Linux/Unix sort command examples

This is a small tutorial on how to use sort command to sort a file. Sorting is very useful when dealing with DB files, CSV, xls, log files in fact a text file too. By default sort command will sort according to alphabets. First sort tries to sort according to single character, if it finds the first character same in two lines, then it moves to sort second character. Suppose I have a following word list in a file

cat filename.txt
abc
cde
hij
klm
kle
ble

This will be sorted first with first char. When it finds both the char same in this example klm and kle start with same characters, so it tries to sort with third character which is different in them. The output of sort  as below

sort filename.txt

abc

ble

cde

hij

kle

klm