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viyashdoss
viyashdoss

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CLI - commands and their uses

1)What is the difference between Service and Application?

  • Service(API) is a kind of work/process which is mostly used by other programs, whereas Application(Software) is a service offered to the user or any other application to manage the process/work.



2)What are these wildcards ~, ., .., * and ??

  • Wildcards are special characters which are used to ease the search process. It is used for identifying multiple items but not identical data.
    • ~ Home directory
    • . Current working directory
    • .. Prev to the current directory
    • * Any number of characters.



3)What are the different flags for the kill? Why do we use kill -9 in general?

  • Kill command is used to kill the process in Linux systems but also we can use it to halt/interrupt/continue the process. To do that we can use the command

kill SignalName/ID PID

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4)Are you clear about file permissions? Explain them. chmod and chown commands?

  • CHMOD cmd is used to alter the permission(Read, Write, Execute) of the file. Two different ways of representation.

    • Absolute - CHMOD 755 file.txt
    • Symbolic - CHMOD a=rwx file.txt
  • CHOWN cmd is used to update the user/group of the file.

    • To update the user - Sudo CHOWN user filename
    • To update user & group - Sudo CHOWN user: group filename



5)Usage of Ctrl+R to search previously run commands, arrow keys and tab autocompletion.

  • Tab - Autocomplete the word based on what we have typed.
  • Arrow Keys - up/down keys Navigate to frequently used commands.
  • CTRL+R - It's like a search box to find the previously ran command.

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