Mislav Jurić

Tag: command

  • Linux Tutorial Series – 69 – The file command

    Here is the video version, if you prefer it:

    The file command is used to guess the filetype based on files contents. (Ward, 2014)⁠

    Here is an example of its usage:

    mislav@mislavovo-racunalo:~/Documents$ file ls.txt

    ls.txt: UTF-8 Unicode text

    Hope you learned something new!

    References

    Ward, B. (2014). How Linux Works: What Every Superuser Should Know (2nd ed.). No Starch Press. Page 20

  • Linux Tutorial Series – 68 – The tee command

    Here is the video version, if you prefer it:

    The tee command is used to redirect standard output to both standard output and one or more files. (Shotts, 2019)⁠ Here is an example of its usage:

    mislav@mislavovo-racunalo:~/Documents$ ls | tee ls.txt | grep test

    test.txt

    mislav@mislavovo-racunalo:~/Documents$ cat ls.txt

    001_002.pdf

    Accounti

    AGI safety podcasti

    ...

    I never used it, but it is very useful to check the output intermediary steps in long pipes.

    Hope you learned something useful!

    References

    Shotts, W. (2019). The Linux Command Line, Fifth Internet Edition. Retrieved from http://linuxcommand.org/tlcl.php. Pages 89-90

  • Linux Tutorial Series – 67 – apropos, whatis and info – commands I never used

    Here is the video version, if you prefer it:

    Hello there,

    I wanted to introduce you to 3 commands I never used, but may come in handy in some cases (although so far I have never encountered them).

    The first is apropos. It is used to find commands appropriate for something. I use Google for this task.

    The second is whatis. It is used for short, one-line command descriptions. I use --help or (much less frequently) man. Much more frequently, I use Google to find out what the command does.

    The last command on the list is info. I use man over info and Google over man. To add something here – I have seen some instances where people recommend checking out info pages (accessed through the info command), but that is recommended in an answer on StackOverflow which gives the answer and then suggests looking at the info pages.

    There you have it – the commands and the alternatives I use. One of them is Google, but hey, if you are on a desert island and you simply must figure out what command is appropriate for something, use apropos.

    Thank you for reading! Hope you learned something useful.

  • Linux Tutorial Series – 66 – The alias command

    Here is the video version, if you prefer it:

    The alias command is used to construct your own commands which are made out of existing commands. (Shotts, 2019)⁠ Here is an example of how it is used:

    mislav@mislavovo-racunalo:~$ alias ll='ls -l'

    mislav@mislavovo-racunalo:~$ ll

    total 76

    drwxr-xr-x 27 mislav mislav 4096 Sep 19 14:00 anaconda3

    drwxr-xr-x 26 mislav mislav 4096 Dec 30 00:40 'Calibre Library'

    drwxr-xr-x 2 mislav mislav 4096 Aug 25 12:21 Desktop

    drwxr-xr-x 26 mislav mislav 4096 Jan 16 09:38 Documents

    …

    Its syntax is as follows:

    alias name='string'

    Be wary of the spaces – there are no spaces between name, = and ‘ ‘!

    As you can see, you can create your own commands with alias. More specifically, you are creating an alias for an existing (or a sequence of existing) commands – hence the name.

    Some notes: make sure not to alias an existing command name (check if the command name is used already with the type command). Also, the alias you create will vanish when you exit your Terminal session. That is a topic for another post.

    Hope you learned something useful!

    References

    Shotts, W. (2019). The Linux Command Line, Fifth Internet Edition. Retrieved from http://linuxcommand.org/tlcl.php. Page 74-76

  • Linux Tutorial Series – 65 – Executing multiple commands on the same line

    Here is the video version, if you prefer it:

    You can execute multiple commands on the same line. To do that, you need to add a semicolon, like so: (Shotts, 2019)⁠

    command1; command2; command3

    An example:

    cd /; ls; cd

    This lists the contents of the root directory and then switches your working directory back to your home directory.

    Hope you learned something new!

    References

    Shotts, W. (2019). The Linux Command Line, Fifth Internet Edition. Retrieved from http://linuxcommand.org/tlcl.php. Page 74

  • Linux Tutorial Series – 64 – The which command

    Here is the video version, if you prefer it:

    The which command shows you the location of a given executable. (Shotts, 2019)⁠ For example:

    mislav@mislavovo-racunalo:~/Linux_folder$ which cp

    /usr/bin/cp

    It only works for executables, not for other command types.

