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2. Short Tips

2.1 Handy Syslog Trick Paul Anderson, Tips-HOWTO maintainer

Edit your /etc/syslog.conf, and put in the following line:

# Dump everything on tty8
*.*                                     /dev/tty8

One caveat: REMEMBER TO USE TABS! syslog doesn't like spaces...

2.2 Script to view those compressed HOWTOs. Didier Juges, dj@destin.nfds.net

From a newbie to another, here is a short script that eases looking for and viewing howto documents. My howto's are in /usr/doc/faq/howto/ and are gzipped. The file names are XXX-HOWTO.gz, XXX being the subject. I created the following script called "howto" in the /usr/local/sbin directory:


#!/bin/sh
if [ "$1" = "" ]; then
    ls /usr/doc/faq/howto | less
else
    gunzip -c /usr/doc/faq/howto/$1-HOWTO.gz | less
fi


When called without argument, it displays a directory of the available howto's. Then when entered with the first part of the file name (before the hyphen) as an argument, it unzips (keeping the original intact) then displays the document.

For instance, to view the Serial-HOWTO.gz document, enter:

$ howto Serial

2.3 Is there enough free space??? Hans Zoebelein, zocki@goldfish.cube.net

Here comes a short script which will check from time to time that there is enough free space available on anything which shows up in mount (disks, cdrom, floppy...)

If space runs out, a message is printed every X seconds to the screen and 1 mail message per filled device is fired up.


#!/bin/sh

#
# $Id: check_hdspace,v 1.18 1996/12/11 22:33:29 root Exp root $
#

#
# Since I got mysterious error messages during compile when
# tmp files filled up my disks, I wrote this to get a warning
# before disks are full.
#
# If this stuff saved your servers from exploding,
# send praising email to zocki@goldfish.cube.net.
# If your site burns down because of this, sorry but I
# warned you: no comps.
# If you really know how to handle sed, please forgive me :)
#

#
# Shoot and forget: Put 'check_hdspace &' in rc.local.
# Checks for free space on devices every $SLEEPTIME sec.
# You even might check your floppies or tape drives. :)
# If free space is below $MINFREE (kb), it will echo a warning
# and send one mail for each triggering device to $MAIL_TO_ME.
# If there is more free space than trigger limit again,
# mail action is also armed again.
#

# TODO: Different $MINFREE for each device.
# Free /*tmp dirs securely from old junk stuff if no more free space.


DEVICES='/dev/sda2 /dev/sda8 /dev/sda9'         # device; your put disks here
MINFREE=20480                                   # kb; below this do warning
SLEEPTIME=10                                    # sec; sleep between checks
MAIL_TO_ME='root@localhost'                     # fool; to whom mail warning


# ------- no changes needed below this line (hopefully :) -------

MINMB=0
ISFREE=0
MAILED=""
let MINMB=$MINFREE/1024         # yep, we are strict :)

while [ 1 ]; do
        DF="`/bin/df`"
                for DEVICE in $DEVICES ; do
                ISFREE=`echo $DF | sed s#.\*$DEVICE" "\*[0-9]\*""\*[0-9]\*" "\*## | sed s#" ".\*##`
                
                if [ $ISFREE -le $MINFREE ] ; then
                        let ISMB=$ISFREE/1024
                        echo  "WARNING: $DEVICE only $ISMB mb free." >&2
                        #echo "more stuff here" >&2
                        echo -e "\a\a\a\a"
                        
                        if [ -z  "`echo $MAILED | grep -w $DEVICE`" ] ; then
                                echo "WARNING: $DEVICE only $ISMB mb free.      (Trigger is set to $MINMB mb)" \
                                | mail -s "WARNING: $DEVICE only $ISMB mb free!" $MAIL_TO_ME
                                MAILEDH="$MAILED $DEVICE"
                                MAILED=$MAILEDH
                                # put further action here like cleaning
                                # up */tmp dirs...
                        fi
                        elif [ -n  "`echo $MAILED | grep -w $DEVICE`" ] ; then
                                # Remove mailed marker if enough disk space
                                # again. So we are ready for new mailing action.
                                MAILEDH="`echo $MAILED  | sed s#$DEVICE##`"
                                MAILED=$MAILEDH
                        fi
                        
                done
                sleep $SLEEPTIME

done


2.4 Util to clean up your logfiles. Paul Anderson, Tips-HOWTO Maintainer>

If you're like me, you have a list with 430 subscribers, plus 100+ messages per day coming in over UUCP. Well, what's a hacker to do with these huge logs? Install chklogs, that's what. Chklogs is written by Emilio Grimaldo, grimaldo@panama.iaehv.nl, and the current version 1.8 available from ftp.iaehv.nl:/pub/users/grimaldo/chklogs-1.8.tar.gz. It's pretty self explanatory to install(you will, of course, check out the info in the doc subdirectory). Once you've got it installed, add a crontab entry like this:

