Bourne Again Shell Session Linux Command

Welcome to our ultimate guide to the Linux Command Line. This tutorial will show you lot some of the central Linux command line technologies and introduce yous to the Bash scripting language.

What is Bash?

Fustigate (short for Bourne Again SHell) is a Unix vanquish, and a command language interpreter. A shell is simply a macro processor that executes commands. Information technology's the virtually widely used shell packaged by default for near Linux distributions, and a successor for the Korn shell (ksh) and the C trounce (csh).

Many things that can be done Linux operating organisation can exist washed via control line. Some examples are…

• Editing files
• Adjusting the volume of the operating organisation
• Fetching web pages from the internet
• Automating work you do every day

Y'all tin read more about bash here, via the GNU Documentation, and via the tldp guide.

Using fustigate on the command line (Linux, Bone X)

You tin start using bash on most Linux and Bone X operating systems past opening upwardly a terminal. Allow's consider a uncomplicated hello globe instance. Open up your terminal, and write the following line (everything afterwards the $ sign):

                zach@marigold:~$ echo "Hello world!" Hi world!              

As you can see, we used the echo command to print the string "Hello globe!" to the final.

Writing a bash script

You can also put all of your bash commands into a .sh file, and run them from the command line. Say you had a bash script with the following contents:

                #!/bin/bash repeat "Hullo world!"              

It's worth noting that first line of the script starts with #!. It is a special directive which Unix treats differently.

Why did we use #!/bin/bash at the beginning of the script file?

That is because information technology is a convention to let the interactive shell know what kind of interpreter to run for the plan that follows. The starting time line tells Unix that the file is to exist executed by /bin/bash. This is the standard location of the Bourne beat on but about every Unix system. Adding #!/bin/bash as the commencement line of your script, tells the Os to invoke the specified shell to execute the commands that follow in the script. #! is often referred to as a "hash-blindside", "she-bang" or "sha-bang". Though it is only executed if you run your script equally an executable. For case, when you type ./scriptname.extension, it will await at the top line to observe out the interpreter, whereas, running the script as bash scriptname.sh, first line is ignored.

And so you could run the script like so: For make file executable you lot should phone call this command nether sudo chmod +10 "filename".

                zach@marigold:~$ ./myBashScript.sh Hello world!              

The script only has two lines. The showtime indicates what interpreter to use to run the file (in this example, fustigate). The second line is the command we want to use, echo, followed by what we want to print which is "Hello World".

Sometimes the script won't be executed, and the above command will return an mistake. It is due to the permissions set on the file. To avert that use:

                zach@marigold:~$ chmod u+x myBashScript.sh              

So execute the script.

Linux Command Line: Bash True cat

Cat is ane of the well-nigh frequently used commands in Unix operating systems.

Cat is used to read a file sequentially and print it to the standard output. The name is derived from its function to con cat enate files.

Usage

                cat [options] [file_names]              

Most used options:

• -b, numer non-blank output lines
• -north, number all output lines
• -s, squeeze multiple adjacent bare lines
• -five, display nonprinting characters, except for tabs and the end of line character

Example

Print in terminal the content of file.txt:

                cat file.txt              

Concatenate the content of the two files and display the outcome in last:

                cat file1.txt file2.txt              

Linux Command Line: Bash cd

Change Directory to the path specified, for case cd projects.

In that location are a few really helpful arguments to assistance this:

• . refers to the current directory, such as ./projects
• .. can be used to move upward one folder, use cd .., and tin be combined to motion up multiple levels ../../my_folder
• / is the root of your system to reach core folders, such as system, users, etc.
• ~ is the habitation directory, normally the path /users/username. Motion dorsum to folders referenced relative to this path by including it at the showtime of your path, for example ~/projects.

Linux Command Line: Fustigate head

Head is used to print the starting time 10 lines (past default) or whatever other amount specified of a file or files. Cat is used to read a file sequentially and print information technology to the standard output.
ie prints out the unabridged contents of the entire file. - that is not e'er necessary, perhaps you just want to bank check the contents of a file to run across if it is the correct ane, or check that it is indeed non empty. The head control allows yous to view the start N lines of a file.

if more than than on file is called then the outset ten lines of each file is displayed, unless specific number of lines are specified. Choosing to display the file header is optional using the pick beneath

Usage

                head [options] [file_name(s)]              

Most used options:

• -north N, prints out the showtime Northward lines of the file(s)
• -q, doesn't print out the file headers
• -v, ever prints out the file headers

Case

                head file.txt              

Prints in terminal the first ten lines of file.txt (default)

                head -north 7 file.txt              

Prints in terminal the kickoff seven lines of file.txt

                head -q -north v file1.txt file2.txt              

Print in terminal the first v lines of file1.txt, followed past the commencement 5 lines of file2.txt

Linux Control Line: Fustigate ls

ls is a command on Unix-like operating systems to list contents of a directory, for example folder and file names.

Usage

                cat [options] [file_names]              

Most used options:

• -a, all files and folders, including ones that are hidden and start with a .
• -l, Listing in long format
• -Grand, enable colorized output.

Example:

List files in freeCodeCamp/guide/

                ls                                                                ⚬ primary CODE_OF_CONDUCT.md bin                packet.json       utils CONTRIBUTING.md    gatsby-browser.js  plugins            yarn.lock LICENSE.md         gatsby-config.js   src README.md          gatsby-node.js     static assets             gatsby-ssr.js      translations              

Linux Command Line: Bash man

Man, the abridgement of man ual, is a fustigate command used to display on-line reference manuals of the given command.

Man displays the reletive man page (short for human being ual page ) of the given command.

Usage

                human [options] [command]              

Most used options:

• -f, print a short description of the given command
• -a, display, in succession, all of the available intro manual pages contained within the manual

Instance

Display the human being page of ls:

                man ls              

Linux Command Line: Fustigate mv

Moves files and folders.

                mv source target mv source ... directory              

The offset statement is the file you lot desire to move, and the 2d is the location to motility it to.

Commonly used options:

• -f to force move them and overwrite files without checking with the user.
• -i to prompt confirmation before overwriting files.

That's all. Go forth and utilise Linux.

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Source: https://www.freecodecamp.org/news/linux-command-line-bash-tutorial/

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