Bash script to output path to USB flash memory stick

Question

How would I return (output) the path to any USB flash memory stick(s) connected to the local computer using bash (Ubuntu and Linux Mint)?

Background:

I'm providing users with an automated backup script. (The actual backup software is already installed on their computer.)

The user's job is to plug in a USB flash memory stick and enter one command at the terminal (without any parameters, options or any other variable information).

I need a bash script that can find the path to the USB flash memory stick. If more than one such path is found, I will probably just abort and pop up a message to contact me. Rather than make a complicated script, it is easier for me to just tell them to make sure only one memory stick is plugged into the computer at the time they wish to perform a backup.

Answer 1

After plugging in a USB device you can tell what was installed by simply looking at this path:

$ ls -l /dev/disk/by-id/usb*

Example

$ ls -l /dev/disk/by-id/usb*
lrwxrwxrwx. 1 root root  9 Mar 12 01:01 /dev/disk/by-id/usb-JMTek_USBDrive-0:0 -> ../../sdb
lrwxrwxrwx. 1 root root 10 Mar 12 01:01 /dev/disk/by-id/usb-JMTek_USBDrive-0:0-part1 -> ../../sdb1

With the above information your script could simply look at those entries using something like readlink:

$ readlink -f /dev/disk/by-id/usb-JMTek_USBDrive-0:0*
/dev/sdb
/dev/sdb1

And then using the mount command walk backwards to find out what directory the device was automounted under:

$ mount | grep '/dev/sdb\b'
$ mount | grep '/dev/sdb1\b'
/dev/sdb1 on /run/media/saml/HOLA type vfat (rw,nosuid,nodev,relatime,uid=1000,gid=1000,fmask=0022,dmask=0077,codepage=437,iocharset=ascii,shortname=mixed,showexec,utf8,flush,errors=remount-ro,uhelper=udisks2)

This could be expanded to a one liner like this:

$ readlink -f /dev/disk/by-id/usb-JMTek_USBDrive-0:0* | \
    while read dev;do mount | grep "$dev\b" | awk '{print $3}';done
/run/media/saml/HOLA

Getting a device's ID

You can parse this out like so from the output from /dev/disk/by-id/usb*, like so:

$ ls /dev/disk/by-id/usb* | sed 's/.*usb-\(.*\)-[0-9]:.*/\1/'
JMTek_USBDrive
JMTek_USBDrive

Incidentally this information is a concatenation of the USB's manufacturer + product descriptions.

$ usb-devices
...
T:  Bus=02 Lev=02 Prnt=02 Port=01 Cnt=02 Dev#= 10 Spd=12  MxCh= 0
D:  Ver= 1.10 Cls=00(>ifc ) Sub=00 Prot=00 MxPS= 8 #Cfgs=  1
P:  Vendor=058f ProdID=9380 Rev=01.00
S:  Manufacturer=JMTek
S:  Product=USBDrive
C:  #Ifs= 1 Cfg#= 1 Atr=80 MxPwr=100mA
I:  If#= 0 Alt= 0 #EPs= 2 Cls=08(stor.) Sub=06 Prot=50 Driver=usb-storage
...

You can also access it this way once you've established which device (/dev/sd*) the USB device is using, through UDEV:

$ udevadm info --query=all --name=sdb | grep -E "MODEL=|VENDOR=|ID_SERIAL"
E: ID_MODEL=USBDrive
E: ID_SERIAL=JMTek_USBDrive-0:0
E: ID_VENDOR=JMTek

Answer 2

You can write a script to go through /etc/mtab and look at mounted devices, then use udevadm to check whether they're USB devices. /etc/mtab includes both the name of the device in /dev and its mount point. So you could do something like:

IFS=$'\n'
for mtabline in `cat /etc/mtab`; do 
  device=`echo $mtabline | cut -f 1 -d ' '`
  udevline=`udevadm info -q path -n $device 2>&1 |grep usb` 
  if [ $? == 0 ] ; then
    devpath=`echo $mtabline | cut -f 2 -d ' '`
    echo "devpath: $devpath"
  fi
done

(You need to set IFS in your script so that mtab is read line by line, rather than "word" by "word").

