[SOLVED] Setting 2 files for grep search in 1 unique variable

pedropt · 07-05-2023, 06:47 PM

Hi everyone , i am stuck here with a doubt , i want to set 2 files for grep search but i want to use them as an unique variable of both .

What i need :

Quote:

log1="/var/log/nginx/access.log"
log2="/var/log/nginx/access.log.1"
weblog="$log1" "$log2"

some command in grep next :
grep "something" "$weblog"

I get an error of file missing , but file is there .
I know that i can use them like this and it works :

Quote:

grep "something" "$log1" "$log2"

however if i set those 2 logs in 1 single variable i get an error .

I was thinking in setting just 1 log variable as :

log="/var/log/nginx/access.log*"

but this will include also the gzip files inside nginx logs directory , witch are access.log.2.gz , etc... , and i do not want that .

Any ideas how can i manage to set those 2 logs in one unique variable ?

Thank you

scasey · 07-05-2023, 07:53 PM

It would be helpful to see the error you got.

Code:

 weblog="$log1" "$log2"

returns “no such file…” for log.1 ($log2) because that statement tries to run it after putting $log1 into weblog. I think what you want is

Code:

weblog="$log1 $log2"

astrogeek · 07-05-2023, 08:33 PM

What scasey says is right - it is trying to execute log2. Put both inside the quotes.

Additionally, you must not quote $weblog in the grep statement or it will treat the entire string as one filename, "log1 log2". Your grep must be something like this:

Code:

log1="/var/log/nginx/access.log"
log2="/var/log/nginx/access.log.1"
weblog="$log1 $log2"
...
grep "something" $weblog

... which grep will see as two separate filename arguments.

michaelk · 07-05-2023, 08:48 PM

Quote:

grep "something" /var/log/nginx/access.log{,.1}

If you use brace expansion you do not need extra variables and grep will only search access.log and access.log.1

pedropt · 07-05-2023, 09:46 PM

Thank you for the replies on this subject .

using this variable :

weblog="$log1 $log2"

i get :

Quote:

grep: /var/log/nginx/access.log /var/log/nginx/access.log.1: No such file or dir ectory

I think grep is considering the 2 variables inside weblog an unique file instead of 2 , not sure .

Using :
weblog="$log1 $log2"

i get :
grep: : No such file or directory

And using mikaelk idea of :

log1="/var/log/nginx/access.log{,.1}"

does not work either because this script first checks if those files exists before launching the grep statement .

what i mean in mikael statement to not work is this :

Code:

log1="/var/log/nginx/access.log{,.1}"
if [[ ! -f "$log1" ]]
then
echo "Nginx log does not exist"
exit 0
fi
grep "something" "$log1"

NevemTeve · 07-05-2023, 11:23 PM

In some shells (eg bash) you can use arrays:

Code:

weblog=(file1 "file 2")
grep -- "something" "${weblog[@]}"

astrogeek · 07-05-2023, 11:38 PM

Quote:

Originally Posted by pedropt

using this variable :

weblog="$log1 $log2"

i get :

Code:

grep: /var/log/nginx/access.log /var/log/nginx/access.log.1: No such file or dir ectory

I think grep is considering the 2 variables inside weblog an unique file instead of 2 , not sure .

It would be helpful if you showed us the exact grep command you used. Did you quote $weblog in the grep command?

It should work if unquoted as noted above.

pedropt · 07-06-2023, 03:37 AM

Astrogeek

Quote:

It would be helpful if you showed us the exact grep command you used. Did you quote $weblog in the grep command?

yes i used .

the weblog variable in grep command also double quoted again like :

Quote:

log1="/var/log/nginx/access.log"
log2="/var/log/nginx/access.log.1"
weblog="$log1" "$log2"

grep "Something" "$weblog"

However i did not yet test it without double quotes in grep , going to do it now to check output .

pedropt · 07-06-2023, 03:44 AM

Hello again guys , Thank you for the perspective you gave in your last comment astrogeek .
I found the solution .

To work it must be like this :

Quote:

log1="/var/log/nginx/access.log"
log2="/var/log/nginx/access.log.1"
weblog="$log1 $log2"

grep "Something" $weblog

I just have test it now .

NevemTeve · 07-06-2023, 04:11 AM

Be careful not to have spaces in your filenames.

pedropt · 07-06-2023, 04:23 AM

Quote:

Be careful not to have spaces in your filenames.

yes , i know , or grep will consider for every space a single file .

MadeInGermany · 07-06-2023, 04:59 AM

The standard shell has only your unsafe solution.
bash/ksh/zsh have arrays for a safe solution:

Code:

log1="/var/log/nginx/access.log"
log2="/var/log/nginx/access.log.1"
logs=( "$log1" "$log2" )

grep "Something" "${logs[@]}"

It is important to have @ (not *), then the quotes allow splitting into array members but protect the members against expansions (word splitting and filename generation).

pedropt · 07-06-2023, 05:19 AM

i could do it differently , since i am parsing the log files for anomalies i could create 1 unique temporary file with the content of access.log and access.log.1 and parse that temporary file instead going directly to nginx live logs .

This is what i mean .

Code:

log1="/var/log/nginx/access.log"
log2="/var/log/nginx/access.log.1"
weblog="/tmp/temp.log"
cat "$log1" "$log2" > /tmp/temp.log
grep "something" "$weblog"

However for now i do not think it is necessary for my needs here .

NevemTeve · 07-06-2023, 05:25 AM

Quote:

Originally Posted by pedropt

... grep will consider for every space a single file .

Not `grep`, the shell.

In your second sample, you could spare the temporal file:

Code:

(set "/var/log/nginx/access.log" "/var/log/nginx/access.log.1"
grep -h "something" "$@")

pedropt · 07-06-2023, 06:51 AM

Quote:

Originally Posted by NevemTeve

Not `grep`, the shell.

In your second sample, you could spare the temporal file:

Code:

(set "/var/log/nginx/access.log" "/var/log/nginx/access.log.1"
grep -h "something" "$@")

better than that would be setting a variable with all that content , like :

Quote:

weblog=$(cat "$log1" "$log2")

This way i could use it everywhere in script ahead , i only had to change the way grep parses the var like :

Quote:

echo "$weblog" | grep "something"

But i do not need it , we are just speaking about possible alternatives available for the same output .