To return all the female employees in their 30's, you can use the following SQL command:

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SELECT * FROM employees
WHERE gender = 'female' AND age >= 30 AND age < 40;

This command uses the SELECT statement to fetch all columns (*) from the employees table. The WHERE clause filters the result by gender (female) and age (>= 30 and < 40).

Please note that you may need to modify the table name and column names based on your database schema.

node -v is a command that checks the version of Node.js that is currently installed on your computer. This command returns the version number in the terminal. Node.js is a JavaScript runtime that allows developers to run JavaScript on the server side.

Here is an example of using the node -v command:

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node -v

This command will output the version of Node.js installed on your computer, for example v14.15.0.

To downgrade your npm version, you need to use the following command on your terminal:

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npm install -g npm@<desired-version>

Replace <desired-version> with the version you want to install down to. For example, if you want to downgrade to version 6.14.10, your terminal command would be:

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npm install -g npm@6.14.10

This will install the specified version of npm globally on your machine.

To stop npm from running in the terminal, you can typically use the CTRL + C keyboard shortcut. This will interrupt any currently running npm scripts or commands.

Example:

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^C

This will stop npm from running in the terminal.

Preconnect is a command that tells the browser to establish early connections before an HTTP request is made. By preconnecting to the host, the browser can set up the necessary sockets ahead of time, eliminating extra round trips and saving time.

For example, in HTML, you can use the <link rel="preconnect" href="[url]"> command to tell the browser to connect to a given URL before any requests are required from it.

The following code connects the browser to a given website's origin before any requests:

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<!-- Connect to the origin before any requests -->
<link rel="preconnect" href="https://example.com" crossorigin>

For more information about preconnect, check out this guide: https://web.dev/uses-rel-preconnect/

AcuCOBOL is an imperative, procedural COBOL language. The GOBACK command is used for program flow control. It returns the program control to the main block.

For example:

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   PERFORM Test-Block
   GOBACK

Test-Block.
   DISPLAY "This is a test block"
   END-PERFORM

In the above example, the PERFORM command will jump to the Test-Block section of the code. Once the end of the Test-Block is hit, the GOBACK command will send control back to the PERFORM statement after the Test-Block code block. This allows the code to repeat the code in the Test-Block block every time the GOBACK command is called.

You can open a folder in VSCode by:

1. Opening VSCode
2. Clicking "File"
3. Selecting "Open" and then selecting the folder you want to open Or by running this command in your terminal: code <folder path>

In Linux, the cron job for backing up the /var/log/auth.log file could look like this:

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0 1 * * * /bin/cp -p /var/log/auth.log /root/auth-log-backup/

This cron job will copy the /var/log/auth.log file to the /root/auth-log-backup directory every morning at 1AM.

Underlines on links can be enabled or disabled by CSS styles. Depending on the browser, the exact command used may vary, but a typical command to enable the underline is text-decoration: underline. You can add or remove this in the CSS stylesheet or style tag of the webpage.

In the VSCode terminal, use the cd command to navigate to the folder that contains the package.json file of the React project, then install the axios package with npm install axios or yarn add axios.

The calc command is a Unix command that allows you to perform simple calculations from the command line. It can be used to calculate basic arithmetic operations, such as addition, subtraction, multiplication and division, as well as to compare numbers and evaluate mathematical functions. For example, calc 2 + 2 will return the result 4. For more information about calc, refer to the man page.