please advice how it can be - ( this action was on linux machine )
why the string - "append" that I add with echo is after the line "spb_IP=172.17.100.122"
and not under the line - "spb_IP=172.17.100.122" ????
more file
spa_IP=172.17.100.121 spb_IP=172.17.100.122 echo "append" >> file
more file
spa_IP=172.17.100.121 spb_IP=172.17.100.122append this This will be because the file does not end in a \n.
hexdump -C file 00000000 73 70 61 5f 49 50 3d 31 37 32 2e 31 37 2e 31 30 |spa_IP=172.17.10| 00000010 30 2e 31 32 31 0a 73 70 61 5f 49 50 3d 31 37 32 |0.121.spa_IP=172| 00000020 2e 31 37 2e 31 30 30 2e 31 32 32 |.17.100.122| Note the file ends in 0x32 which is ASCII for 2
When you append to it it becomes
hexdump -C file 00000000 73 70 61 5f 49 50 3d 31 37 32 2e 31 37 2e 31 30 |spa_IP=172.17.10| 00000010 30 2e 31 32 31 0a 73 70 61 5f 49 50 3d 31 37 32 |0.121.spa_IP=172| 00000020 2e 31 37 2e 31 30 30 2e 31 32 32 61 70 70 65 6e |.17.100.122appen| 00000030 64 0a Note that as you have observed the 122 runs straight into the append 122append
To fix your 'problem' you need to
echo -e "\nappend" to add the missing \n.
hexdump -C file 00000000 73 70 61 5f 49 50 3d 31 37 32 2e 31 37 2e 31 30 |spa_IP=172.17.10| 00000010 30 2e 31 32 31 0a 73 70 61 5f 49 50 3d 31 37 32 |0.121.spa_IP=172| 00000020 2e 31 37 2e 31 30 30 2e 31 32 32 0a 61 70 70 65 |.17.100.122.appe| 00000030 6e 64 0a |nd.| Now there is a . between the 122 and the append which represents the 0x0a (ASCII line Feed) character.