Unix Shell Fields Processing: cut

1. cut: select fields

test:
Note: there are 2 spaces between "XX" and "Male"

 #! /bin/bash  
 Name Sex Cell#  
 XX  Male 0000000000  
 YY Female 0000000101  

terminal:
Select the first filed of ./test
-d " ", means we are using "one space" as the delimiter, in this case:
first line of ./test: two fields: "#!" and "/bin/bash"
second line of ./test, three fields: "Name", "Sex" and "Cell#"
third line of ./test, four fields: "XX", null, "Male" and "000000000", because we have two spaces between "XX" and "Male", which generate one "null" as the second field
fourth line of ./test, three fields: "YY", "Female", and "000000101"
-f 1 means: we are going to select the first field of each line.

 aubinxia@aubinxia-VirtualBox:~/Desktop/xxdev$ cut -d " " -f 1 ./test  
 #!  
 Name  
 XX  
 YY  

select other specific field:
First command: third line is empty because 2nd field of third line is empty as explained above.
second command: first line is empty because there are only 2 fields in the first line.

 aubinxia@aubinxia-VirtualBox:~/Desktop/xxdev$ cut -d " " -f 2 ./test  
 /bin/bash  
 Sex  

 Female  
 aubinxia@aubinxia-VirtualBox:~/Desktop/xxdev$ cut -d " " -f 3 ./test  

 Cell#  
 Male  
 0000000101  

select 4th field: only third line return 4th field, since all other lines have only 3 fields each.

 aubinxia@aubinxia-VirtualBox:~/Desktop/xxdev$ cut -d " " -f 4 ./test  


 0000000000  

select field 1 to field 3 of each line: -f 1-3 means a range.

 aubinxia@aubinxia-VirtualBox:~/Desktop/xxdev$ cut -d " " -f 1,2,3 ./test  
 #! /bin/bash  
 Name Sex Cell#  
 XX Male  
 YY Femail 0000000101  
 aubinxia@aubinxia-VirtualBox:~/Desktop/xxdev$   
 aubinxia@aubinxia-VirtualBox:~/Desktop/xxdev$ cut -d " " -f 1-3 ./test  
 #! /bin/bash  
 Name Sex Cell#  
 XX Male  
 YY Femail 0000000101  

2. cut: use different delimiters
test:
If using ":" as delimiter, then:
1st line: 3 fields: "Name", "Male", "Cell#"
2nd line: 4 fields: "XX",null, "Male", "0000000000"
3rd line: 3 fields "    YY"(note the space here), "Female", "0000000101"

 Name:Sex:Cell#  
 XX::Male:0000000000  
   YY:Female:0000000101  

terminal:
1st command: select first 3 fields, note the 2nd line, because we have one "null" object as the second field, so it stopped at "Male"
Note the 3rd line, using ":" as the delimiter, the first field's spaces are counted as part of field

2nd command, select 4th field, only 2nd line has 4 fields, so only 2nd line get outputted.

 aubinxia@aubinxia-VirtualBox:~/Desktop/xxdev$ cut -d ":" -f 1-3 ./test  
 Name:Sex:Cell#  
 XX::Male  
   YY:Female:0000000101  
 aubinxia@aubinxia-VirtualBox:~/Desktop/xxdev$ cut -d ":" -f 4 ./test  

 0000000000  

3. cut: select specific count of characters
test is same as above

terminal:
select 1st character of each line: the 3rd line is empty because third line start with a white space

 aubinxia@aubinxia-VirtualBox:~/Desktop/xxdev$ cut -c 1 ./test  
 N  
 X  

select first 5 characters of each line:

 aubinxia@aubinxia-VirtualBox:~/Desktop/xxdev$ cut -c 1-5 ./test  
 Name:  
 XX::M  
   Y  

select more characters than each line has, it will stop at the end of line automatically:

 aubinxia@aubinxia-VirtualBox:~/Desktop/xxdev$ cut -c 1-100 ./test  
 Name:Sex:Cell#  
 XX::Male:0000000000  
   YY:Female:0000000101  

Select first 10 characters(permissions) of each line of "ls -lrt"

 aubinxia@aubinxia-VirtualBox:~/Desktop/xxdev$ ls -lrt | cut -c 1-10  
 total 448  
 -rwxrwxr-x  
 -rwxrwxr-x  
 -rw-rw-r--  
 -rwxrwxr-x  
 -rw-rw-r--  
 drwxrwxr-x  
 -rw-rw-r--  
 -rw-rw-r--  
 -rwxrwxr-x  
 -rwxrwxr-x