1. wc : print newline, word, and byte counts for each file
[root@bogon ~]# wc /etc/passwd
44 88 2301 /etc/passwd
-l: lines
-w: words
-c: characters
2. cut : remove sections from each line of files
2.1 Commondly used options
-d DELIMITER: specify the delimiter
-f FILEDS:
#: filed #
#,#[,#]：Discrete(离散的) multiple filed，such as 1,3,6
#-#：Consecutive(连续的) fields, such as 1-6
a mixture use of -f ：1-3,7
--output-delimiter=STRING : specify the delimiter when print contents.
2.2 example
[root@bogon ~]# cut -d' ' -f 1 /etc/fstab
The space key as the delimiter，print filed 1
[root@bogon ~]# cut -d: -f1 /etc/passwd
[root@bogon ~]# cut -d: -f1-7 /etc/passwd
[root@bogon ~]# cut -d: -f1-4 --output-delimiter='--' /etc/passwd //specify output delimiter
3. sort : sort lines of text files
3.1 Commondly used options
-f: ignore case
-r: sort in reverse
-t DELIMITER: delimiter
-k #：Sort by specified filed, and sort by ASCII by default
-n: sort by numerical value
-u: uniq，omit repeated lines after sorting
3.2 example
[root@bogon ~]# sort /etc/passwd
[root@bogon ~]# sort -t: -k3 /etc/passwd
4. uniq : report or omit repeated lines
4.1 repeat ： continues and equal is repeat
4.2 uniq can only omit repeated lines and cannot sort. sort -u omit repeated lines and sort at the same time.
4.3 Commondly used options
-c: print the number of repeated lines
-d: Only print repeated lines
-u: Only print lines that do not repeated.
5. exerciese ：Seperated by colon,and take lines 6 to 10 of the /etc/passwd file and sort the information by numerical value of the third field , then only show the first field.