ted@evi.com (Ted Stefanik) (05/03/91)
I've noticed that several Perl utilities scan "ps" output using splits and/or regular expressions. I'd like to add some cautions to these approaches. When a particular process's statistics numbers get too big for the column space alloted to that number, ps just slams the number into the preceeding column. For example, this looks nice: USER PID %CPU %MEM SZ RSS TT STAT TIME COMMAND ted 18374 51.2 3.0 488 380 p0 R 0:00 ps auxww If the process got memory hoggy and CPU hoggy, and was niced and not currently active, you'd get: USER PID %CPU %MEM SZ RSS TT STAT TIME COMMAND ted 18374 51.2 3.012488 1380 p0 IWN2345:45 ps auxww Notice that the size and time fields blend into the previous fields. In my opinion, splitting is out. You have to be very careful with regular expressions, because the white space is not always gauranteed to be there. I use substr, but that would also fail if the fields overflow one more place: USER PID %CPU %MEM SZ RSS TT STAT TIME COMMAND ted 18374 51.2 3.0124888 1380 p0 IWN12345:45 ps auxww (Although I both these are unlikely on my machine - 65MB swap space with weekly reboots.) ************************************************************************* * Ted Stefanik (Electronic Component Information Systems) * * Expert Views * * 100 Fifth Avenue ted@evi.com * * Waltham, MA 02154 ted%evi.com@uu.psi.com * * (617) 890-0333 uupsi!blt!ted * *************************************************************************
tchrist@convex.COM (Tom Christiansen) (05/04/91)
From the keyboard of ted@evi.com (Ted Stefanik):
:I've noticed that several Perl utilities scan "ps" output using splits
:and/or regular expressions. I'd like to add some cautions to these
:approaches.
:
:When a particular process's statistics numbers get too big for the column space
:alloted to that number, ps just slams the number into the preceeding column.
This is unfortunately pretty OS dependent. Some versions (mine, for
example) seems to guarantee a space between fields, even if some fields
should get wide.
USER PID %CPU %MEM SZ RSS TT STAT TIME COMMAND
tchrist 550 53.1 0.1 6508 464 o2 R 0:01 ps axu
user0 29596 0.0 12.6 65568 64300 q1 T N 10:34 program
user1 22172 52.4 31.2 278648 78840 pc VR N 100:14 another_program
The only thing here mildly difficult is finding all the STAT stuff, which
can contains blanks.
--tom
--
Tom Christiansen tchrist@convex.com convex!tchrist
"So much mail, so little time."