# Run chklogs at 9:00PM daily.
00 21 * * *       /usr/local/sbin/chklogs -m

While you're at it, mention to the author how nice a peice of software this is:)

2.5 Handy Script to Clean Up Corefiles. Otto Hammersmith, ohammers@cu-online.com

Create a file called rmcores(the author calls it handle-cores) with the following in it:


#!/bin/sh
USAGE="$0 <directory> <message-file>"

if [ $# != 2 ] ; then
        echo $USAGE
        exit
fi

 echo Deleting...
find $1 -name core -atime 7 -print -type f -exec rm {} \;

echo e-mailing
for name in `find $1 -name core -exec ls -l {} \; | cut -c16-24`
do
        echo $name
        cat $2 | mail $name
done


And have a cron job run it every so often.

2.6 Moving directories between filesystems. Alan Cox, A.Cox@swansea.ac.uk

Quick way to move an entire tree of files from one disk to another

(cd /source/directory && tar cf - . ) | (cd /dest/directory && tar xvfp -)

[ Change from cd /source/directory; tar....etc. to prevent possibility of trashing directory in case of disaster. Thanks to Jim Dennis, jim@starshine.org, for letting me know. -Maint. ]

2.7 Finding out which directories are the largest. Mick Ghazey, mick@lowdown.com

Ever wondered which directories are the biggest on your computer? Here's how to find out.

du -S | sort -n

2.8 The Linux Gazette

Kudos go to John Fisk, creator of the Linux Gazette. This is an excellent e-zine plus, it's FREE!!! Now what more could you ask? Check it out at:

http://www.linuxgazette.com

BTW, It turns out that (1) LG is now out on a monthly basis, and (2) John Fisk no longer maintains it, the fellows at SSC do.

2.9 Pointer to patch for GNU Make 3.70 to change VPATH behavior. Ted Stern, stern@amath.washington.edu

I don't know if many people have this problem, but there is a "feature" of GNU make version 3.70 that I don't like. It is that VPATH acts funny if you give it an absolute pathname. There is an extremely solid patch that fixes this, which you can get from Paul D. Smith <psmith@wellfleet.com>. He also posts the documentation and patch after every revision of GNU make on the newsgroup "gnu.utils.bug" Generally, I apply this patch and recompile gmake on every system I have access to.

2.10 How do I stop my system from fscking on each reboot? Dale Lutz, dal@wimsey.com

Q: How do I stop e2fsck from checking my disk every time I boot up.

A: When you rebuild the kernel, the filesystem is marked as 'dirty' and so your disk will be checked with each boot. The fix is to run:

rdev -R /zImage 1

This fixes the kernel so that it is no longer convinced that the filesystem is dirty.

Note: If using lilo, then add read-only to your linux setup in your lilo config file (Usually /etc/lilo.conf)

2.11 How to avoid fscks caused by "device busy" at reboot time. Jon Tombs, jon@gtex02.us.es

If you often get device busy errors on shutdown that leave the filesystem in need of an fsck upon reboot, here is a simple fix:

To /etc/rc.d/init.d/halt or /etc/rc.d/rc.0, add the line

mount -o remount,ro /mount.dir

for all your mounted filesystems except /, before the call to umount -a. This means if, for some reason, shutdown fails to kill all processes and umount the disks they will still be clean on reboot. Saves a lot of time at reboot for me.

2.12 How to find the biggest files on your hard-drive.

Simon Amor, simon@foobar.co.uk

ls -l | sort +4n

Or, for those of you really scrunched for space this takes awhile but works great:

cd /
ls -lR | sort +4n

2.13 How to print pages with a margin for hole punching. Mike Dickey, mdickey@thorplus.lib.purdue.edu


        #!/bin/sh
        # /usr/local/bin/print
        # a simple formatted printout, to enable someone to
        # 3-hole punch the output and put it in a binder

        cat $1 | pr -t -o 5 -w 85 | lpr


2.14 A way to search through trees of files for a particular regular expression. Raul Deluth Miller, rockwell@nova.umd.edu

I call this script 'forall'. Use it like this:

forall /usr/include grep -i ioctl
forall /usr/man grep ioctl

Here's forall:

#!/bin/sh
if [ 1 = `expr 2 \> $#` ]
then
        echo Usage: $0 dir cmd [optargs]
        exit 1
fi
dir=$1
shift
find $dir -type f -print | xargs "$@"


2.15 A script for cleaning up after programs that create autosave and backup files. Barry Tolnas, tolnas@nestor.engr.utk.edu

Here is a simple two-liner which recursively descends a directory hierarchy removing emacs auto-save (#) and backup (~) files, .o files, and TeX .log files. It also compresses .tex files and README files. I call it 'squeeze' on my system.


