How can the '$?' variable be used to check if the previous command executed successfully in a Unix/Linux system?

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The '$?' variable in Unix/Linux indicates the exit status of the last executed command, helping to determine its success or failure.

Exit Status: '$?' returns 0 if the last command was successful and a non-zero value if it failed. For example, after running 'ls', '$?' will be 0 if the command succeeded.
Conditional Execution: You can use '$?' in conditional statements. For instance, 'command && echo Success' will print 'Success' only if 'command' was successful.
Error Handling: Use '$?' to handle errors in scripts. For example, 'cp file.txt /destination/; if [ $? -ne 0 ]; then echo 'Copy failed'; fi' checks if the copy command succeeded.
Chaining Commands: You can chain commands based on success or failure using '$?'. For example, 'mkdir new_folder; echo $?; rm new_folder; echo $?' shows the exit status of both commands.

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