Things can change while ps is running; the snapshot it gives is
only true for an instant, and might not be accurate by the time
it is displayed.
The args format specifier is allowed to produce a truncated
version of the command arguments. In some implementations, this
information is no longer available when the ps utility is
executed.
If the field width is too narrow to display a textual ID, the
system may use a numeric version. Normally, the system would be
expected to choose large enough field widths, but if a large
number of fields were selected to write, it might squeeze fields
to their minimum sizes to fit on one line. One way to ensure
adequate width for the textual IDs is to override the default
header for a field to make it larger than most or all user or
group names.
There is no special quoting mechanism for header text. The header
text is the rest of the argument. If multiple header changes are
needed, multiple -o options can be used, such as:
ps -o "user=User Name" -o pid=Process\ ID
On some implementations, especially multi-level secure systems,
ps may be severely restricted and produce information only about
child processes owned by the user.
