Quick Answer: What Does The Command Echo $$ Print In A Bash Shell?

What is the echo command in bash?

echo is one of the most commonly and widely used built-in command for Linux bash and C shells, that typically used in scripting language and batch files to display a line of text/string on standard output or a file..

What is $1 in bash shell?

$1 is the first command-line argument passed to the shell script. Also, know as Positional parameters. … $0 is the name of the script itself (script.sh) $1 is the first argument (filename1) $2 is the second argument (dir1)

What is the command to review the contents of a file?

The cat command is the simplest way to view the contents of a file. It displays the contents of the file(s) specified on to the output terminal. Sometimes, we might want to number the lines in the output. Note that the line numbering starts from 1.

Which Amazon Echo has the best sound?

1. Amazon Echo Dot with Clock. Of all the best Alexa speakers, the Amazon Echo Dot with Clock is our favorite. Not only does the spherical shape of the device improve the fullness of the Echo Dot’s sound compared to the 3rd-generation model, but it makes the display a bit easier to read, too.

Do you need an Amazon account to use Alexa?

You need an Amazon account to use Alexa, but you don’t need Amazon Prime. Sign in on the app. … Here you can add any number of Alexa-supported devices to your account, from smart lights to smart plugs. But we’re focused on Echo devices, so tap Amazon Echo; at the next screen, tap the Echo device you want to set up.

What is printf in bash?

“printf” command in Linux is used to display the given string, number or any other format specifier on the terminal window. It works the same way as “printf” works in programming languages like C. Note: printf can have format specifiers, escape sequences or ordinary characters.

Which is better Amazon echo or dot?

Basically, the only difference between the two devices, other than size and cost, is sound. If you’re just looking to be introduced to Alexa, you’ll be fine with the Echo Dot. It has all the smarts of Alexa in a small speaker. … All in all, the Echo Dot is an ideal choice for most people.

What is Echo $1?

$1 is the argument passed for shell script. … But if you’ll write and run your own script in current session, $1, $2, … will be parameters that you send to your script.

What is difference between Bash and Shell?

Bash ( bash ) is one of many available (yet the most commonly used) Unix shells. … Shell scripting is scripting in any shell, whereas Bash scripting is scripting specifically for Bash. In practice, however, “shell script” and “bash script” are often used interchangeably, unless the shell in question is not Bash.

What is $0 bash?

$0. $0 bash parameter is used to reference the name of the shell or shell script. so you can use this if you want to print the name of shell script. $- $- (dollar hyphen) bash parameter is used to get current option flags specified during the invocation, by the set built-in command or set by the bash shell itself.

How do I increment a variable in bash?

The most simple way to increment/decrement a variable is by using the + and – operators. This method allows you increment/decrement the variable by any value you want.

What are the bash commands?

Top 25 Bash CommandsQuick note: Anything encased in [ ] means that it’s optional. … ls — List directory contents.echo — Prints text to the terminal window.touch — Creates a file.mkdir — Create a directory.grep — search.man — Print manual or get help for a command.pwd — Print working directory.More items…•

What does echo $$ do?

Expands to the exit status of the most recently executed foreground pipeline. echo $? will return the exit status of last command. You got 127 that is the exit status of last executed command exited with some error (most probably).

How do I echo a variable in bash?

Now, using the echo command we can simply display its value on the terminal as follows:$ var_a=100. $ echo $var_a.$ var_b=” bash programming echo variable” $ echo $var_b.$ var_A=”hellofriends” $ var_B=50. $ echo $var_A$var_B.$ var1=$(date) $ var2=$(hostname) $ echo “the date is $var1 @ computer name is $var2”

What’s the difference between Alexa and echo?

Alexa is specifically the name of the virtual assistant – the disembodied voice you talk to, ask questions, and bug with song requests. Amazon’s Echo is simply the name given to the physical products themselves, the speakers which house the AI Alexa. … For more information see our list of Alexa compatible devices.

Is there a monthly charge for using the Amazon Echo?

No, the Amazon Echo requires no monthly service fee, but it is important to note that when you register your Amazon Echo for the first time, you will get 1 free month of Amazon Prime, which includes Amazon Prime Music (the default Amazon Echo Music Service).

What command lets you view all the commands you’ve used?

In Linux, there is a very useful command to show you all of the last commands that have been recently used. The command is simply called history, but can also be accessed by looking at your . bash_history in your home folder. By default, the history command will show you the last five hundred commands you have entered.

How do you echo quotes in bash?

Use a backslash: echo “\”” # Prints one ” character. It’s done by finishing an already-opened one ( ‘ ), placing the escaped one ( \’ ), and then opening another one ( ‘ ). It’s done by finishing already opened one ( ‘ ), placing a quote in another quote ( “‘” ), and then opening another one ( ‘ ).