We use a UNIX-based system (Lawson) at work and I was given this command to request a data extract from the db admin. The only thing I really understand is the last line as it appears to be joining the files created from the first three lines into one. Is there anyone who can help me breakdown the... (4 Replies)
# sub: find block (in cols), return line-numbers (begin-end) or 0 if notfound
sub findb{
my ($exp1,$col1,$exp2,$col2)= @_; # $exp = expression to find, $col - column to search in
my $cnt=0;
my ($val1,$val2);
my ($beg,$end);
for($cnt=1;$cnt<=65536;$cnt++){
$val1 =... (3 Replies)
i am analyzing a query written by another developer ,need to understand part of script
am looking at a code ..and it converts comma files to pipe delimited and also takes away quotes from any columns,
source field format: 2510,"Debbie",NewYork
changes to
target: 2510|Debbie|NewYork
... (1 Reply)
Can someone explain what is happening line by line in this script, particularly after the do statement. The script works, it renames all the files in my directory that has a date in the file name. But I would like to know more about it.
#!/bin/bash
newdate=12-10-1995
for file in *--*
do
... (6 Replies)
i am trying to understand this script example. the text does not explain it. can someone tell me briefly what each of the functions do. any help will be appreciated.
#!/bin/bash
killtree() {
local _pid=$1
local _sig=${2-TERM}
for _child in $(ps -o pid --no-headers --ppid... (1 Reply)
Hi Guys,
I am new to scripting , I am trying to rebuild a script based on an old script. Can someone help me figure out what the script is doing? This is only a part of the script.
I am looking to interpret these two points in the scripts:-
1)
test=`echo $?`
while
I do not... (3 Replies)
Could someone please help me in understanding the code below:
#!/usr/bin/ksh
Month=`date|cut -c5-7`
Day=`date|cut -c9-10`
Year=`date|cut -c27-28`
Rom2Jul() { case $Month in Feb) Day=$(( $Day+31 ));;
Mar) Day=$((... (27 Replies)
Below script is called as Reducer, I am not sure how it work, can some expert explain me what this script does as i am a beginner.
inputfile:
hi hi how are are you
code:
#!/bin/bash
lastkey=""; -- what does this mean, because i saw in debug mode it is taking value as hi
count=0;... (13 Replies)
Hello,
How come the following script adds each numeric value to a total sum ?
x=$1
func()
{
for i in $1 $2 $3; do
let x= $x+$i
done }
func "8 8 8" 9 9
echo $x
A.How the program sums the string "8 8 8" if it`s only the first field value ($1)?
B.If we define x to be $1... (3 Replies)
Discussion started by: uniran
3 Replies
LEARN ABOUT DEBIAN
bup-margin
bup-margin(1) General Commands Manual bup-margin(1)NAME
bup-margin - figure out your deduplication safety margin
SYNOPSIS
bup margin [options...]
DESCRIPTION
bup margin iterates through all objects in your bup repository, calculating the largest number of prefix bits shared between any two
entries. This number, n, identifies the longest subset of SHA-1 you could use and still encounter a collision between your object ids.
For example, one system that was tested had a collection of 11 million objects (70 GB), and bup margin returned 45. That means a 46-bit
hash would be sufficient to avoid all collisions among that set of objects; each object in that repository could be uniquely identified by
its first 46 bits.
The number of bits needed seems to increase by about 1 or 2 for every doubling of the number of objects. Since SHA-1 hashes have 160 bits,
that leaves 115 bits of margin. Of course, because SHA-1 hashes are essentially random, it's theoretically possible to use many more bits
with far fewer objects.
If you're paranoid about the possibility of SHA-1 collisions, you can monitor your repository by running bup margin occasionally to see if
you're getting dangerously close to 160 bits.
OPTIONS --predict
Guess the offset into each index file where a particular object will appear, and report the maximum deviation of the correct answer
from the guess. This is potentially useful for tuning an interpolation search algorithm.
--ignore-midx
don't use .midx files, use only .idx files. This is only really useful when used with --predict.
EXAMPLE
$ bup margin
Reading indexes: 100.00% (1612581/1612581), done.
40
40 matching prefix bits
1.94 bits per doubling
120 bits (61.86 doublings) remaining
4.19338e+18 times larger is possible
Everyone on earth could have 625878182 data sets
like yours, all in one repository, and we would
expect 1 object collision.
$ bup margin --predict
PackIdxList: using 1 index.
Reading indexes: 100.00% (1612581/1612581), done.
915 of 1612581 (0.057%)
SEE ALSO bup-midx(1), bup-save(1)BUP
Part of the bup(1) suite.
AUTHORS
Avery Pennarun <apenwarr@gmail.com>.
Bup unknown-bup-margin(1)