Extract a column from whitespace-separated fields that are not aligned

Question

How can we extract a column from output in which whitespace is not in a regular format?

For example, when we type ps -ef, it shows all the process, process id's.... etc. How can we get only the last column or any specific column?

Answer 1

Using -o option you can specify what fields should be displayed. List of available fields you can find in man ps or using ps L.

For example using ps -eo user,command will display usernames and commands - something like this:

root /bin/login --
root /sbin/getty 

You can also use -O and parameters which will cause using some default fields and appending that specified by you, but if you want to parse output I will recommend o.

Answer 2

Maybe you want:

ps -eo comm

To get the command name or

ps -eo args

To get the command args or

ps -eo args="Last-Arg" | awk '{print $NF}'

To get the last argument.