Проблема с pgrep

       -x, --exact
              Only match processes whose names (or command lines if -f is specified) exactly match the pattern.

pgrep -f "([^\s]+/)?notification-daemon"
1107
5338

pgrep -f "([\S]+/)?$notification-daemon\b"
1101
1105
1107
1137
4002
4010
4131
4414
4535
4701
5338

ps aux |grep notification-daemon
earlyoom    1107  0.0  0.0   2612   880 ?        SLs  10:34   0:00 /usr/bin/earlyoom -r 0 -m 60 -s 100 --avoid (^|/)(init|X|sshd|firefox|firefox-bin|dockerd|docker-proxy|gpg-agent|gpg2|whisper|pulseaudio|dwm|monitoring.py|redshift|kbdd|notification-daemon|numlockx|unclutter|autocutsel)$
user        5338  0.0  0.0 262948 24168 ?        Sl   10:34   0:00 /usr/lib/notification-daemon/notification-daemon
user      224915  0.0  0.0   6476  2280 pts/5    S+   13:51   0:00 grep --color=always --no-messages notification-daemon

ps axo pid,comm | perl -ln -e "print for /^\s+(\d+)\s+$TARGET$/"

man grep

        -P, --perl-regexp

ps axo pid,comm | grep -P "^\s+\d+\s+$TARGET$" | awk '{print $1}'

grep notification-daemon /proc/+([[:alnum:]])/comm 2>&1 | grep -v self | cut -d/ -f3 | xargs kill -9

SYNOPSIS
pgrep [options] pattern

OPERANDS
       pattern
              Specifies an Extended Regular Expression for matching against the process
              names or command lines.