Parse all column elements from a linux bash command output

Question

I would like to parse the column elements of the output from the command lsscsi.

Here is a sample output,

# lsscsi

[0:0:0:0]   disk   ATA   VBOX HARDDISK   1.0   /dev/sda
[0:0:1:0]   disk   ATA   VBOX HARDDISK   1.0   /dev/sdb
[1:0:1:0]   disk   ATA   VBOX HARDDISK   1.0   /dev/sdc

Example if I want column 2, my output should be,

disk
disk
disk

If cloumn 7,

/dev/sda
/dev/sdb
/dev/sdc

Thanks

anubhava · Accepted Answer · 2022-08-31 14:37:22Z

13

Use awk like this:

awk -v col=7 '{print $col}' file

Or to print 2 columns:

awk -v col1=2 -v col2=7 '{print $col1, $col2}' file

OR to make it print multiple columns using a colon delimited list:

awk -v col='2:7' '
BEGIN {n = split (col, arr, /:/)}
n {
   for (i=1; i in arr; ++i)
      printf "%s%s", $arr[i], (i < n ? OFS : ORS)
}' file

edited Aug 31, 2022 at 14:37

answered Dec 4, 2013 at 17:47

anubhava

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3 Comments

user2887201 Over a year ago

Thanks that works! out of curiosity, so what if i need both columns 2 & 7?

19wolf Over a year ago

Why not awk '{print $7}'?

anubhava Over a year ago

Sure, that can be done too. This is just passing column no from command line

Mindaugas Kubilius · Accepted Answer · 2013-12-04 18:33:04Z

6

With bash you can use 'read -a', this reads a line from standard input, splits using IFS field separator which has space by default and populates array variable which can be referenced as ${array[n]} (zero based).

while read -a arr; do
    echo "${arr[1]}"
    echo "${arr[6]}"
done

answered Dec 4, 2013 at 18:33

Mindaugas Kubilius

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2 Comments

sf8193 Over a year ago

what is arr in this case?

Mindaugas Kubilius Over a year ago

@sf8193 arr is an array variable which will hold input from stdin splitted by IFS

steviehs · Accepted Answer · 2017-10-19 18:40:19Z

2

Unfortunately lsscsi does not provide consistent parseable output nor the chance to change the field separator as far as I see. With two different harddisks on the same system the column for the device is differing by one! The following code sniplet should give you an idea about what I mean and how I worked around it... at least to get the device which is at the end of the line. To get the product name and the product revision correctly, it could also be an idea to call each device with lssci -c a:b:c:d and then parse this output.

lsscsi > /tmp/tmp$$.out
while read line
do
    echo $line
    echo 012345678901234567890123456789012345678901234567890123456789
    echo 0.........1.........2.........3.........4.........5.........
    ID=$(echo $line | cut -c2)
    TYPE=$(echo $line | cut -c16-18)
    PRODUCT=$(echo $line | sed -n 's/.\{18\}\(.*\) *\/dev\/.*/\1/p')
    DEVICE=$(echo $line | sed -n 's/.\{18\}.*\/dev\/\(.*\)/\1/p')
    echo $ID-$TYPE-$DEVICE-$PRODUCT
done

answered Oct 19, 2017 at 18:40

steviehs

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1 Comment

phuclv Over a year ago

would be easier to read if you use a different separator: 's#.\{18\}$.*$ */dev/.*#\1#p'

denten · Accepted Answer · 2015-12-03 04:03:09Z

1

Another easy way to do it without awk:

lsscsi | tr -s ' ' | cut -d' ' -f7

The last flag specifies the column.

edited Dec 3, 2015 at 4:03

answered Dec 2, 2015 at 16:23

denten

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4 Comments

MUY Belgium Over a year ago

fails : lsscsi has a fixed column width and visibly not field separator.

denten Over a year ago

Tested it again on a Linux machine and it works fine. My lsscsi output only has four columns, and therefore I use -f4 for the final argument. All output is treated as text in the shell, and in this case, we force separation by single space.

misinglink Over a year ago

this worked for me getting the 3rd column of docker image table in terminal

phuclv Over a year ago

it fails because the name field may contain spaces, and the path can also contain spaces although rarer

蔡宗容 · Accepted Answer · 2021-05-03 03:38:51Z

Simple examples:
(Each example is independent.)

Select the column 2:

echo -e "[0:0:0:0]   disk   ATA   VBOX HARDDISK   1.0   /dev/sda \
  \n[0:0:1:0]   disk   ATA   VBOX HARDDISK   1.0   /dev/sdb \
  \n[1:0:1:0]   disk   ATA   VBOX HARDDISK   1.0   /dev/sdc" \
  | awk '{print $2}'

Select the column 7:

echo -e "[0:0:0:0]   disk   ATA   VBOX HARDDISK   1.0   /dev/sda \
  \n[0:0:1:0]   disk   ATA   VBOX HARDDISK   1.0   /dev/sdb \
  \n[1:0:1:0]   disk   ATA   VBOX HARDDISK   1.0   /dev/sdc" \
  | awk '{print $7}'

Select the column 2 & 7:

echo -e "[0:0:0:0]   disk   ATA   VBOX HARDDISK   1.0   /dev/sda \
  \n[0:0:1:0]   disk   ATA   VBOX HARDDISK   1.0   /dev/sdb \
  \n[1:0:1:0]   disk   ATA   VBOX HARDDISK   1.0   /dev/sdc" \
  | awk '{print $2, $7}'

Results:

MUY Belgium · Accepted Answer · 2020-02-10 11:31:11Z

0

You may want to use the separation in columns with lsscsi : Use perl to insert tab and trim the fields.

lsscsi -g \
| perl -ne 'foreach$c(qw (64 53 47 30 21 13)){
              substr$_,$c,0,"\t"
            };
            s/ *([\t\n])/\1/g;  # trim the fields
            print'

Or one liner :

 lsscsi -g|perl -ne 'foreach$c(qw(64 53 47 30 21 13)){substr$_,$c,0,"\t"};s/ *([\t\n])/\1/g;print'

answered Feb 10, 2020 at 11:31

MUY Belgium

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