You're reviewing a shell script and notice that it uses a loop to process command-line arguments. Which special variable in shell scripting is typically used to handle this scenario?
- $@
- $*
- $1
- $ARG
In shell scripting, the special variable $@ is typically used to handle command-line arguments. It represents all the arguments passed to the script as an array. Using $@ allows you to iterate through and process each argument in a loop.
You have been tasked to allow only a specific IP address to connect to your SSH server. Which tool or method would be best suited to achieve this?
- iptables
- /etc/ssh/sshd_config
- TCP Wrappers
- /etc/hosts.allow
To allow only a specific IP address to connect to your SSH server, you can use TCP Wrappers. You can configure access control for SSH by adding the allowed IP address in the /etc/hosts.allow file, specifying the service you want to control, which in this case is SSH.
If you wanted to rate limit incoming SSH connections using iptables, which module would be most appropriate?
- -m limit
- -m state
- -m connlimit
- -m ssh
To rate limit incoming SSH connections using iptables, the most appropriate module is -m connlimit. This module allows you to set limits on the number of connections established within a specified time frame. It's useful for mitigating brute-force attacks on SSH.
Which network file system allows sharing files and printers among Linux and Windows systems?
- Samba
- NFS
- CIFS
- FTP
Samba is the network file system that allows sharing files and printers among Linux and Windows systems. It enables Linux systems to interact seamlessly with Windows networks, sharing resources across the platforms.
What does the $# variable represent in a shell script?
- The number of arguments passed to the script
- The exit status of the previous command
- The process ID of the script
- The current working directory
The $# variable in a shell script represents the number of arguments passed to the script. This is useful for determining how many arguments were provided when calling the script and for performing conditional logic based on the number of arguments.
To check for equality without considering the type in JavaScript, you should use ______.
- === (Triple Equals)
- == (Double Equals)
- #NAME?
- !== (Not Equals)
In JavaScript, the "===" operator, known as the triple equals operator, is used to check for equality without considering the data types of the operands. It ensures both the value and the type of the operands are identical.
What challenge is commonly associated with callback functions in asynchronous JavaScript?
- Synchronous execution
- Callback hell
- Memory leaks
- Variable scope
Callback hell is a common challenge in asynchronous JavaScript. It occurs when you have multiple nested callbacks, making the code hard to read and maintain. This situation can lead to callback hell, where code becomes difficult to manage and understand.
How can the issues related to memory leaks due to closures be mitigated in JavaScript?
- Using WeakMaps
- Increasing Closure Scope
- Avoiding Closures
- Garbage Collection
Memory leaks due to closures can be mitigated by using WeakMaps in JavaScript. WeakMaps are a data structure that allows objects to be held weakly, meaning they won't prevent objects from being garbage collected. This helps in preventing memory leaks that can occur when closures hold references to objects longer than necessary.
When different classes have methods of the same name, this is referred to as method _________.
- overriding
- overloading
- overloading
- overriding
When different classes have methods of the same name with different parameters, this is referred to as "method overloading." Method overloading allows a class to have multiple methods with the same name but different parameter lists.
How might the use of immediately-invoked function expressions (IIFE) impact the performance of a JavaScript application?
- IIFE can significantly improve performance by reducing global variable usage.
- IIFE has no impact on performance; it's purely a coding style choice.
- IIFE can slow down performance due to excessive function calls.
- IIFE can lead to memory leaks in JavaScript applications.
The use of IIFE in JavaScript can have a positive impact on performance. By encapsulating code within an IIFE, you reduce the use of global variables, which can lead to fewer naming conflicts and better performance. IIFE is commonly used for encapsulating code safely and efficiently. It's not a performance bottleneck but rather a coding pattern for better code organization.