LFCS: How to use GNU ‘sed’ Command to Create, Edit, and Manipulate files in Linux – Part 1

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Gabriel Cánepa

Gabriel Cánepa is a GNU/Linux sysadmin and web developer from Villa Mercedes, San Luis, Argentina. He works for a worldwide leading consumer product company and takes great pleasure in using FOSS tools to increase productivity in all areas of his daily work.

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Linux Foundation LFCS and LFCE Certification Preparation Guide

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42 Responses

  1. Rpn says:

    # last | grep gacanepa | tr -s ‘ ‘ | cut -d’ ‘ -f1,3 | sort -k2 | uniq

    While I was learning, I found out that `backticks` do not work as shown in the example, but single ticks do. I found this true on Ubuntu/Linux Mint so I guess also on Debian. Is this a “distro difference issue” or is the example just wrong? I mean, in the other examples with TR single ticks are used. Please make sure you correct this as these ticks or back quotes can confuse Linux beginners.

  2. Freddy Dominguez says:

    I am excited, and take the first lesson !!

    Here I come…!

  3. justin says:

    I passed the LFCS .

    I used LF material for my first test and found the LF study material to be lacking…

    I got a free retake so my first attempt was really to see what I was in for..

    2nd attempt, passed with help from this guide.

    thanks to the author.

  4. Matt says:

    >In the above command, a ^ (carrot sign) is a well-known regular expression that is used to represent the beginning of a line.

    It’s a “caret” not a carrot.

    My sides are in orbit!

  5. @lvin says:

    One more thing….
    du -sch /var/* | sort -h
    sort in Ubuntu doesn’t have -h parameter
    But CentOS has it.

    • @lvin,
      I just checked in 12.04 LTS and the -h option is there. Please note that sort, as installed by default on most distributions, is part of the GNU coreutils package. What does the output of ‘info sort’ return for you?

  6. @lvin says:

    I have a question.

    # sed -n ‘/^Jun 8/ p’ /var/log/messages | sed -n 1,5p

    I understand the first parameter s is for substitute.
    What is the meaning without any parameter?


    • @lvin,
      Please refer to the paragraphs immediately above and below the code line that you quoted. Sed, without s, is used to print to standard output, a portion of a file that begins with the pattern that is passed to it as argument.

  7. Ashish says:

    I passed LFCS exam. A big thanks to TECMINT team.

    LFCS is a fun because it’s hands on exam and we have access to man pages. LFCS syllabus is a big thumbs down as they don’t give out any specifics. I was often confused on how much to study or what exactly to study.

    These articles provided me a rough specifics of syllabus (what I needed to look into). They are a good starting point and also a quick revising place when I was done preparing.

    Just a heads up to all the aspiring candidates, these articles are not the everything we need to know of LFCS. I had referred many other video tutorials and websites as well.

    I would definitely recommend all to have 3 things at disposal : Any reference book (tldp.org) , a good video series (Professor Messer / CBT Nuggets/udemy ) and Techmint articles.

    Lastly and most importantly, all of you MUST have access to Linux machine to play around.

    To utilize these articles fully, I navigated to all the external links listed in the articles. Played around googling the complex things. Came back later when I was comfortable enough and resumed my study. Muscle memory is very important in this exam.

    I studied for 2 weeks. I have no professional experience. I have linux as my main desktop for last 4 years. However, I hadn’t used more than 25 commands in normal usage. LFCS raised my bar.

    • Ravi Saive says:

      Congrats bro…and thanks for appreciating our articles. The Big thank goes to our author “Gabriel Cánepa” for writing such useful out-of-the-box articles on LFCS series… I hope others too get benefit out of it..

      • Ashish says:

        Thank you. Gabriel Canepa is awesome. I can see his articles everywhere (such as xmodulo.com). I have registered for LFCE exam for 25th Jan. I can see that Gabriel has already finished part 6 of 12 for LFCE preparation. I am looking forward to it.

        • @Ashish,
          I appreciate your kind comment about my work in this series and also about the LFCE series. Part 7 should be published during the next ~12 hours so stay tuned!
          Thanks for following me in xmodulo as well! You can always find my latest articles there at xmodulo/author/gabriel, and please note that I write for DigitalOcean as well (not as frequent as for Tecmint or Xmodulo, though). You can check my articles at DO here: https://www.digitalocean.com/community/users/gacanepa.

    • @Ashish,
      I am glad that this series helped you as a starting point in your preparation for the exam. You have pointed out a true point – one could not realistically expect that 10 articles cover all the contents of the certification, and even if we could, we would violate a confidentiality agreement with the Linux Foundation. I even consulted with them about the series and they said it was OK as long as I didn’t suggest what could be included, and what not, in the actual exam.
      That being said, we have also tried to emphasize on each article that readers should take the same approach as you did – start with what we give you but don’t think that it is everything that there is to know in order to pass the exam.
      Thanks for your enlightening comment and good luck in all your endeavors!

  8. @Emanuel,
    Thanks for your comment.
    Covering ALL file-related tools would take a complete series of its own. Trying to decide what to include and what to leave out, specially on this article, was a difficult decision. However, please note that since the exam is performance-based, you’re free to choose what tools to use, and in this article we have covered enough tools to create, edit, and manipulate files.
    That being said, I believe your comment is very appropriate as it points out further tools that can be used to sharpen your file management skills in preparation for the exam.

  9. Emanuel Sergio Orozco says:

    Thank you for the help.

    I don’t see the basic manipulate text files commands like cat, head, tail, touch…

    Do you already passed the LFCS exam?

  10. @lvin says:

    cud -t’ ‘ -f1,3
    This is not correct in the
    # last | grep gacanepa | tr -s ‘ ‘ | cud -t’ ‘ -f1,3 | sort -k2 | uniq.

    Any suggested book for LFCS? Thanks

    • @lvin – thanks for bringing that to our attention. That was a typo.
      That one-liner should read as follows:
      # last | grep gacanepa | tr -s ‘ ‘ | cut -d’ ‘ -f1,3 | sort -k2 | uniq
      As for a suggested book that covers the competencies for the LFCS exam, there isn’t any as of yet, since this is a brand new certification. We hope to cover in this 10-article series all the necessary domains and topics that are required as per the Linux Foundation. Feel free to check out the other parts here in TecMint.com and provide us with your valuable feedback and further questions, if you have any.
      In addition, do not hesitate to contact me at my social network profiles if you need further clarifications.

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