To find the inode number of a file on Linux/Unix the following approaches can be used.
Find inode using ls
$ ls -i file1.txt 412882 file1.txt
Find inode using stat
$ stat file1.txt File: ‘file1.txt’ Size: 0 Blocks: 0 IO Block: 4096 regular empty file Device: ca01h/51713d Inode: 412882 Links: 1 Access: (0664/-rw-rw-r--) Uid: ( 1001/ gopj) Gid: ( 1001/ gopj) Access: 2016-04-16 08:17:16.218080999 +0000 Modify: 2016-04-16 08:26:18.154080999 +0000 Change: 2016-04-16 08:26:18.154080999 +0000 Birth: -
To display only inode
$ stat --format "%i" file1.txt 412882