CODEWITHSUNDEEP
regexlinuxbashsed
Sandeepan Nath
Sandeepan Nath

Reputation: 10284

Unable to parse bash output using regex and collect a part of it

I am trying to parse out the recent load, from the output of this command - 

[sandeepan@ip-10-169-92-150 ~]$ w
 14:22:21 up 17 days, 51 min,  2 users,  load average: 0.00, 0.01, 0.05
USER     TTY      FROM              LOGIN@   IDLE   JCPU   PCPU WHAT
sandeepa pts/0    115.112.95.170   06:38   43:57   0.51s  0.51s -bash
sandeepa pts/1    115.112.95.170   13:17    4.00s  0.03s  0.00s w

The first one after the load average: -

                |
               \|/
load average: 0.00, 0.01, 0.05

I was using this, which worked - 

w | awk '{print $10}' | tr -d ,

However, I realised that the value I am looking for may not always be the 10th variable. Hence I am trying to use regex here, but unfortunately, not able to use it with any of the few bash commands/utilities I know.

I have this regular expression, with which I am able to match the desired value -

/.*load average:\s([0-9]+\.[0-9]+),.*/m

I tried looking at the sed manual, looking at some other questions like Using sed to remove unwanted characters from output, but could not understand much to make mine working.

Upvotes: 1

Views: 54

Answers (1)

fedorqui
fedorqui

Reputation: 289735

When you know what text comes before and after, it is best to use a look-behind that does this: checks the text in a given place, no matter what is the rest of the line.

Given your sample file, I stored it in a file and did this:

$ grep -Po '(?<=load average: )[^,]*' file
0.00

This is saying: hey, get all the text after load average: and until a comma is found.

So if you have a file like this:

$ cat file
14:22:21 up 17 days, 51 min,  2 users,  load average: 0.00, 0.01, 0.05
hello how are you,  load average: 1.23, 0.01, 0.05

It will return as follows:

$ grep -Po '(?<=load average: )[^,]*' file
0.00
1.23

Note by the way that man w can give you good hints on how to get this info with some options, as well as man top.

Upvotes: 1

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