I’m scripting something in Bash for Linux systems. How would I check a disk for partitions in a robust manner?
I could use grep, awk, or sed to parse the output from fdisk, sfdisk, etc., but this doesn’t seem to be an exact science.
I could also check if there are partitions in /dev, but it is also possible that the partitions exist and haven’t been probed yet (via partprobe, as an example).
What would you recommend?
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Answer
I think I figured out a reliable way. I accidentally learned some more features of partprobe while reading the man page:
-d Don’t update the kernel. -s Show a summary of devices and their partitions.
Used together, I can scan a disk for partitions without updating the kernel and get a reliable output to parse. It’s still parsing text, but at least the output isn’t as “human-oriented” as fdisk or sfdisk. This also is information as read from the disk and doesn’t rely on the kernel being up-to-date on the partition status for this disk.
Take a look:
On a disk with no partition table:
# partprobe -d -s /dev/sdb (no output)
On a disk with a partition table but no partitions:
# partprobe -d -s /dev/sdb /dev/sdb: msdos partitions
On a disk with a partition table and one partition:
# partprobe -d -s /dev/sdb /dev/sdb: msdos partitions 1
On a disk with a partition table and multiple partitions:
# partprobe -d -s /dev/sda /dev/sda: msdos partitions 1 2 3 4 <5 6 7>
It is important to note that every exit status was 0 regardless of an existing partition table or partitions. In addition, I also noticed that the options cannot be grouped together (partprobe -d -s /dev/sdb works while partprobe -ds /dev/sdb does not).