How to join lines of two lines in linux

1. Join name command in linux

join – join lines of two files on a common field

2. Synopsis for join

join [OPTION]... FILE1 FILE2 
3. Frequently used options for join command
-j FIELD
   equivalent to `-1 FIELD -2 FIELD'
-1 FIELD
   join on this FIELD of file 1
-2 FIELD
   join on this FIELD of file 2 
4. Examples of join command

Join command can be as a simple database join table.

Suppose that we have two following files, file1:

echo -e "0001 =\n0010 =\n0011 =\n0100 =\n0101\
 =\n0111 =" | nl > file1

join - create a sample file 1

$ echo -e "one\ntwo\nthree\nfour\nfive\nsix" | nl > file2 

join - create a sample file 2
now we can use join command to join those two files:

$ join -j 1 file1 file2 

join files with join command

Source taken from http://linuxconfig.org/