All in Unix 1. How do you select from a file (i) lines 5 to 10, (ii) second-to-l

Question

All in Unix

1. How do you select from a file (i) lines 5 to 10, (ii) second-to-last line?

2. How do you extract the names of the users from /etc/passwd after ignoring the

first 10 entries?

3. How do you display a list of all processes without the ps header line where

processes with the same name are grouped together?

4. List from /etc/passwd the UID and the user having the highest UID

5. What is the difference between a wild card and a regular expression?

6. How do these expressions differ? (i) [0-9]* and [0-9][0-9]*,

(ii) ^[^^] and ^^^.

7. How do you delete all leading and trailing spaces in all lines?

Explanation / Answer

1) sed -n 5,10p file location/name - prints lines between given range
tail -n+2 filename - prints lines from 2nd to end of file

2) tail -n+11 /etc/passwd | cut -d: -f1 - prints names of users from 11th line to end of given file

4) cat /etc/passwd | awk -F: '{print $3,$1}' | sort -n | tail -n 1 - prints the user having highest UID including user name

5) Difference between wildcard and regular expressions:

wildcard - it is a charecter used in regular expressions to increase the flexibility and search efficiency.
   examples: *,.,+,?,[]
regular expressions - these are a pattern matching system that uses wildcards and strings constructed according to pre-defined syntax rules to find desired strings in text.
   examples:
       ls *.html - lists all files end with extension html

6) awk '{$1=$1};1' < file name - prints the file with trimmed leading and trailing whitespaces.

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