    Hope you learned something useful!

    References

    Shotts, W. (2019). The Linux Command Line, Fifth Internet Edition. Retrieved from http://linuxcommand.org/tlcl.php. Pages 67-68

  • Linux Tutorial Series – 63 – The type command

    Here is the video version, if you prefer it:

    The type command displays the command’s type. (Shotts, 2019) Here is how it is used:

    ⁠mislav@mislavovo-racunalo:~/Linux_folder$ type ls

    ls is aliased to `ls --color=auto'

    mislav@mislavovo-racunalo:~/Linux_folder$ type mv

    mv is /usr/bin/mv

    mislav@mislavovo-racunalo:~/Linux_folder$ type cp

    cp is /usr/bin/cp

    mislav@mislavovo-racunalo:~/Linux_folder$ type echo

    echo is a shell builtin

    mislav@mislavovo-racunalo:~/Linux_folder$ type cd

    cd is a shell builtin

    So ls is an alias, mv and cp are executables and echo and cd are shell builtins.

    Hope you learned something new!

    References

    Shotts, W. (2019). The Linux Command Line, Fifth Internet Edition. Retrieved from http://linuxcommand.org/tlcl.php. Page 67

  • Linux Tutorial Series – 62 – Command types

    Here is the video version, if you prefer it:

    There are 4 types of Linux commands (Shotts, 2019)⁠:

    • executable programs (called executables for short) – programs that are written in a programming language (either a so-called compiled programming language or an interpreted programming language)
    • a command built into the shell itself (shell builtin) (such as echo)
    • shell functions (miniature shell scripts)
    • aliases (commands which we define ourselves which are composed of other commands)

    Why is this useful to know? Well, let’s say that you type in ll into your Terminal and get the following error:

    mislav@mislavovo-racunalo:~/Linux_folder$ ll

    bash: ll: command not found

    Ooops! What just happened? bash tells me it didn’t find the command ll. How could this be? Well, it is because ll is an alias for ls -l, which I can execute:

    mislav@mislavovo-racunalo:~/Linux_folder$ ls -l

    total 20

    -rw-r--r-- 1 mislav mislav 63 Jan 13 05:17 aba.txt

    -rw-r--r-- 1 mislav mislav 0 Jan 11 23:00 aba.txt~

    -rw-r--r-- 1 mislav mislav 12 Jan 13 05:17 ab.txt

    -rw-r--r-- 1 mislav mislav 0 Jan 11 23:00 ab.txt~

    -rw-r--r-- 1 mislav mislav 26 Jan 13 05:18 a.txt

    -rw-r--r-- 1 mislav mislav 0 Jan 11 23:00 a.txt~

    -rw-r--r-- 1 mislav mislav 40 Jan 13 05:18 cb.txt

    -rw-r--r-- 1 mislav mislav 0 Jan 11 23:00 cb.txt~

    -rw-r--r-- 1 mislav mislav 26 Jan 11 22:18 file.txt

    If I hadn’t known ll is an alias, I might have thought I am lacking some executable. Moreover, I can define my own ll alias which shortens my typing session.

    Hope you learned something useful!

    References

    Shotts, W. (2019). The Linux Command Line, Fifth Internet Edition. Retrieved from http://linuxcommand.org/tlcl.php. Page 66

  • Linux Tutorial Series – 61 – Checkpoint

    Here is the video version, if you prefer it:

    In the following articles, we will talk about command types (not all commands are of the same type), some file-related commands and searching for files.

    Searching for files is the thing you will use most often, but it pays to know what command types are there and how to see the difference between two files, for example. Make sure to pay attention to searching for files and do read through other content, but again, it isn’t going to be of that much importance.

    Talk soon!

  • Linux Tutorial Series – 60 – Recap

    Here is the video version, if you prefer it:

    A flashback – we talked about:

    Redirecting input and output:

    • ls > output.txt is an example
    • Use >> to append
    • Use &> to redirect both standard output and standard error

    Other stuff we talked about:

    • Pipelines are used to redirect standard output of one command to the standard input of the other command; usage: command1 | command2
    • Shell globbing (wildcards) is used to match filenames before the command is executed
    • Brace expansions – something{else,else2,else3} (no spaces between the commas)
    • Regular expressions are used to match patterns in text; for example, a* means match the character a zero or more times

    Hope you refreshed your memory!