How to capture column from command output and convert it to a row

Capture column from command output and convert it to a row to pass it further.

The simplest usage scenario is to convert single column output to TAB separated row.

$ pgrep dnsmasq | paste -s

2430    2431

This solution does not play well with ps output as you get redundant space characters because data is aligned using those.

$ ps -opid= -u netdata | paste -s

1943    1985   24046   24137

You can remove all space characters and keep values separated using TAB.

$ ps -opid= -u netdata | paste -s | tr -d ' '

1943    1985    24046   24137

Alternatively, you can squeeze space characters, ignore these at the beginning of the row, and use remaining space characters to keep values separated.

$ ps -opid= -u netdata | paste -s -d " " | tr -s ' ' | sed 's.^ *..'

1943 1985 24046 24137

It gets slightly more complicated when you want to extract a specific column.

$ ps ax --no-header | grep -v grep | grep sshguard | tr -s " " | sed "s.^ *.." | cut -d " " -f1 | paste -s -d ' '
1394 1449

There is an alternative, of course. Use awk to print specific column using custom output record separator (ORS built-in variable).

$ ps ax --no-header |  awk  -v ORS=" " '/firefox/ {print $1} END{printf "\n"}' 

3867 3947 4058 4352 4604 4688 22346