juodvalk@ee.eng.ohio-state.edu (Vincent Vladas Juodvalkis) (04/05/91)
I am trying to write a program in sh that will check a user's quota
before allowing them to use the compress tool. I have the program
writen and am now in the process of finding the thousand or so errors
that I always manage to code into a fifty line program.
Anyway, I am relatively new to shell programming and am having
dificulty with the cut tool. What I need to use it for is to get one
integer out of the output I get from the command "quota -v". The
output from this command is inconsistant between users so I cannot
just use the collumn feature of cut. The output from "quota -v" looks
like this...
Disk quotas for juodvalk (uid 2360):
Filesystem usage quota limit timeleft files quota limit timeleft
/tmp_mnt/homea
972 50000 50500 33 0 0
I use the line
`quota -v 2>&1 | grep -v quota | grep -v /`
to get
972 50000 50500 33 0 0
Now my problem comes when I try to cut this line. If I just try to
cut it by filed, trying to get the second field (50000), using the
following
quota -v 2>&1 | grep -v quota | grep -v / | cut -f2
the output I get is
972 50000 50500 33 0 0
Which is the same as before.
The reason that I came up with for this is that the generic delimeter
is a tab, and this seemed to imply that the spaces in the output were
not tabs. So I tried using spaces as the delimeter. The code I osed
looked like
quota -v 2>&1 | grep -v quota | grep -v / | cut -d" " -f2
the output I got was just a bank line. My hypothesis for this is that
the cut cuts after the first space it encounters and returns all that
ir finds until the next space it encounters (which in this case
happens to be the very next character, thus returning a line with
nothing in it).
What I need is either a was to get rid of all the extra spaces, or
maybe just a better way to cut up the lines.
I would appreciate any suggestion.
Vincent
-------------------------------------------------------------------------------
Vincent V. Juodvalkis "I can still move...
juodvalk@ee.eng.ohio-state.edu I can still drink."
juodvalk@cis.ohio-state.edu -Robert Reed
The Ohio State Universityhunt@dg-rtp.rtp.dg.com (Greg Hunt) (04/05/91)
In article <T2Q_XF#@ee.eng.ohio-state.edu>, juodvalk@ee.eng.ohio-state.edu (Vincent Vladas Juodvalkis) writes: > > ... > Now my problem comes when I try to cut this line. If I just try to > cut it by filed, trying to get the second field (50000), using the > following > > quota -v 2>&1 | grep -v quota | grep -v / | cut -f2 > > the output I get is > > 972 50000 50500 33 0 0 > > Which is the same as before. > > The reason that I came up with for this is that the generic delimeter > is a tab, and this seemed to imply that the spaces in the output were > not tabs. That's right. Cut's default delimiter is a tab, and that's part of the problem. But ... > So I tried using spaces as the delimeter. The code I osed > looked like > > quota -v 2>&1 | grep -v quota | grep -v / | cut -d" " -f2 > > the output I got was just a bank line. My hypothesis for this is that > the cut cuts after the first space it encounters and returns all that > ir finds until the next space it encounters (which in this case > happens to be the very next character, thus returning a line with > nothing in it). Yup. You figured it out right. > What I need is either a was to get rid of all the extra spaces, or > maybe just a better way to cut up the lines. > > I would appreciate any suggestion. I think it's time for you to learn about a more powerful tool for this sort of thing. Cut works great for simple cases, but when it gets to be a pain, I switch to using awk. Try using this command line: quota -v 2>&1 | <all the grep stuff> | awk '{print $2}' Awk ignores the multiple spaces, and this should print out 50000, which is what you're looking for. The $2 refers to the second field in the input line. You can do a lot more with awk than you can with cut, so when cut doesn't cut it (oooooh - that was a baaaaad one), try awk. The man page for awk (at least on my system) is pretty good, so take a look at it and see what else you can do with it. Enjoy! -- Greg Hunt Internet: hunt@dg-rtp.rtp.dg.com DG/UX Kernel Development UUCP: {world}!mcnc!rti!dg-rtp!hunt Data General Corporation Research Triangle Park, NC, USA These opinions are mine, not DG's.
curt@cynic.wimsey.bc.ca (Curt Sampson) (04/07/91)
In article <1991Apr5.144839.28412@dg-rtp.dg.com> hunt@dg-rtp.rtp.dg.com writes: > In article <T2Q_XF#@ee.eng.ohio-state.edu>, > juodvalk@ee.eng.ohio-state.edu (Vincent Vladas Juodvalkis) writes: > > > quota -v 2>&1 | grep -v quota | grep -v / | cut -d" " -f2 > > I think it's time for you to learn about a more powerful tool for > this sort of thing. Cut works great for simple cases, but when it > gets to be a pain, I switch to using awk. Try using this command > line: > > quota -v 2>&1 | <all the grep stuff> | awk '{print $2}' You can get awk to take care of all of the "grep stuff," too. In this case, he wanted to get the second field of the fourth line. Thus, you just have to tell awk to run its command on the fourth record (line) only: quota -v 2>&1 | awk 'NR == 4 { print $2 }' This is a faster and simpler way of doing it. You can also do the pattern matching with awk, if you like. Awk will do things like: quota -v 2>&1 | awk '$0 !~ /quota/ && $0 !~ /\// { print $2 }' to do the same search that the two grep commands did. I agree that awk is well worth learning. It easily doubles the power available from shell scripts, and is not terribly difficult. Anybody should be able to write simple awk programs in a couple of hours if they've got a decent book (or chapter) on it. cjs -- | "It is actually a feature of UUCP that the map of curt@cynic.uucp | all systems in the network is not known anywhere." curt@cynic.wimsey.bc.ca | --Berkeley Mail Reference Manual (Kurt Schoens)