Unix interview questions and answers part - 2

1. How do you rename the files in a directory with _new as suffix?

ls -lrt|grep '^-'| awk '{print "mv "$9" "$9".new"}' | sh

2. Write a command to convert a string from lower case to upper case?
echo "apple" | tr [a-z] [A-Z]

3. Write a command to convert a string to Initcap.

echo apple | awk '{print toupper(substr($1,1,1)) tolower(substr($1,2))}'

4. Write a command to redirect the output of date command to multiple files?

The tee command writes the output to multiple files and also displays the output on the terminal.

date | tee -a file1 file2 file3

5. How do you list the hidden files in current directory?

ls -a | grep '^\.'

6. List out some of the Hot Keys available in bash shell?

Ctrl+l - Clears the Screen.

Ctrl+r - Does a search in previously given commands in shell.

Ctrl+u - Clears the typing before the hotkey.

Ctrl+a - Places cursor at the beginning of the command at shell.

Ctrl+e - Places cursor at the end of the command at shell.

Ctrl+d - Kills the shell.

Ctrl+z - Places the currently running process into background.

7. How do you make an existing file empty?

cat /dev/null > filename

8. How do you remove the first number on 10th line in file?

sed '10 s/[0-9][0-9]*//' < filename

9. What is the difference between join -v and join -a?

join -v : outputs only matched lines between two files.

join -a : In addition to the matched lines, this will output unmatched lines also.

10. How do you display from the 5th character to the end of the line from a file?

cut -c 5- filename