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
Categories
- All Categories
- 50 LFX Mentorship
- 103 LFX Mentorship: Linux Kernel
- 575 Linux Foundation IT Professional Programs
- 304 Cloud Engineer IT Professional Program
- 125 Advanced Cloud Engineer IT Professional Program
- 53 DevOps Engineer IT Professional Program
- 60 Cloud Native Developer IT Professional Program
- 5 Express Training Courses
- 5 Express Courses - Discussion Forum
- 2K Training Courses
- 19 LFC110 Class Forum
- 7 LFC131 Class Forum
- 27 LFD102 Class Forum
- 157 LFD103 Class Forum
- 20 LFD121 Class Forum
- 1 LFD137 Class Forum
- 61 LFD201 Class Forum
- 1 LFD210 Class Forum
- LFD210-CN Class Forum
- 1 LFD213 Class Forum - Discontinued
- 128 LFD232 Class Forum
- LFD237 Class Forum
- 23 LFD254 Class Forum
- 611 LFD259 Class Forum
- 105 LFD272 Class Forum
- 1 LFD272-JP クラス フォーラム
- 1 LFD273 Class Forum
- 2 LFS145 Class Forum
- 24 LFS200 Class Forum
- 739 LFS201 Class Forum
- 1 LFS201-JP クラス フォーラム
- 11 LFS203 Class Forum
- 75 LFS207 Class Forum
- 300 LFS211 Class Forum
- 54 LFS216 Class Forum
- 47 LFS241 Class Forum
- 41 LFS242 Class Forum
- 37 LFS243 Class Forum
- 11 LFS244 Class Forum
- 36 LFS250 Class Forum
- 1 LFS250-JP クラス フォーラム
- LFS251 Class Forum
- 140 LFS253 Class Forum
- LFS254 Class Forum
- 1.1K LFS258 Class Forum
- 10 LFS258-JP クラス フォーラム
- 93 LFS260 Class Forum
- 132 LFS261 Class Forum
- 33 LFS262 Class Forum
- 80 LFS263 Class Forum
- 15 LFS264 Class Forum
- 11 LFS266 Class Forum
- 18 LFS267 Class Forum
- 17 LFS268 Class Forum
- 23 LFS269 Class Forum
- 203 LFS272 Class Forum
- 1 LFS272-JP クラス フォーラム
- LFS274 Class Forum
- LFS281 Class Forum
- 234 LFW211 Class Forum
- 172 LFW212 Class Forum
- 7 SKF100 Class Forum
- SKF200 Class Forum
- 902 Hardware
- 219 Drivers
- 74 I/O Devices
- 44 Monitors
- 115 Multimedia
- 209 Networking
- 101 Printers & Scanners
- 85 Storage
- 763 Linux Distributions
- 88 Debian
- 66 Fedora
- 15 Linux Mint
- 13 Mageia
- 24 openSUSE
- 142 Red Hat Enterprise
- 33 Slackware
- 13 SUSE Enterprise
- 357 Ubuntu
- 479 Linux System Administration
- 41 Cloud Computing
- 70 Command Line/Scripting
- Github systems admin projects
- 95 Linux Security
- 78 Network Management
- 108 System Management
- 49 Web Management
- 68 Mobile Computing
- 23 Android
- 30 Development
- 1.2K New to Linux
- 1.1K Getting Started with Linux
- 537 Off Topic
- 131 Introductions
- 217 Small Talk
- 21 Study Material
- 826 Programming and Development
- 278 Kernel Development
- 514 Software Development
- 928 Software
- 260 Applications
- 184 Command Line
- 3 Compiling/Installing
- 76 Games
- 316 Installation
- 62 All In Program
- 62 All In Forum
Upcoming Training
-
August 20, 2018
Kubernetes Administration (LFS458)
-
August 20, 2018
Linux System Administration (LFS301)
-
August 27, 2018
Open Source Virtualization (LFS462)
-
August 27, 2018
Linux Kernel Debugging and Security (LFD440)