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How do we display specific row of an output from bottom given line number?


 
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Top Forums Shell Programming and Scripting How do we display specific row of an output from bottom given line number?
# 1  
Old 02-12-2020
How do we display specific row of an output from bottom given line number?

I pass a number to my script. Passing "1" below.

Code:
./getfile.sh 1
echo "User entered: $1"
 ls -ltr *.conf | sed -n '$p'

I wish to use ls -ltr i.e list files in ascending order of time the latest showing at the bottom of the output.

Number 1 should get me the last row of ls -ltr output i.e the latest file.
Passing Number "2" should get me the second last row of the output.
Number "3 would get me the 3rd last row and so forth.

I wish to use only sed for this purpose as it is works smoothy across different flavors of Operating Systems that I have.

ls -ltr | sed -n '$p' gives me the last row whereas ls -ltr | sed -n 3p gives me the third row from top.

I'm not sure how can I give an equation so that based on user input, I could get my sed to display corresponding row of output.
# 2  
Old 02-12-2020
You want the 3rd (...) newest file? Try NOT reversing the sorting order
Code:
ls -lt *.conf | sed -n "${1}p"

This User Gave Thanks to RudiC For This Post:
# 3  
Old 02-12-2020
If the user passes 1 then i need the newest latest file.

If the user passes 2 then i wish to display only the newest - 1 file i.e second latest file.

if the user passes 3 then the third latest file.

Code:
-bash-4.2$ ls -lt *.conf*
-rwxrwxrwx 1 user1 user 21627 Feb 11 17:17 httpd.conf_1581421731
-rwxrwxrwx 1 user1 user 15445 Feb 11 17:14 httpd-ssl.conf_1581421731
-rwxrwxrwx 1 user1 user 21624 Feb 11 17:13 httpd.conf_1581421456
-rwxrwxrwx 1 user1 user 15445 Feb 11 15:39 httpd-ssl.conf_1581421372
-rwxrwxrwx 1 user1 user 15445 Feb 11 15:39 httpd-ssl.conf_1581421456
-rwxrwxrwx 1 user1 user 21627 Feb 11 13:35 httpd.conf_1581408391
-rwxrwxrwx 1 user1 user 21627 Feb 11 13:35 httpd.conf_1581413246
-rwxrwxrwx 1 user1 user 21627 Feb 11 13:35 httpd.conf_1581415778
-rwxrwxrwx 1 user1 user 21627 Feb 11 13:35 httpd.conf_1581421372
-rwxrwxrwx 1 user1 user 21644 Feb 11 13:29 httpd.conf_1581408244
-rwxrwxrwx 1 user1 user 21644 Feb 11 13:29 httpd.conf_1581408293
-rwxrwxrwx 1 user1 user 21627 Feb 11 11:13 httpd.conf_1581399897
-rwxrwxrwx 1 user1 user 21627 Feb 11 11:13 httpd.conf_1581407966
-rwxrwxrwx 1 user1 user 15445 Feb 11 11:12 httpd-ssl.conf_1581399897
-rwxrwxrwx 1 user1 user 15445 Feb 11 11:12 httpd-ssl.conf_1581407966
-rwxrwxrwx 1 user1 user 15445 Feb 11 11:12 httpd-ssl.conf_1581408244
-rwxrwxrwx 1 user1 user 15445 Feb 11 11:12 httpd-ssl.conf_1581408293
-rwxrwxrwx 1 user1 user 15445 Feb 11 11:12 httpd-ssl.conf_1581408391
-rwxrwxrwx 1 user1 user 15445 Feb 11 11:12 httpd-ssl.conf_1581413246
-rwxrwxrwx 1 user1 user 15445 Feb 11 11:12 httpd-ssl.conf_1581415778
-bash-4.2$ ls -lt | sed -n "${1}p"
total 400
-rwxrwxrwx 1 user1 user 21627 Feb 11 17:17 httpd.conf_1581421731
-rwxrwxrwx 1 user1 user 15445 Feb 11 17:14 httpd-ssl.conf_1581421731
-rwxrwxrwx 1 user1 user 21624 Feb 11 17:13 httpd.conf_1581421456
-rwxrwxrwx 1 user1 user 15445 Feb 11 15:39 httpd-ssl.conf_1581421372
-rwxrwxrwx 1 user1 user 15445 Feb 11 15:39 httpd-ssl.conf_1581421456
-rwxrwxrwx 1 user1 user 21627 Feb 11 13:35 httpd.conf_1581408391
-rwxrwxrwx 1 user1 user 21627 Feb 11 13:35 httpd.conf_1581413246
-rwxrwxrwx 1 user1 user 21627 Feb 11 13:35 httpd.conf_1581415778
-rwxrwxrwx 1 user1 user 21627 Feb 11 13:35 httpd.conf_1581421372
-rwxrwxrwx 1 user1 user 21644 Feb 11 13:29 httpd.conf_1581408244
-rwxrwxrwx 1 user1 user 21644 Feb 11 13:29 httpd.conf_1581408293
-rwxrwxrwx 1 user1 user 21627 Feb 11 11:13 httpd.conf_1581399897
-rwxrwxrwx 1 user1 user 21627 Feb 11 11:13 httpd.conf_1581407966
-rwxrwxrwx 1 user1 user 15445 Feb 11 11:12 httpd-ssl.conf_1581399897
-rwxrwxrwx 1 user1 user 15445 Feb 11 11:12 httpd-ssl.conf_1581407966
-rwxrwxrwx 1 user1 user 15445 Feb 11 11:12 httpd-ssl.conf_1581408244
-rwxrwxrwx 1 user1 user 15445 Feb 11 11:12 httpd-ssl.conf_1581408293
-rwxrwxrwx 1 user1 user 15445 Feb 11 11:12 httpd-ssl.conf_1581408391
-rwxrwxrwx 1 user1 user 15445 Feb 11 11:12 httpd-ssl.conf_1581413246
-rwxrwxrwx 1 user1 user 15445 Feb 11 11:12 httpd-ssl.conf_1581415778


