I need a little help with a #! /bin/sh script

[Gediminas2]

Hello,
I would like to know how to check if file exists (i need this part with my script)
I tried using google, but haven't found anything that would help.

here is the script I tried to write

#! /bin/sh
### By Gediminas
# 2007

# First USB port
echo "Mounting Device"
#if -f /dev/sda1
#then
 #if -d /media/usb
 #then echo "Already exist"
 #else sudo mkdir /media/usb
 #fi
sudo mount /dev/sda1 /media/usb
kdesu konqueror /media/usb
sudo umount /media/usb
# Second USB port
#elif -f /dev/sdb1
#then
 #if -d /media/usb
 #then echo "Already exist"
 #else sudo mkdir /media/usb
 #fi
sudo mount /dev/sdb1 /media/usb
kdesu konqueror /media/usb
sudo umount /media/usb
#else echo "Device not found"
#fi
exit

I commented the parts that were preventing int from running at all

This script should do the following:
when i plug in my USB device (MP3 player, or flash drive) the script checks if /dev/sda1 exists
if yes, it mounts it on /media/usb (if it exists, else creates this directory).
If /dev/sda1 doesn't exist then it should check if /dev/sdb1 exists and mount it on /media/usb .

now I don't know how to check that.
I tried using

if exist /dev/sda1

Like in DOS. It didn't work

if /dev/sda1

I thougt this might work

if /dev/sda1 =! 0

another bad idea

if -f /dev/sda1

i found this in google, but it doesn't work either.

Can anyone help me with this silly script?

[penguin.ch]

Re: I need a little help with a #! /bin/sh script

http://tldp.org/LDP/Bash-Beginners-G...ect_07_01.html

(as applicable to the Dash shell your script is actually referring to)

[Gediminas2]

Re: I need a little help with a #! /bin/sh script

http://tldp.org/LDP/Bash-Beginners-G...ect_07_01.html

(as applicable to the Dash shell your script is actually referring to)

Thanks, now I understand and my script works!

#! /bin/bash
### By Gediminas
# 2007

#check if /media/usb exists
echo "Cheking media ..."
if [ -d /media/usb ]
then echo "ok"
else sudo mkdir /media/usb
fi

# First USB port
echo "Mounting Device..."
if [ -b /dev/sda1 ]
then
sudo mount /dev/sda1 /media/usb
kdesu konqueror /media/usb
sudo umount /media/usb

# Second USB port
elif [ -b /dev/sdb1 ]
then
sudo mount /dev/sdb1 /media/usb
kdesu konqueror /media/usb
sudo umount /media/usb
else echo "Device not found"
fi
exit