How to find the filesystem type of an USB key to mount it correctly?

I have to mount a old USB key formatted with FAT filesystem. The mount must be executed automatically by a udev rule which executes a bash script. When the USB key is inserted in the USB port, the script, for now, executes the command:

blkid -o udev /dev/sda1

where /dev/sda1 is the partition present inside the USB and formatted with FAT32 (or FAT16) filesystem. The output of the previous command for the USB key **is empty**. The output of the same command (blkid) for other USB keys contains the udev variable ID_FS_TYPE; possible values of ID_FS_TYPE are: vfat, ntfs, exfat. So an empty output for the execution of blkid happens only for this old USB and I'm not able to know why it happens only for it. ### Different options for mount command if the filesystem is vfat ### If the value of the variable ID_FS_TYPE is vfat the script must execute the following mount command:

> mount -o rw,relatime,users,gid=100,umask=000,shortname=mixed,utf8=1,flush /dev/sda1 /mount/point

While if the filesystem is not vfat the options for the mount command can be the following:

mount -o rw,relatime /dev/sda1 /mount/point

With the particular USB key (1 GB and very old) the script by the command blkid, can't determine that the filesystem type is vfat so it executes the second mount command; the result is that the permissions for the mount point directory (called /media/sda1) are:

> ls -l /media/    
total 16
drwxr-xr-x 3 root root 16384 Jan  1  1970 sda1

while I need:

# ls -l /media/    
total 16
drwxrwxrwx 3 root root 16384 Jan  1  1970 sda1

I need those permissions because **all users must be able to write on the USB** and not only the proprietary (that is root in my context). ### Find file system type by other commands ### [This link](https://unix.stackexchange.com/questions/53313/how-to-show-the-filesystem-type-via-the-terminal) gives other tips to get the filesystem type of this particular USB key. So I have tried other commands: - lsblk -n -o FSTYPE /dev/sda1: also in this case, for my specific USB key, the output of the command is empty - the output of the command file -sL /dev/sda1 instead is very long; I show this output below:

> file -sL /dev/sda1
/dev/sda1: DOS/MBR boot sector, code offset 0x3c+2, OEM-ID "MSDOS5.0", sectors/cluster 32, reserved sectors 8, root entries 512, Media descriptor 0xf8, sectors/FAT 240, sectors/track 63, heads 255, hidden sectors 2048, sectors 1966080 (volumes > 32 MB), reserved 0x1, serial number 0xa4906b9d, unlabeled, FAT (16 bit)

In this output it is present the info FAT (16 bit), but it is not clear that the filesystem of the partition of the USB key is formatted vfat. If I execute the previous file -sL command on a USB key formatted by NTFS filesystem the output of the command is:

> file -sL /dev/sda
/dev/sda: DOS/MBR boot sector, code offset 0x52+2, OEM-ID "NTFS    ", sectors/cluster 8, Media descriptor 0xf8, sectors/track 63, heads 255, dos < 4.0 BootSector (0x0), FAT (1Y bit by descriptor); NTFS, sectors/track 63, physical drive 0x80, sectors 15654911, $MFT start cluster 786432, $MFTMirror start cluster 2, bytes/RecordSegment 2^(-1*246), clusters/index block 1, serial number 030fcd5a9fcd56a1c; contains bootstrap BOOTMGR

In this output is present the string NTFS, but is present also the string FAT, so with this output it is not easy to establish that the filesystem is vfat and not ntfs. ### The question ### Is there a command other than the previous ones that can provide the filesystem of an USB key before mounting it?