Text Manipulation

Question 1

How to use the sed command to find and replace all the occurences of the term ‘mysql’ for ‘MySQL’ in a file called details.conf?

Answer 1

$ sed s/mysql/MySQL/g details.conf > details.conf

Question 2

How to use the sed command to find and replace only the first occurence of the term ‘mysql’ for ‘MySQL’ in a file called details.conf?

Answer 2

$ sed s/mysql/MySQL/ details.conf > details.conf

Question 3

How to use the sed command to find and replace only the second occurence of the term ‘mysql’ for ‘MySQL’ in a file called details.conf?

Answer 3

$ sed s/mysql/MySQL/2 details.conf > details.conf

Question 4

How do you display a file with line numbers?

Answer 4

Using the nl command.

Question 5

How do you show only the first 20 lines of a file called text_file.txt?

Answer 5

$ head -20 text_file.txt

Question 6

How do you show the last 20 lines of a file called text_file.txt?

Answer 6

$ tail -20 text_file.txt

Question 7

Why is the cat command not so good to display large files?

Answer 7

Because it prints all the file at once in the console making it not so practical to glean any information from it.

Question 8

What utility does the man command use?

Answer 8

The “more” command.

Question 9

What is the difference between “more” and “less” commands?

Answer 9

Both are used to display files page by page, but less has an additional functionality that permits filtering the text for terms.

Question 10

After typing a term while seeing a file with less, how can you go to the next occurence of the searched term?

Answer 10

By pressing n.