Unix and Linux Tips: Juni 2010

Rabu, 30 Juni 2010

Unix Tip: BOURNE SHELL PSEUDO HASH TABLES

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UNIX GURU UNIVERSE
UNIX HOT TIP

Unix Tip 3067 - June 30, 2010

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BOURNE SHELL PSEUDO HASH TABLES

The best way to explain this
is with an example:

You may want to write a simple
script that launches an xterm
window with different color
options. Pseudo hash tables in
bourne shell.

$ xwindow MidnightBlue

An easy way to this is by first
listing the supported colors in
the script (pseudo hash table):

DarkSlateGrey="#2f4f4f"
DimGrey="#696969"
MidnightBlue="#191970"
NavyBlue="#000080"

Next, simply grab the hex color
code by using the following
command:

BGColor=`eval echo $"$(echo $1)"`

"$(echo $1)" evaluates to "MidnightBlue" and
`eval echo $MidnightBlue evaluates to "#191970".

Simply launch the xterm window
using $BGColor as the background
color:

xterm -bg="$BGColor" &

This method for extracting pseudo hash
values may be used for NIS map files,
file date stamps, GUI colors, etc.

This tip generously supported by: Jasper.Silvis@PHL.Boeing.com

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Selasa, 29 Juni 2010

Unix Tip: BE A GURU - RTFM

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Unix Tip 3066 - June 29, 2010

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BE A GURU - RTFM

The best way, is to learn
to be the best Unix Guru is
take the time to RTFM. Do
not always depend on someone
else to be there with the
knowledge.

DON'T BE LAZY!

By the Way, for those that
don't know by now.

RTFM = READ THE F^CKING MANUAL

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Senin, 28 Juni 2010

Unix Tip: ONE STEP AT A TIME WITH !!

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UNIX HOT TIP

Unix Tip 3065 - June 28, 2010

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ONE STEP AT A TIME WITH !!

For example using C shell I want
to edit a handful of files that
contain the string "ProcessInput"
in my current directory.

Step 1:
Find the files which uses "ProcessInput"

% grep "ProcessInput" *.c
a.c:ProcessInput ( int a )
b.c:Description : ProcessInput is used to process the input
given by the user
b.c:Call ProcessInput to perform ...
c.c:val = ProcessInput(2) ;
c.c:val = ProcessInput(3) ;

Step 2:
Extract the filenames on the left.
$!! | awk -F: '{print $1}'
a.c
b.c
b.c
c.c
c.c

step 3:
Remove the duplicates
!! | sort -u

Step 4:
Now edit it !
vi `!!`

which runs vi `grep "ProcessInput" *.c | awk -F: '{print $1}'
| sort -u`

This tip generously supported by: desikann@future.futsoft.com

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Minggu, 27 Juni 2010

Unix Tip: PRINTING WITH NO SPACE

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Unix Tip 3064 - June 27, 2010

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PRINTING WITH NO SPACE

Sometimes there isn't enough space
in the spooling directory to print
a large file. This isn't the case
so much anymore since disk drives
are so large now.

If the file fills up the spooling
directory use and you are using
BSD "lpr" then you can pass it
the -s option.

This will create a symlink to the
file instead of coping it.

"lp" creates a symlink by default.
You can use the -c options to
force it to copy the file instead,
if needed.

Some flavors differ, check yours.

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Sabtu, 26 Juni 2010

Unix Tip: To grab all hidden files

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Unix Tip 3063 - June 26, 2010

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To grab all hidden files

A safe way of grabbing all "hidden"
files is to use '.??*' rather than
'.*' since this will only match 3
or more characters. Admittedly,
this will miss any hidden files
that are only a single character
after the ., but it will always
miss '.' & '..', which is probably
more important...

