exec: correct and clarify example descriptions. (#3325)

pages/common/exec.md

@@ -6,14 +6,14 @@
 
 `exec {{command -with -flags}}`
 
-- Replace with the specified command using initialized environment variables:
+- Replace with the specified command, clearing environment variables:
 
 `exec -c {{command -with -flags}}`
 
-- Replace with the specified command and login to the default shell:
+- Replace with the specified command and login using the default shell:
 
 `exec -l {{command -with -flags}}`
 
-- Replace with the specified command and rename the process name:
+- Replace with the specified command and change the process name:
 
 `exec -a {{process_name}} {{command -with -flags}}`