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Question-1. What is BASH?
Answer-1: BASH (Bourne Again Shell) is a Unix shell and command language used for scripting and system administration.
Question-2. Who developed BASH?
Answer-2: BASH was developed by the GNU Project as a free software replacement for the Bourne Shell (sh).
Question-3. How do you create a variable in BASH?
Answer-3: Using VAR_NAME=value, e.g., name="John".
Question-4. How do you print a variable in BASH?
Answer-4: Using echo, e.g., echo $name.
Question-5. What is the difference between $VAR and ${VAR}?
Answer-5: Both reference a variable, but ${VAR} helps avoid ambiguity.
Question-6. How do you get user input in BASH?
Answer-6: Using read, e.g., read name; echo "Hello, $name".
Question-7. How do you define a function in BASH?
Answer-7: Using function myFunc() { commands; } or myFunc() { commands; }.
Question-8. How do you call a function in BASH?
Answer-8: Simply by using the function name, e.g., myFunc.
Question-9. How do you execute a BASH script?
Answer-9: Using bash script.sh or ./script.sh (if executable).
Question-10. How do you make a script executable?
Answer-10: Using chmod +x script.sh.
Question-11. What is the shebang (#!) in BASH?
Answer-11: It specifies the interpreter, e.g., #!/bin/bash at the start of the script.
Question-12. How do you use command-line arguments in BASH?
Answer-12: Using $1, $2, etc., e.g., echo "First arg: $1".
Question-13. What does $@ and $* do in BASH?
Answer-13: Both represent all command-line arguments, but $@ preserves arguments as separate words.
Question-14. How do you check if a command was successful?
Answer-14: Using $?, where 0 means success.
Question-15. How do you use an if statement in BASH?
Answer-15: if [ condition ]; then commands; fi.
Question-16. How do you check if a file exists?
Answer-16: Using [ -f filename ], e.g., if [ -f myfile ]; then echo "Exists"; fi.
Question-17. How do you check if a directory exists?
Answer-17: Using [ -d dirname ], e.g., if [ -d mydir ]; then echo "Exists"; fi.
Question-18. How do you use a for loop in BASH?
Answer-18: for i in 1 2 3; do echo $i; done.
Question-19. How do you use a while loop in BASH?
Answer-19: while [ condition ]; do commands; done.
Question-20. How do you use a case statement in BASH?
Answer-20: case $var in pattern1) commands;; pattern2) commands;; esac.
Question-21. What is the difference between = and == in BASH?
Answer-21: = is for assignment, while == is used in string comparison.
Question-22. How do you redirect output to a file?
Answer-22: Using command > file (overwrite) or command >> file (append).
Question-23. How do you redirect errors to a file?
Answer-23: Using command 2> file or command 2>> file.
Question-24. How do you redirect both output and error to a file?
Answer-24: Using command > file 2>&1.
Question-25. How do you list all environment variables?
Answer-25: Using printenv or env.
Question-26. How do you export a variable in BASH?
Answer-26: Using export VAR=value.
Question-27. What is the difference between local and export in BASH?
Answer-27: local defines variables within a function, while export makes them available to child processes.
Question-28. How do you find the path of a command?
Answer-28: Using which command or type command.
Question-29. How do you check the number of arguments passed?
Answer-29: Using $#, e.g., echo "Arguments: $#"
Question-30. How do you read a file line by line in BASH?
Answer-30: while read line; do echo $line; done < file.txt.
Question-31. What does set -e do in a script?
Answer-31: It makes the script exit immediately on error.
Question-32. What does set -x do in a script?
Answer-32: It enables debugging by printing each command before executing it.
Question-33. How do you execute a command stored in a variable?
Answer-33: Using eval, e.g., cmd="ls -l"; eval $cmd.
Question-34. How do you run a command in the background?
Answer-34: Using command &.
Question-35. How do you bring a background job to the foreground?
Answer-35: Using fg.
Question-36. How do you kill a process in BASH?
Answer-36: Using kill PID or pkill process_name.
Question-37. How do you find all running processes?
Answer-37: Using ps aux or top.
Question-38. What is the difference between > and >>?
Answer-38: > overwrites a file, while >> appends to it.
Question-39. How do you check disk usage?
Answer-39: Using df -h or du -sh folder_name.
Question-40. How do you check memory usage?
Answer-40: Using free -h.
Question-41. What does && and `
Answer-41:
Question-42. How do you search for a string in a file?
Answer-42: Using grep "pattern" filename.
Question-43. How do you replace text in a file?
Answer-43: Using sed, e.g., sed -i 's/old/new/g' file.txt.
Question-44. How do you count lines in a file?
Answer-44: Using wc -l filename.
Question-45. How do you list only directories?
Answer-45: Using ls -d */.
Question-46. How do you find the current shell?
Answer-46: Using echo $SHELL.
Question-47. How do you check if a user is root?
Answer-47: Using if [ $(id -u) -eq 0 ]; then echo "Root user"; fi.
Question-48. How do you schedule a cron job?
Answer-48: Using crontab -e and adding * * * * * command.
Question-49. How do you create an alias?
Answer-49: Using alias name='command', e.g., alias ll='ls -la'.
Question-50. How do you remove an alias?
Answer-50: Using unalias name, e.g., unalias ll.
Frequently Asked Question and Answer on BASH (Bourne Again Shell)
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