mjhjmtu

I am new at scripting ... I can do very basic stuff, but now I need a hand.

I have a local filesystem that only will be mounted when I need to do a backup.

I'm starting with this.

#!/bin/bash
export MOUNT=/myfilesystem

if grep -qs $MOUNT /proc/mounts; then
 echo "It's mounted."
else
 echo "It's not mounted."; then
 mount $MOUNT;
fi

As I said, I'm very basic at scripting. I heard that you can check the status of the mount command by looking at the return codes.

RETURN CODES
 mount has the following return codes (the bits can be ORed):
 0 success
 1 incorrect invocation or permissions
 2 system error (out of memory, cannot fork, no more loop devices)
 4 internal mount bug
 8 user interrupt
 16 problems writing or locking /etc/mtab
 32 mount failure
 64 some mount succeeded

I don't know how to check that. Any guidance?

You can check the status code of mount, and most well written executables, with the shell special parameter ?.

From man bash:

? Expands to the exit status of the most recently executed foreground pipeline.

After you run the mount command, immediately executing echo $? will print the status code from the previous command.

# mount /dev/dvd1 /mnt
 mount: no medium found on /dev/sr0
# echo $?
 32

Not all executables have well defined status codes. At a minimum, it should exit with a success (0) or failure (1) code, but that's not always the case.

To expand on (and correct) your example script, I added a nested if construct for clarity. It's not the only way to test the status code and perform an action, but it's the easiest to read when learning.

#!/bin/bash
mount="/myfilesystem"

if grep -qs "$mount" /proc/mounts; then
 echo "It's mounted."
else
 echo "It's not mounted."
 mount "$mount"
 if [ $? -eq 0 ]; then
 echo "Mount success!"
 else
 echo "Something went wrong with the mount..."
 fi
fi

For more information on "Exit and Exit Status", you can refer to the Advanced Bash-Scripting Guide.

Many Linux distros have the mountpoint command. It can explicitly used to check if a directory is a mountpoint. Simple as this:

#!/bin/bash 
if mountpoint -q "$1"; then
 echo "$1 is a mountpoint"
else
 echo "$1 is not a mountpoint"
fi

The easiest way which doesn't require root is:

if $(df | grep -q /mnt/ramdisk); then

fi

or to see if it isn't mounted:

if ! $(df | grep -q /mnt/ramdisk); then

fi

One more way:

if [ "$(findmnt $mount_point)" ] ; then
 #Do something for positive result (exit 0)
else
 #Do something for negative result (exit 1)
fi

Short statements

Check if mounted:

mount|grep -q "/mnt/data" && echo "/mnt/data is mounted; I can follow my job!"

Check if not mounted:

mount|grep -q "/mnt/data" || echo "/mnt/data is not mounted I could probably mount it!"