Unix and Linux Tips

Rabu, 11 Januari 2012

Unix Tip: VI COPY FILE TO FILE

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UNIX GURU UNIVERSE
UNIX HOT TIP

Unix Tip 3259 - January 11, 2012

http://www.ugu.com/sui/ugu/show?tip.today

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VI COPY FILE TO FILE

Here is how to copy the required number
of lines from one file to another in
VI editor. First use the following
key combinations in the source file.

Press ESCAPE
Press Shift "(Shift double quotes)
Press a
Press the number of lines you want to copy
press y followed by another y

Now press " : " (COLON) to get the vi prompt.
Hit e "Destination file name"
Once you enter the Destination file
go to the line where you want the lines
copied to be inserted.

Press ESCAPE.
Press SHIFT "(Double quotes).
Press a.
Press p.

The lines get copied.

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Selasa, 10 Januari 2012

Unix Tip: SEARCH SEVERAL FILES

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UNIX GURU UNIVERSE
UNIX HOT TIP

Unix Tip 3258 - January 10, 2012

http://www.ugu.com/sui/ugu/show?tip.today

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SEARCH SEVERAL FILES

To search several files for a
string which you know sparsely,
the following searching technique
would be useful:

#grep <first part>.*<second part>.*<... part> <filenames>
or,
#ls|xargs grep <first part>.*<second part>.*<... part>

This will print all the filenames
and lines which consists of
"<first part><0 to any number of
characters><second part><0 to any
number of characters><third part>
......"

For example, you want to search a
data structure among several header
files where it has been declared
not where it is being used.

If the data structure be XYZ, then
search will be:

#grep }.*XYZ <filenames>

because you know it might be how
XYZ has been declared,
struct {
.....
.....
} XYZ
You don't know exactly how many
blank characters are there
unless you count them. But when XYZ
will be used it will be
done as follows(for example):

XYZ *xyz;

and you don't want them to find out
as they will be coming
in several header or C files.

This tip generously supported by: dipakb@cdotd.ernet.in

Unix Guru Universe - www.ugu.com - tips@ugu.com - Copyright 1994-2001
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Senin, 09 Januari 2012

Unix Tip: ARITHMETIC COMPARISON

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UNIX GURU UNIVERSE
UNIX HOT TIP

Unix Tip 3257 - January 9, 2012

http://www.ugu.com/sui/ugu/show?tip.today

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ARITHMETIC COMPARISON

In UNIX shell arithmetic comparison
is limited to integer values. Here
is a tip to compare floating values
using basic shell commands.

--------- CUT HERE-----------------

#! /bin/sh
# test shell script
n1="01.401"
n2="01.350"

function compareFloatSmall
{
sort -n <<: | head -1
$n1
$n2
:
}

function compareFloatGreat
{
sort -r -n <<: | head -1
$n1
$n2
:
}

small=$(compareFloatSmall $n1 $n2)
echo "Comparing $n1 to $n2: smaller $less"
great=$(compareFloatGreat $n1 $n2)
echo "Comparing $n1 to $n2: greater $great"

--------- CUT HERE-----------------

Alternatively you can use a small 'awk' program.

--------- CUT AGAIN HERE-----------
#! /bin/sh
# A couple of examples in awk.
n1="03.550"
n2="02.550"

echo "$n1 $n2" | awk '{
if ( $1 >= $2 ) print $1
if ( $1 <= $2 ) print $2
if ( $1 > $2 ) print $1
if ( $1 < $2 ) print $2
if ( $1 == $2 ) print $1, $2
}'
--------- CUT AGAIN HERE-----------

This tip generously supported by: sthackeray@netscape.net

Unix Guru Universe - www.ugu.com - tips@ugu.com - Copyright 1994-2001
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Minggu, 08 Januari 2012

Unix Tip: COPY A TREE WITH CPIO

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UNIX GURU UNIVERSE
UNIX HOT TIP

Unix Tip 3256 - January 8, 2012

http://www.ugu.com/sui/ugu/show?tip.today

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COPY A TREE WITH CPIO

Using standard UNIX tar to copy a
tree doesn't preserve the original
owner and group information for the
directories and files during the copy.
To do this, use find(1) piped to cpio(1)
this way:

% cd <source-directory>
% find . -depth -print | cpio -pudm <dest-directory>

This will create a mirror image of the
<source-directory> tree in <dest-directory>.

Unix Guru Universe - www.ugu.com - tips@ugu.com - Copyright 1994-2001
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