From the man page:

=$ man ps

     PS(1)                                                       PS(1)

     NAME
          ps, psu - process status

     SYNOPSIS
          ps [ -pa ]

          psu [ -pa ] [ user ]

 [snip]
          With the -p flag, ps also prints, after the system time, the
          baseline and current priorities of each process.

          The -a flag causes ps to print the arguments for the pro-
          cess.  Newlines in arguments will be translated to spaces
          for display.

plan9port's ps does not have a '-e' option, if given it is ignore.

Checking the script, ps uses the os version of ps  and the arguments -axww

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