AM

Quote:

Originally Posted by l0f4r0

@1s440: can you please change your thread title (currently: "Script") into something much more specific? (HOWTO: select a new title by editing your thread original post)

hi Unable to change the thread title. sorry

l0f4r0 · 11-28-2018, 08:39 AM

Quote:

Originally Posted by 1s440

Hi Thanks for the reply. This work as ntp is configured correctly. Then don't need a script.

Then please mark your thread as [SOLVED]

Quote:

Originally Posted by 1s440

hi Unable to change the thread title. sorry

What doesn't work with the HOWTO I provided to you?

berndbausch · 11-28-2018, 09:07 AM

Quote:

Originally Posted by pan64

Off topic, but do not use grep|sed chains (or similar) if not really needed:

Code:

curl -i https://google.com 2>/dev/null | grep -o -P '(?<=Date: ).* ...'
curl -i https://google.com 2>/dev/null | sed -n '/Date/{s/Date: //;p}'

This is very useful, but the curly braces in the sed command are a bit too baroque for my taste. What’s wrong with

Code:

sed -n ‘/^Date/s/Date: //p’

?

And I refuse to learn Perl.

l0f4r0 · 11-28-2018, 09:19 AM

Quote:

Originally Posted by berndbausch

This is very useful, but the curly braces in the sed command are a bit too baroque for my taste. What’s wrong with

Code:

sed -n ‘/^Date/s/Date: //p’

?

I didn't know about the p flag in substitution command, thank you!
Actually, this doesn't change anything in this simple example. So well done

But braces are still required for more advanced use-cases when you need to nest instructions in relation to a /pattern/...

1s440 · 11-28-2018, 09:19 AM

Quote:

Originally Posted by berndbausch

This is very useful, but the curly braces in the sed command are a bit too baroque for my taste. What’s wrong with

Code:

sed -n ‘/^Date/s/Date: //p’

?

And I refuse to learn Perl.

Code:

#!/bin/bash
date
VAR=$(curl -i http://google.com/ | grep Date)
echo "Today date is "$date""
echo "Output is "$VAR""
if [ $VAR -eq $date ]; then
echo "date is correct"
else
echo "date is wrong"
fi

l0f4r0 · 11-28-2018, 09:34 AM

Quote:

Originally Posted by 1s440

#!/bin/bash
date
VAR=$(curl -i http://google.com/ | grep Date)
echo "Today date is "$date""
echo "Output is "$VAR""
if [ $VAR -eq $date ]; then
echo "date is correct"
else
echo "date is wrong"
fi

-eq is a numerical comparison so you need surrounding double parentheses ((. But I don't think it's gonna work because date returns a string... So you may want [[ $VAR == $date ]] instead (if I were you I would prefer using double square brackets ([[) instead of single bracket command ([) in your bash scripts).
Where is your date variable initialized?
What makes you think it answers berndbausch's question?

And finally, please use [CODE] tags.

michaelk · 11-28-2018, 09:41 AM

A direct comparison of the two variables will never be the same.

The header is in UTC(GMT) so you need to use the date -u command. In addition time will never match and the format is different. Are you trying to verify the day, time or both?

1s440 · 11-28-2018, 09:46 AM

Quote:

Originally Posted by 1s440

Hi Thanks for the reply. This work as ntp is configured correctly.

Unfortunately sed is not working little complicated

1s440 · 11-28-2018, 09:48 AM

Quote:

Originally Posted by l0f4r0

If you are writing a bash script, then if I were you I would prefer using double square brackets ([[) instead of single bracket command ([).
Where is date variable initialized?
What makes you think it answers berndbausch's question?

And finally, please use [CODE] tags.

Hi Ignore the previous here is the correct but facing problems with sed

Code:

#!/bin/bash
date
VAR=$(curl -i http://google.com/ | grep Date | sed ‘s/Date: //‘ )
echo "´Today date is $(date)´"
echo "Output is $VAR"
if [[ $VAR -eq $(date) ]]; then
echo "´correct´"
else
echo "´wrong´"
fi

")syntax error in expression (error token is ": Wed, 28 Nov 2018 15:35:29 GMT
´wrong´

l0f4r0 · 11-28-2018, 09:58 AM

Quote:

Originally Posted by 1s440

Hi Ignore the previous here is the correct but facing problems with sed

#!/bin/bash
date
VAR=$(curl -i http://google.com/ | grep Date | sed ‘s/Date: //‘ )
echo "´Today date is $(date)´"
echo "Output is $VAR"
if [[ $VAR -eq $(date) ]]; then
echo "´correct´"
else
echo "´wrong´"
fi

")syntax error in expression (error token is ": Wed, 28 Nov 2018 15:35:29 GMT
´wrong´

Please see my previous (edited) post (your problem is not sed related but it's about -eq instruction inside double brackets).