How to always cut the PID from `ps aux` command?

You can always use pgrep to get process's PID

E.g PIDs with PS AUX

wix@wsys:~$ ps aux | grep sshd
root      1101  0.0  0.0  72304  3188 ?        Ss   Oct14   0:00 /usr/sbin/sshd -D
root      6372  0.0  0.1 105692  7064 ?        Ss   06:01   0:00 sshd: wix [priv]
wix       6481  0.0  0.1 107988  5748 ?        S    06:01   0:00 sshd: wix@pts/1
root      6497  0.0  0.1 105692  7092 ?        Ss   06:01   0:00 sshd: wix [priv]
wix       6580  0.0  0.1 107988  5484 ?        S    06:01   0:00 sshd: wix@pts/2
wix       6726  0.0  0.0  13136  1044 pts/1    S+   06:12   0:00 grep --color=auto sshd

Now just pgrep to get PIDs

wix@wsys:~$ pgrep sshd
1101
6372
6481
6497
6580
wix@wsys:~$ 

You can use the option -o to print only the pid:

ps -u user -o pid

-d ' ' means using a single space as delimiter. Since there're 1 space before 2049 and 2 spaces before 12290, your command get them by -f 2 and -f 3.

I recommend using ps aux | awk '{print $2}' to get those pids.

Or you can use tr to squeeze those spaces first ps aux | tr -s ' ' | cut -d ' ' -f 2