bash replace part of command's output based on another command's output

Question

I have 2 commands that output the devices on my linux system:

$ devlist -t csv -o device,vol_name
device,vol name,
/dev/mapper/mpath62,volume1,
/dev/mapper/mpath63,my_volume,
/dev/mapper/mpath64,foo,
/dev/mapper/mpath65,bar,
/dev/mapper/mpath66,2nd_vol,
$ multipathd -k'show maps'
name     sysfs uuid             
mpath62  dm-0  20017380029ab0043
mpath65  dm-1  20017380029ab0044
mpath66  dm-2  20017380029ab0045
mpath63  dm-3  20017380029ab0046
mpath64  dm-4  20017380029ab0047

How can I merge the output to print (preferably, w/o creating temporary files):

device,vol name,
/dev/dm-0,volume1,
/dev/dm-3,my_volume,
/dev/dm-4,foo,
/dev/dm-1,bar,
/dev/dm-2,2nd_vol,

Thanks

anubhava · Accepted Answer · 2015-03-05 15:22:15Z

1

You can use awk with process substitution:

awk -F '[/, ]+' 'FNR==NR{a[$1]=$2; next}
   FNR==1{print;next}
   $4 in a{printf "/%s/%s,%s,\n", $2, a[$4], $(NF-1)}
' <(multipathd -k'show maps') <(devlist -t csv -o device)
device,vol name,
/dev/dm-0,volume1,
/dev/dm-3,my_volume,
/dev/dm-4,foo,
/dev/dm-1,bar,
/dev/dm-2,2nd_vol,

edited Mar 5, 2015 at 15:22

answered Mar 5, 2015 at 14:59

anubhava

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5 Comments

Maxim_united Over a year ago

It only prints the first field for me (w/o the volume1, my_volume, etc...). How can I print any extra fields if there are in the original output?

anubhava Over a year ago

Since I don't have these command available, I could only test with the output provided and that is giving the shown output. Are you getting exact same output as shown? Try: awk -F '[/,[:blank:]]+' at the start.

Maxim_united Over a year ago

You're right. I accidently omitted a comma after the second field. Updated original post.

Maxim_united Over a year ago

Works! Thanks! How can I print any additional fields if I choose to add to the devlist command?

anubhava Over a year ago

All the fields from devlist commands are available from $2 onwards. You can just add few more fields in printf above.

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