Answer 3

On my desktop with no usb flash devices present:

% lsblk -o tran,name,mountpoint
> TRAN   NAME   MOUNTPOINT
> sata   sda
>        ├─sda1 /esp
>        ├─sda2 /
>        ├─sda3 /mnt/sda3
>        ├─sda4
>        └─sda5
> sata   sdb
> sata   sdc
> sata   sr0

On my laptop with two:

% lsblk -o tran,name,mountpoint
> TRAN   NAME   MOUNTPOINT
> usb    sda
>        ├─sda1 /esp
>        └─sda2 /
> usb    sdb
>        └─sdb1 /home
> sata   sr0

That should be all you need.

So some others also told me that some debian family systems do not yet support the transport option. In that case, try this:

    ( set -- $(lsblk -ndo name,rm)
        while [ $# -ge 2 ] ; do {
            [ $2 -eq 1 ] && \
                udevadm info --query=all --name "/dev/$1"
        shift 2 
     } ; done )   

The above command first queries lsblk for a list of current (parent-only - so only sda and not sda1) block devices by name and a column for the removable flag. The output looks like:

sda 0
sdb 1
sdc 1

Only the devices flagged with 1 are removable.

So we set our ( subshell's ) positional parameters to the split content which makes two parameters per entry. while we have at least 2 positional parameters we[ test ] $2 for the 1 removable flag, && and if present we query udevadm the system's device manager for all information it has on our first positional parameter, or /dev/$1. Next shift our first 2 positional parameters away and start over with the next two.

udevadm provides a lot of info on devices you might be interested in, but if you also really just want to get straight to the point, you could add the following |pipe to udevadm's stdout:

    udevadm info --name "/dev/$1" |\
        grep -q ID_BUS=usb && echo "/dev/$1"

This much would provide you a list of only parent /dev/$DEV removable usb block devices currently present in the system in the format:

/dev/$DEV /dev/$ALSODEV

If at this point you were interested only in mount points of mounted partitions of the above provided parent links you could roll it all together with findmnt like this:

( set -- $(lsblk -ndo name,rm)
    while [ $# -ge 2 ] ; do {
        [ $2 -eq 1 ] &&
            udevadm info --query=all --name "/dev/$1" |\
            grep -q ID_BUS=usb &&
                 printf 'findmnt %s -no TARGET ;' "/dev/$1" /dev/"$1"[0-9]
        shift 2 ; } ; done ) |\ 
    . /dev/stdin

This should provide you a list like:

/removable/usb/device/mount/point/1
/ditto/2
/also/3

Answer 4

Here's the approach I'm using. It comes from:

https://unix.stackexchange.com/a/119782/15010
https://unix.stackexchange.com/a/60335/15010

export USBKEYS=($(
    for blk in $(lsblk -ndo name) ; do {
        udevadm info --query=all --name "/dev/$blk" |\
        grep -q ID_BUS=usb &&
            printf 'findmnt %s -no TARGET ;'\
                "/dev/$blk" /dev/"$blk"[0-9]
        } ; done 2>&- |. /dev/stdin 
))
echo "$USBKEYS"
export STICK
case ${#USBKEYS[@]} in
    0 ) echo "No USB stick found."; exit 0 ;;
    1 ) STICK=$USBKEYS; echo "STICK=$USBKEYS" ;;
    * ) NOTE: the code for this case is not included in the interest of brevity.
esac

This is also working for me. It mostly comes from https://unix.stackexchange.com/a/119260/15010

#!/bin/bash

while read mtabline
do
  device=`echo $mtabline | awk '{print $1}'`
  udevline=`udevadm info -q path -n $device 2>&1 |grep usb` 
  if [ $? == 0 ] ; then
    echo "$device"
  fi
done < /etc/mtab