bash: differing newline count when assigning result to variable [duplicate]

Answer 1

Quoting Siegex:

Because the grep process itself is being returned by ps.

You can either of these:

"trick" grep to not match itself by surrounding one of the search characters in a character class [ ] which doesn't change the functionality:

Or, in this case,

Pipe to grep -v grep, so that the process doesn't match:

var=$(ps ax | grep -v grep | grep "$0")

---

See an example. Here we have a process sleep:

$ sleep 20 &
[1] 5602

If we check for it in the output of ps it appears twice!

$ ps -ef| grep sleep
me   5602  5433  0 09:49 pts/2    00:00:00 sleep 20
me   5607  5433  0 09:49 pts/2    00:00:00 grep --colour=auto sleep

So we can either use a character class:

$ ps -ef| grep [s]leep
me   5602  5433  0 09:49 pts/2    00:00:00 sleep 20

Or grep out the grep process:

$ ps -ef| grep sleep | grep -v grep
me   5602  5433  0 09:49 pts/2    00:00:00 sleep 20