We can use .[a-zA-Z0-9]* to grab
all hidden files other
than . and .. we will not get
hidden files which dont have any
alphanumeric character following
the first '.' - can someone tell
how to go about this

This tip generously supported by: muraliaj@synopsys.com

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Sabtu, 19 Juni 2010

Unix Tip: GETTING RID OF ^M

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Unix Tip 3056 - June 19, 2010

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GETTING RID OF ^M

How to get rid of ^M
in text files .

tr -d '^M' <inputfile >outputfile

But how to get this
'^M' in the command
line:

Keep CTRL pressed
and then press v and m

This tip generously supported by: sojan@psidata.com

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Jumat, 18 Juni 2010

Unix Tip: REMOVE JUST THE FILES

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Unix Tip 3055 - June 18, 2010

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REMOVE JUST THE FILES

To removal only the files
(not subdirectories) in
the current directory, use
the following command:

rm `ls -l | grep -v '^d' | awk '{ print $9 }'`

This tip generously supported by: rrs@assc.com.ve

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Kamis, 17 Juni 2010

Unix Tip: SOLARIS CHANGING SEASONS

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Unix Tip 3054 - June 17, 2010

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SOLARIS CHANGING SEASONS

During a session, sometimes
we have a need to change the
system time for our session
only. We have used it to
simulate time based testing.

export TZ=ESThhEDT

The EST set your time to Eastern
Standard Time and EDT is Eastern
Daylight Time.

hh is the number of hours you
wish to change.

Example: Currently the system
date is Tue Jun 19 13:38:03 EDT 2001

and you wish to set it to
yesterday at the same time.
You would substitute a positive
29 for hh.

export TZ=EST29EDT

Now the shell time is:
Mon Jun 18 13:38:50 EDT 2001

WHY 29 and not 24? The main
UNIX clock is set from GMT not
EST therefore you have to add
5 hours to your backward
calculations to get the same
exact time since EST is
GMT - 5 hours.

Use negitive numbers to set
the clock into the future.

Also if you need to set the
minutes and seconds it is
hh:mm:ss. These are all the
number of hours, minutes and
seconds from GMT that you wish
to set.

This is for Solaris 2.6, your
mileage may vary.

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Rabu, 16 Juni 2010

Unix Tip: TAR ONLY THE FILES

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Unix Tip 3053 - June 16, 2010

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TAR ONLY THE FILES

To tar only files (not
subdirectories) in the
current directory use
this command:

$ tar cvf files.tar ./`ls -l | grep -v '^d' | awk '{ print $9 }'`

This tip generously supported by: rrs@assc.com.ve

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Selasa, 15 Juni 2010

Unix Tip: SHELL OUTPUT INTO VI

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Unix Tip 3052 - June 15, 2010

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SHELL OUTPUT INTO VI

In VI editor you can get
the output of any shell
command command inserted
into the file you are
editing by using:

:r!<command>

For example:

:r!who -r

inserts the ouput of the
command "who -r" to the
file currently being
edited.

This can be effectively used
to copy the contents of a
file to the file currently
being edited

ie,

:r!cat /etc/passwd

inserts all the contents of
the the /etc/passwd to the
file currently being edited.

This tip supported by: Prem Kumar S <sprem@wipro.co.in>

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Senin, 14 Juni 2010

Unix Tip: AVOID PERMISION DENIED

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Unix Tip 3051 - June 14, 2010

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AVOID PERMISION DENIED

To avoid 'Permission Denied'
messages when using the
'find' command:

in ksh :-
find <dir> -name '<file>' -print 2 > /dev/null

in csh :-
(find <dir> -name '<file>' -print >/dev/tty) >& /dev/null

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Minggu, 13 Juni 2010

Unix Tip: PROGRESS STATUS IN XTERM TITLEBAR

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UNIX HOT TIP

Unix Tip 3050 - June 13, 2010

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PROGRESS STATUS IN XTERM TITLEBAR

Sometimes it is handy to be able
to show some information in the
xterms title bar, for example
if you download a set of large
files (thereby producing lots
of meaningless information on
the terminal) and you want to
know which file is actually
beeing downloaded.

For this purpose, I hacked a few
lines of shell code that would
put any information into the
xterms title bar. I called the
script ttshow.

