Need a little help with grep syntax

okos · 01-25-2009, 11:22 PM

Hi

I am trying to print only a specific device using fdisk -l piped through grep. Specifically, I am looking to print only "/dev/sda1" However the entire line is printed including format and partition size. I want to cut off the rest of the line and only print the beginning of the line.

For example,
fdisk -l prints

Code:

Disk /dev/hdc: 60.0 GB, 60011642880 bytes
255 heads, 63 sectors/track, 7296 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Disk identifier: 0x02670266

   Device Boot      Start         End      Blocks   Id  System
/dev/hdc1   *           1        5840    46909768+  83  Linux
/dev/hdc2            5841        5948      867510   82  Linux swap
/dev/hdc3            5949        7296    10827810   83  Linux

Disk /dev/sda: 1000.2 GB, 1000204886016 bytes
255 heads, 63 sectors/track, 121601 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Disk identifier: 0x00073443

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1               1       11917    95723271    c  W95 FAT32 (LBA)
/dev/sda2           11918       37413   204796620   83  Linux
/dev/sda3           37414      108636   572098747+   f  W95 Ext'd (LBA)
/dev/sda5           37414       62909   204796588+   c  W95 FAT32 (LBA)
/dev/sda6           62910       75804   103579056    b  W95 FAT32

fdisk -l | grep Linux| grep -w '/dev/sd..' prints the entire line

Quote:

/dev/sda2 11918 37413 204796620 83 Linux

How would I cut off the rest of the line and print only /dev/sda2 ?

David the H. · 01-25-2009, 11:38 PM

Code:

fdisk -l | grep Linux| grep -o '/dev/sd..'

or

fdisk -l | grep Linux |cut -d " " -f 1

There may be even better ways to go about this. You could probably do the whole job with a single awk or perl command, for example.

okos · 01-25-2009, 11:50 PM

Quote:

Originally Posted by David the H.

Code:

fdisk -l | grep Linux| grep -o '/dev/sd..'

or

fdisk -l | grep Linux |cut -d " " -f 1

There may be even better ways to go about this. You could probably do the whole job with a single awk or perl command, for example.

The first one worked ! What does -o mean?

The second did not work. It printed

Code:

/dev/hdc1
/dev/hdc2
/dev/hdc3
/dev/sda2

EDIT
Never Mind about the question.
-o, --only-matching
Print only the matched (non-empty) parts of a matching line, with each such
part on a separate output line.