check if directory exists using shell script

v333k · 04-20-2009, 05:57 PM

hi everyone,
I am trying to write some small script file that will check if a USB stick is connected to my pc or not. I can't seem to get it to work, but I am sure it is a very simple fix.

here is what I have in my file:

Code:

#!/bin/bash

usb_path = "/media/disk/"

if[ -f $usb_path ]
then
    echo "path exists"
else
    echo "path does not exist"
fi

I named my file as: check_usb.sh
and I changed permissions: chmod 755 check_usb.sh

The error I keep getting is this:
# ./check_usb
./check_usb.sh: line 3: usb_path: command not found
path exists

I am running on Fedora core 10.
Can anyone help me figure out what the problem is?

If I run these lines through console it works fine (meaning, I type the commands in this file straight in the command line/console).

thanks in advance.

GazL · 04-20-2009, 06:13 PM

It's the spaces around '='. Try

Code:

usb_path="/media/disk/"

also, you should have a space between your if and the '['.

Robhogg · 04-20-2009, 06:14 PM

Two small problems. Linux shell-scripts are very fussy about spacing in certain places:

Code:

usb_path = "/media/disk/"

There must not be any spaces around the assignment operator (=)

Code:

if[ -f $usb_path ]

There must be spaces around the square brackets.

This is really for the same reasons. A command is separated from its arguments by (a) space(s), so usb_path is seen as a command and not an assignment, while the [ ... ] construction is actually a command (it's equivalent to test ...) so needs the spaces.

Hope this helps,
Rob

v333k · 04-20-2009, 06:25 PM

PERFECT!

Thanks a lot!!!!

Robhogg · 04-20-2009, 07:27 PM

Another thought just occurred - if you're wanting to check that $usb_path exists, and it is a directory, you'd need:

Code:

if [ -d $usb_path ]

... as -f tests if something is a normal file (i.e. not a directory, block device, etc). If you just want to test that it exists (and don't care what sort of file it is), you could use:

Code:

if [ -e $usb_path ]

v333k · 04-21-2009, 09:59 AM

GREAT! Thanks for the tips!
At the moment, I want to check if the usb is connected to my PC - and I don't really care about other parts; therefore, it looks like using -e will be my best choice.

Thanks again!

Quote:

Originally Posted by Robhogg

Another thought just occurred - if you're wanting to check that $usb_path exists, and it is a directory, you'd need:

Code:

if [ -d $usb_path ]

... as -f tests if something is a normal file (i.e. not a directory, block device, etc). If you just want to test that it exists (and don't care what sort of file it is), you could use:

Code:

if [ -e $usb_path ]

jisjis · 04-23-2009, 06:31 AM

Quote:

Originally Posted by GazL

It's the spaces around '='. Try

Code:

usb_path="/media/disk/"

also, you should have a space between your if and the '['.

Linux is so finicky !!!

Linux

H_TeXMeX_H · 04-23-2009, 07:21 AM

Quote:

Originally Posted by jisjis

Linux is so finicky !!!

Ever tried C programming ?

v333k · 04-23-2009, 09:09 AM

Yes - actually, I am writing my socket server in C, but there are certain things that I would like to run in shell from a C program.
For example, it will be much faster (in my opinion) to obtain the directory list by running a shell script (ls -la) instead of writing a C function that will try to parse the directory, etc... etc... etc....

It is also nice to try something new and not go back to known methods of implementation!

Just a clarification - that wasn't me who said Linux is finiky!

In any case... thanks for your suggestion!

Libu · 04-23-2009, 09:29 AM

Quote:

Originally Posted by jisjis

Linux is so finicky !!!

Well its not linux, its bash and you can use perl if you want to

!