#!/bin/sh
if [ -z $DISPLAY ]; then
echo "ESC]0; $* ^G"
fi

In this little script, the
string ESC has to be replaced
by one real escape character
(ascii 0x1b), the string "^G"
has to be replaced by a bel
character (ascii 0x07).

Now I can make my scripts like
this:

for file in in `cat filenames`; do
ttshow "downloading $file"
wget $file
done

..and it will tell me on the
first glance what it's doing.

For more information about
this, unpack the X distribution
and search for the file
ctlseqs.ms - this file belongs
to the xterm distribution and
contains all the escape
sequences xterm knows about.

This tip generously supported
by: ulinzen+ugu@sendmail.com

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Sabtu, 12 Juni 2010

Unix Tip: HP-UX REMOVE UNUSED SPACE

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UNIX HOT TIP

Unix Tip 3049 - June 12, 2010

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HP-UX REMOVE UNUSED SPACE

To remove unused s/w and free
disk space in hp-ux use the
command:

freedisk [-a n] [-v]

Note: See man page for this
before executing this..

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Jumat, 11 Juni 2010

Unix Tip: FILE SYSTEM CAPACITY ALERT

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UNIX HOT TIP

Unix Tip 3048 - June 11, 2010

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FILE SYSTEM CAPACITY ALERT

#!/bin/sh
# This script can be used to
# warn the users that
# the file system is getting full
#
# Script needs adjusted for your
# needs. Below is set to monitor
# all the file systems mounted and report to
# RECEIVER
#
# Usage: as a cron entry for best use.

RECEIVER=nachiappan.ramanathan@aig.com

for fs in `df -k|awk '{print $1}'|sed -n "3,14 p"`
do
x=`df -kl | grep $fs | awk '{ print $5 }'`
y=50%

if [ $x -gt $y ]
then
message="File System `df -k |grep $fs |awk '{print $6\",
\"$5}'` Full!!!"
echo $subject
echo $message | mailx -s "`hostname` - File System Full
Warning !!!" $RECEIVER
fi
done

This tip generously supported by:
Nachiappan.Ramanathan@aig.com

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Kamis, 10 Juni 2010

Unix Tip: Tru64 STTY DEC

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UNIX HOT TIP

Unix Tip 3047 - June 10, 2010

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Tru64 STTY DEC

On Tru64 Unix (at least on 4.0F),
some non-root-user drop an error
message on the root's Mail
account when cronjobs used

su - foo -c /usr/bin/bar

Even some Compaq technicians could
not tell that this results from
terminal settings in the .profile,
which are invalid on non-interactive
terminals. The error messages
(2 in fact) looks like this:

stty: tcgetattr: not a typewriter
Not a terminal.

The solution is to wrap commands
like "stty dec" and "tset -I -Q"
with a check on terminal capabilities:

if tty -s
then
stty dec
tset -I -Q
fi

This tip generously supported by: nils@poppendiek.de

Unix Guru Universe - www.ugu.com - tips@ugu.com - Copyright 1994-2001
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Rabu, 09 Juni 2010

Unix Tip: KEEPING PEOPLE OUT

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UNIX HOT TIP

Unix Tip 2474 - October 10, 2005

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KEEPING PEOPLE OUT

If you want to keep people of your server, but want them to access their pop mail on the same box set up the following line in the password file:

babba:rtnRkIgCy4l4T:830:10:Babba Booie:/home/babba:/bin/nologin

Then create a script called /bin/nologin that contains:

#! /bin/sh
echo "Sorry, but your account is only allowed POP access to this host."
exit 1

when a person attempts to log into their defined shell it will run the /bin/noling script, display the message, and exit them from the system

Have Fun

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Unix Tip: ELIMINATING MULTIPLE SPACES

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UNIX HOT TIP

Unix Tip 3046 - June 9, 2010

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ELIMINATING MULTIPLE SPACES

Here is a simple script which
helps in eliminating multiple
spaces when one wants to
extract a particular column
in a set of records from a
file.

Here is an example to prove
the same:

ps -u $LOGNAME | tr -s " " : | cut -d: -f<column #>

The above script line can be
used to extract a column from
the output of a ps command for
a particular user ($LOGNAME).

