PID TTY      STAT   TIME COMMAND
 3476 pts/0    S      0:00 su ...
 3477 pts/0    S      0:02  _ bash
 8062 pts/0    T      1:16      _ emacs -nw ...
15733 pts/0    R+     0:00      _ ps xf
15237 ?        S      0:00 uwsgi ...
15293 ?        S      0:00  _ uwsgi ...
15294 ?        S      0:00  _ uwsgi ...

ps xf | sed '1d' | while read pid tty stat time command ; do [ -n "$(echo $command | egrep '^uwsgi')" ] && echo $pid ; done

$ ps hf -opid -C <process> | awk '{ print $1; exit }'

ps rf -opid,cmd -C <process-name> | awk '$2 !~ /^[|\]/ { print $1 }'

$ ps f -opid,cmd -Cchromium
  PID CMD
 2800 /usr/lib/chromium/chromium --type=zygote --enable-seccomp-sandbox
 2803  _ /usr/lib/chromium/chromium --type=zygote --enable-seccomp-sandbox
 2899      _ /usr/lib/chromium/chromium --type=renderer --enable-seccomp-sandbox --lang=en-US --force-fieldtrials=ConnCountImpact/conn_count_6/ConnnectB
 2906      |   _ /usr/lib/chromium/chromium --type=renderer --enable-seccomp-sandbox --lang=en-US --force-fieldtrials=ConnCountImpact/conn_count_6/Connn
 [  ... snip ... ]
 2861      _ /usr/lib/chromium/chromium --type=renderer --enable-seccomp-sandbox --lang=en-US --force-fieldtrials=ConnCountImpact/conn_count_6/ConnnectB
 2863          _ /usr/lib/chromium/chromium --type=renderer --enable-seccomp-sandbox --lang=en-US --force-fieldtrials=ConnCountImpact/conn_count_6/Connn
 2794 /usr/lib/chromium/chromium --enable-seccomp-sandbox --memory-model=low --purge-memory-button --disk-cache-dir=/tmp/chromium
 2796  _ /usr/lib/chromium/chromium --enable-seccomp-sandbox --memory-model=low --purge-memory-button --disk-cache-dir=/tmp/chromium
 3918  _ /usr/lib/chromium/chromium --type=gpu-process --channel=2794.45.1891443837 --gpu-vendor-id=0x10de --gpu-device-id=0x0611 --gpu-driver-version -
25308  _ [chromium] <defunct>
31932  _ /usr/lib/chromium/chromium --type=plugin --plugin-path=/usr/lib/mozilla/plugins/libflashplayer.so --lang=en-US --channel=2794.1330.1990362572


$ ps f -opid,cmd -Cchromium | awk '$2 !~ /^[|\]/ { print $1 }'
PID
2800
2794

$ # also supressing the header of ps (top line 'PID') -- add 'h' to ps
$ ps hf -opid,cmd -Cchromium | awk '$2 !~ /^[|\]/ { print $1 }'
2800
2794