Lab 5.1 - question concerning Linux 'cut' command
Hi- This is not a show stopper, but I have done considerable research to understand this command. Just looking to understand this.
1. export client=$(grep client-cert $HOME/.kube/config |cut -d" " -f 6)
From what I have researched I understand the -d flag to indicate a delimiter of a blank space following the text 'client-cert' from where to begin the cut operation; however when looking into the -f flag, all I could find were examples using .csv files. If -f is for 'field', I am not quite sure what field 6 indicates. I understood examples that referenced .csv files, but kind of lost here. Any explanation to this would be greatly appreciated.
Comments
-
Hi @jcremp77,
Ideally, this kind of question would be posted and answered in a Linux course related forum
Assuming your content is
field1,field2,field3
, runningcut -d "," -f 2
yields "field2".
Assuming your content isfield1 field2 field3
, runningcut -d " " -f 2
yields "field2" as well.What do you think happens, if your delimiter is one blank space (just like the second example above
-d " "
) and your fields were not equally delimited by single spaces, such asfield1 field2 field3
(there should be 5 blank spaces between the first two fields and 1 single blank space between the last two fields). Try running the same commandcut -d " " -f 2
and see if the output makes sense. Change the value of-f
until you see a significant change in the output. Can you explain what caused the change? Was the change expected at all?EDIT: For some reason the 5 blank spaces are compressed into 1 single space, but try it either way by typing out the fields and leave 5 spaces between the first two.
Regards,
-Chris0 -
Hi @chrispokorni ,
I am not sure I can articulate it well but I understand why the following is expected (text separated by 5 spaces)
Note: used for the same reason you mentioned in your replyfield1<5spc>field2<5spc>field3
, running cut -d " " -f 2 results in "blank"field1<5spc>field2<5spc>field3
, running cut -d " " -f 6 results in "field2"field1<5spc>field2<5spc>field3
, running cut -d " " -f 11 results in "field3"
For a single file with 3 rows (1st row separated by 1 space, 2nd by 2, and 3rd by 3)
#start of file
field1<1spc>field2<1spc>field3
field1<2spc>field2<2spc>field3
field1<3spc>field2<3spc>field3
#end of fileIf running 'cut -d " " -f 3' on the file above the result would be:
field3
field2
<blank>
In the above '-f 3' indicates that what follows the 2nd " " will be output for every line in the file; hence the 3rd line returning nothing because 'field1' and 'field2' are separated by 3 " "'s; but '-f 4' would return:
<blank>
<blank>
field2
Thank you for taking the time to give an explanation to the following command:
export client=$(grep client-cert $HOME/.kube/config |cut -d" " -f 6)
Now if the above command had the value of "-f" were changed to 5, then the following output would be:
client-certificate-data:
0
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