Thus if the user passes 3 then the below file should be be printed
Code:
-rwxrwxrwx 1 user1 user 15445 Feb 11 11:12 httpd-ssl.conf_1581408391

if the user passes 4 then the below file should be be printed
Code:
-rwxrwxrwx 1 user1 user 15445 Feb 11 11:12 httpd-ssl.conf_1581408293

@Rudic your suggestion does not help get my desired output. Kindly suggest.
# 4  
Old 02-12-2020
How can

Code:
-rwxrwxrwx 1 user1 user 15445 Feb 11 11:12 httpd-ssl.conf_1581408293

be the 4th newest file if
Code:
-rwxrwxrwx 1 user1 user 21627 Feb 11 17:17 httpd.conf_1581421731
-rwxrwxrwx 1 user1 user 15445 Feb 11 17:14 httpd-ssl.conf_1581421731
-rwxrwxrwx 1 user1 user 21624 Feb 11 17:13 httpd.conf_1581421456
-rwxrwxrwx 1 user1 user 15445 Feb 11 15:39 httpd-ssl.conf_1581421372

exist?
# 5  
Old 02-12-2020
OK what have you done so far?

As we agree the first code you gave in #1 wont take you very far...

Passing numbers, OK but what if its not the case? like char or words, what happens?

Writing a script that accepts arguments is something nice, but unless its for your own usage, it should be fool proof and properly written Like :

No argument -> display usage

Testing the argument values etc...

Last edited by Neo; 02-12-2020 at 12:58 PM..
# 6  
Old 02-12-2020
Quote:
Originally Posted by RudiC
How can

Code:
-rwxrwxrwx 1 user1 user 15445 Feb 11 11:12 httpd-ssl.conf_1581408293

be the 4th newest file if
Code:
-rwxrwxrwx 1 user1 user 21627 Feb 11 17:17 httpd.conf_1581421731
-rwxrwxrwx 1 user1 user 15445 Feb 11 17:14 httpd-ssl.conf_1581421731
-rwxrwxrwx 1 user1 user 21624 Feb 11 17:13 httpd.conf_1581421456
-rwxrwxrwx 1 user1 user 15445 Feb 11 15:39 httpd-ssl.conf_1581421372

exist?
@Rudic sorry that was by overlook. With parameter 3 the row returned should be the third row ie.
Code:
-rwxrwxrwx 1 user1 user 21624 Feb 11 17:13 httpd.conf_1581421456

Likewise when the user passes 4 the 4th latest row should be returned i.e
Code:
-rwxrwxrwx 1 user1 user 15445 Feb 11 15:39 httpd-ssl.conf_1581421372

But, as I shared the output of your suggestion i get a list of rows and not that single particular row corresponding to the argument passed to the script.

@vbe thank you for the points you highlighted however, the parameter is checked by a Jenkins UI tool and my script will only be executed once a number is passed to that script by the user. Thus the argument to my script is certainly an integer.

Kindly suggest
# 7  
Old 02-12-2020
We have not seen any code so far and waiting to see this famous script...
Quote:
the parameter is checked by a Jenkins UI tool and my script will only be executed once a number is passed to that script by the user.
Oh thats interesting, where is the code?

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