Shell Programming and Scripting

hi guys,

When for example, I want to get the size of a partition, I have done the following:

# result=`fdisk -l | grep /dev/sda1`
# echo $result
/dev/sda1 1 15000 120487468+ 83 Linux

and then I parse this output to get the size. That's just fine. The problem here is that, when I have a disk that does not have a good filesystem on it, it shows:

# result=`fdisk -l | grep /dev/sda1`
Disk /dev/hdd doesn't contain a valid partition table
#

I don't want to see that error message. I just want to turn it off. How can I do that?

By the way, I have tried redirecting to /dev/null, but no luck!

Thanks

Probably the fdisk utility sends the error message to fd2, the <stderr>. By using a pipeline you only redirect fd1, the <stdout> but leave <stderr> intact.

Probably this might work (i have changed the old-fashioned backticks, which shouldn't be used any more):

result=$(fdisk -l 2>/dev/null | grep /dev/sda1)

I hope this helps.

bakunin

Using $() instead of the 'old fashioned backticks' won't work on bourne though

How come they shouldn't be used anymore BTW (geniune question, not stirring like my first comment was )?

Alright! Thanks alot! it worked!

True, but AFAIK Bourne Shell is a bit outdated by now - this is what i meant by "oldfashioned". Its similar to using mono-character variable names in programs because FORTRAN/77 didn't honour more than 6 characters of an identifier. This might be, but nobody in his right mind would use a compiler which is more than 30 years old today.

In Korn-Shell, bash and most other modern shells the "$(...)" construct offers more flexibility and better readability (backticks are easily confused with single quotes as several threads here show) and better functionality. The reason why backticks are still working in these shells is not because the authors thought these were desirable but for backward compatibility. This is not a reason to still use them, even more so as the threadstarter seems to be learning shell scripting and should adopt proper practices as early as possible.

For an in-depth discussion about backticks see Barry Rosenbergs "Hands-On ksh93 Programming" or have a look here or take into account that backticks cannot be nested whereas "$(...)" can be, etc..

bakunin