Updated SC2009 (markdown)

SC2009.md

@@ -16,19 +16,24 @@ pgrep -f "$service" > /dev/null
 
 If you are just after a pid from a running program, then pgrep is a much safer alternative. Especially if you are also looking for a pid belonging to a certain user or group. All of the parameters are in one command and it can eliminate multiple greps, cuts, seds, awks, ect.
 
+If you want a field that's not the pid, consider doing this through `ps` + `pgrep` instead of `ps` + `grep`:
+
+```
+for pid in $(pgrep '^python$')
+do
+  user=$(ps -o user= -p "$pid")
+  echo "The process $pid is run by $user"
+done
+```
+
+This is more robust than `ps .. | grep python | cut ..` because it does not try to match against unrelated fields, such as if the user's name was `pythonguru`.
+
 ### Exceptions
 
-What if you have the pid and you are looking for the matching program name?
+You can [[ignore]] this error if you are trying to match against something that `pgrep` doesn't support:
 
-```sh
-pid=123; ps ax | grep "$pid"
 ```
-
-What if you want a range of the ps field, like from the 16th space to the end of the line?
-
-```sh
-ps ax | grep "$pid" | cut -d" " -f16-
+# pgrep does not support filtering by 'nice' value
+# shellcheck disable=SC2009
+ps -axo nice=,pid= | grep -v '^  0'
 ```
-
-Both are valid cases where SC2009 is not valid.
-