Parsing functionality in shell script

Question

If I am trying to look up which host bus is the hard drive attached to, I would use

ls -ld /sys/block/sd*/device

it returns

lrwxrwxrwx 1 root root 0 Oct 18 14:52 /sys/block/sda/device -> ../../../1:0:0:0

Now if I want to parse out that "1" in the end of the above string, what would be the quickest way?

Sorry I am very new to shell scripting, I can't make full use of this powerful scripting language.

Thanks!

Birei · Accepted Answer · 2013-10-18 22:13:18Z

2

Split with slashes, select last field, split it with colons and select first result:

ls -ld /sys/block/sd*/device | awk -F'/' '{ split( $NF, arr, /:/ ); print arr[1] }'

It yields:

answered Oct 18, 2013 at 22:13

Birei

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2 Comments

return 0 Over a year ago

can you explain "{ split( $NF, arr, /:/ ); print arr[1] }"?

Birei Over a year ago

Yes. It's very simple. $NF is the last field (1:0:0:0) and arr is an array variable where it saves each part split, so I access to the first one.

Gilles Quénot · Accepted Answer · 2013-10-18 22:24:33Z

1

Try doing this :

$ ls -ld /sys/block/sd*/device |  grep -oP '\d+(?=:\d+:\d:\d+)'
0
2
3

or

$ printf '%s\n' /sys/block/sd*/device |
    xargs readlink -f |
    grep -oP '\d+(?=:\d+:\d:\d+)'

and if you want only the first occurence :

grep ...-m1 ...

edited Oct 18, 2013 at 22:24

answered Oct 18, 2013 at 22:18

Gilles Quénot

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