Regular Expressions and grep exercises (Linux)

1, in the current system create user student Student1 Student2, find the current system named student (must appear at the beginning) of the user's account and related information, the file is/etc/passwd

grep "^student\>"/etc/passwd | Cut-d:-F3

2, analyze the following text in the/etc/inittab file the characteristics of the first two lines (where the number must be the same in each line), write a pattern that can be found exactly like two lines:

11:1:WAIT:ETC/RC.D/RC 1

13:3:WAIT:ETC/RC.D/RC 3

grep "^1\ ([0-9]\): \1.*\1$"/etc/inittab

3, displays all files that end with a number and do not contain white space in the file name

LS *[^[:space:]]*[0-9] File name

4. Find the number between 1-255 in the/boot/grub/grub.conf file

\< ([1-9]|[ 1-9][0-9]|1[0-9][0-9]|2[0-4][0-9]|25[0-5]) \>

Regular Expressions and grep exercises (Linux)