#!/bin/sh
#SQUEEZE removes unnecessary files and compresses .tex and README files
#By Barry tolnas, tolnas@sun1.engr.utk.edu
#
echo squeezing $PWD
find  $PWD \( -name \*~ -or -name \*.o -or -name \*.log -or -name \*\#\) -exec
rm -f {} \;
find $PWD \( -name \*.tex -or -name \*README\* -or -name \*readme\* \) -exec gzip -9 {} \;


2.16 How to find out what process is eating the most memory. Simon Amor, simon@foobar.co.uk

ps -aux | sort +4n

-OR-
ps -aux | sort +5n

2.17 Rigging vi for C programming, Paul Anderson,Tips-HOWTO Maintainer

I do a lot of C programming in my spare time, and I've taken the time to rig vi to be C friendly. Here's my .exrc:


set autoindent
set shiftwidth=4
set backspace=2
set ruler


What does this do? autoindent causes vi to automatically indent each line following the first one indented, shiftwidth sets the distance of ^T to 4 spaces, backspace sets the backspace mode, and ruler makes it display the line number. Remember, to go to a specific line number, say 20, use:


vi +20 myfile.c


2.18 Using ctags to ease programming.

Most hackers already have ctags on their computers, but don't use it. It can be very handy for editing specific functions. Suppose you have a function, in one of many source files in a directory for a program you're writing, and you want to edit this function for updates. We'll call this function foo(). You don't where it is in the source file, either. This is where ctags comes in handy. When run, ctags produces a file named tags in the current dir, which is a listing of all the functions, which files they're in and where they are in said files. The tags file looks like this:



ActiveIconManager       iconmgr.c       /^void ActiveIconManager(active)$/
AddDefaultBindings      add_window.c    /^AddDefaultBindings ()$/
AddEndResize    resize.c        /^AddEndResize(tmp_win)$/
AddFuncButton   menus.c /^Bool AddFuncButton (num, cont, mods, func, menu, item)$/
AddFuncKey      menus.c /^Bool AddFuncKey (name, cont, mods, func, menu, win_name, action)$/
AddIconManager  iconmgr.c       /^WList *AddIconManager(tmp_win)$/
AddIconRegion   icons.c /^AddIconRegion(geom, grav1, grav2, stepx, stepy)$/
AddStartResize  resize.c        /^AddStartResize(tmp_win, x, y, w, h)$/
AddToClientsList        workmgr.c       /^void AddToClientsList (workspace, client)$/
AddToList       list.c  /^AddToList(list_head, name, ptr)$/


To edit, say AddEndResize() in vim, run:

vim -t AddEndResize

This will bring the appropriate file up in the editor, with the cursor located at the beginning of the function.

2.19 Why does sendmail hang for 5 minutes on startup with RedHat? Paul Anderson, paul@geeky1.ebtech.net

This is a fairly common problem, almost to the point of being a FAQ. I don't know if RedHat has fixed this bug in their distribution, but you can repair it yourself. If you look in your /etc/hosts file, you will find it looks something like:

127.0.0.1               localhost       yourbox

When sendmail starts, it does a lookup on your hostname(in this example, yourbox). It then finds that the IP for yourbox is 127.0.0.1, sendmail doesn't like this, so it does the lookup again. It continues with this for a while until it eventually gives up and exits. Fixing the problem is extremely easy, edit your /etc/hosts file and change it to something like this:

127.0.0.1               localhost
10.56.142.1             yourbox

2.20 How do I configure RedHat for using color-ls? Paul Anderson, paul@geeky1.ebtech.net

RedHat's distribution comes with color-ls, however why they don't configure it for colour use by default is beyond me. Here's to fix it.

First, type eval `DIRCOLORS`

Next, alias ls='ls --color=auto'

And put the 'alias.....' in your /etc/bashrc

2.21 How do I find which library in /usr/lib holds a certain function? Pawel Veselow, vps@unicorn.niimm.spb.su

What if you're compiling and you've missed a library that needed linking in? All gcc reports are function names... Here's a simple command that'll find what you're looking for:

for i in *; do echo $i:;nm $i|grep tgetnum 2>/dev/null;done

Where tgetnum is the name of the function you're looking for.

2.22 I compiled a small test program in C, but when I run it, I get no output!

You probably compiled the program into a binary named test, didn't you? Linux has a program called test, which tests if a certain condition is true, it never produces any output on the screen. Instead of just typing test, try: ./test


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