Linux/Cut set f2 in place of f1 if f1 is empty

Question

i have the following problem at work:

we have a xml file from which we read infos like hostname, address and os via xmlstarlet and redirect them into a separate file.

this is the Script:

xmlstarlet sel -t -m "//host" -m "hostnames/hostname" -v "@name" -b -o "|" -v "address[@addrtype='ipv4']/@addr" -o "|" -v "os/osmatch[1]/@name" -n nmap.xml > newfile

now we have 3 infos each line separated by a | like

imahost|192.168.50.6|windows

some servers do not have a hostname but only the ip and the os like

|192.168.50.7|windows

then we cut the hostname and the ip out from the file where f1 is hostname and f2 is ip like:

cat newfile | cut -d"|" -f1,2

it looks like this

imahost|192.168.50.6
|192.168.50.7
...

if a hostname is not available as in the second line the ip should be inserted in the first position like

imahost|192.168.50.6
192.168.50.7|192.168.50.7
...

how do we do this? ^^

i thank you in advance for every helpful answer

Answer 1

awk can handle empty columns:

awk 'BEGIN{FS=OFS="|"} $1==""{$1=$2} {print $1,$2}' file

Set input and output field separator to |. If first column is empty copy content of second column to first column. In any case print first and second row.

Output:

imahost|192.168.50.6
192.168.50.7|192.168.50.7

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See: 8 Powerful Awk Built-in Variables – FS, OFS, RS, ORS, NR, NF, FILENAME, FNR