This tip generously supported by: arunkv@lucent.com

Unix Guru Universe - www.ugu.com - tips@ugu.com - Copyright 1994-2001
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Selasa, 08 Juni 2010

Unix Tip: FINDING PCI DEVICES

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UNIX HOT TIP

Unix Tip 3045 - June 8, 2010

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FINDING PCI DEVICES

Want to get information on PCI devices on your Linux or FreeBSD machine?

On Linux use:

/sbin/lspci (-v is verbose)

On FreeBSD use:

pciconf -l

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Senin, 07 Juni 2010

Unix Tip: HANGING TIME ON HPUX

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UNIX HOT TIP

Unix Tip 3044 - June 7, 2010

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HANGING TIME ON HPUX

How can we change the time zone on a HP-UX machine ??

Answer : -Edit the entry
in /etc/src.sh and
/etc/src.csh, and
reboot

This tip generously supported by: anil_sedha@mumbai.tcs.co.in

Unix Guru Universe - www.ugu.com - tips@ugu.com - Copyright 1994-2001
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Minggu, 06 Juni 2010

Unix Tip: FINDING MAC ADDRESS ON HP

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UNIX HOT TIP

Unix Tip 3043 - June 6, 2010

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FINDING MAC ADDRESS ON HP

If you want to know the MAC or eathernet address of your lan card on an HP-UX machine, then type:

lanscan

This will give you the mac addresses of all the lan cards installed on the machine.

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Sabtu, 05 Juni 2010

Unix Tip: MAX FILES UNDER LINUX

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UNIX HOT TIP

Unix Tip 3042 - June 5, 2010

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MAX FILES UNDER LINUX

Maximum number of files that one process can have open at one time can be find out by using:

getconf OPEN_MAX

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Jumat, 04 Juni 2010

Unix Tip: WHY MV IS SLOW

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UNIX HOT TIP

Unix Tip 3041 - June 4, 2010

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WHY MV IS SLOW

mv command across filesystems is slower on large files

WHY?

mv would be slow if you are moving files across filesystem.

The inode number changes only when a file is moved across file system.

A new inode number means a new file is physically created on disk.

It remains unchanged, if it is within the same filesystem. One can verify by using ls -il command on that file.

mv uses rename() system call. if it fails, it uses copy routine (basicailly reads from a file and writes in another file).

mv command across filesystem is more of a copy then mv.

This tip generously supported by: dkotian1@rediffmail.com

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Kamis, 03 Juni 2010

Unix Tip: ECHO LINES TO A BLANK

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UNIX HOT TIP

Unix Tip 3040 - June 3, 2010

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ECHO LINES TO A BLANK

To echo all lines in a file upto the first blank line use the following:

awk '$0 ~ /^$/ {exit;} {print $0;}' <file_name>

The awk script can be used for printing lines upto the first occurence of any pattern.

Just substitute ^$ with the pattern.

I wrote this script to parse http server headers.

This tip generously supported by: anand@anandraman.net

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Rabu, 02 Juni 2010

Unix Tip: STAT FILES

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UNIX HOT TIP

Unix Tip 3039 - June 2, 2010

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STAT FILES

Not supported on all flavors.

To see inode contents (file size, allocated blocks, file type, user, group, file mode, last accessed, last modified etc) of a file:

$ stat file1 file2 fileN

This tip generously supported by: sachin_m_joshi@yahoo.com

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Selasa, 01 Juni 2010

Unix Tip: AWK THE STATS

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UNIX HOT TIP

Unix Tip 3038 - June 1, 2010

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AWK THE STATS

AWK script for getting statistics.

The script gives the statistics of the default shell set for the users.

i.e. Number of users using csh,ksh or sh

$cat stat_demo.awk
#start here
BEGIN{
FS=":"
#seperator is set to :
}
{
#$7, is 7 field in passwd file
stat_array[$7]=stat_array[$7]+1;
}
END{
print "Login-Shell Count" ;
for (i in stat_array) print i, stat_array[i]
#Displays statistics
}