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Tuesday, March 19, 2013

Unix Real Time Interview Questions with answers


1. Display all the files in current directory sorted by size?
ls -l | grep ‘^-’ | awk ‘{print $5,$9}’ |sort -n|awk ‘{print $2}’

2. Write a command to search for the file ‘map’ in the current directory?
find -name map -type f

3. How to display the first 10 characters from each line of a file?
cut -c -10 filename

4. Write a command to remove the first number on all lines that start with “@”?
sed ‘\,^@, s/[0-9][0-9]*//’ < filename

5. How to print the file names in a directory that has the word “term”?
grep -l term *
The ‘-l’ option make the grep command to print only the filename without printing the content of the file. As soon as the grep command finds the pattern in a file, it prints the pattern and stops searching other lines in the file.

6. How to run awk command specified in a file?
awk -f filename

7. How do you display the calendar for the month march in the year 1985?
The cal command can be used to display the current month calendar. You can pass the month and year as arguments to display the required year, month combination calendar.
cal 03 1985
This will display the calendar for the March month and year 1985.

8. Write a command to find the total number of lines in a file?
wc -l filename
Other ways to pring the total number of lines are
awk ‘BEGIN {sum=0} {sum=sum+1} END {print sum}’ filename
awk ‘END{print NR}’ filename

9. How to duplicate empty lines in a file?
sed ‘/^$/ p’ < filename

10. Explain iostat, vmstat and netstat?
  • Iostat: reports on terminal, disk and tape I/O activity.
  • Vmstat: reports on virtual memory statistics for processes, disk, tape and CPU activity.
  • Netstat: reports on the contents of network data structures.

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