07-21-2014
Thanks Chako193
10 More Discussions You Might Find Interesting
1. UNIX for Dummies Questions & Answers
Please explain this command line ?
wc<infile<newfile
Thanx,
Saneesh Joseph. (2 Replies)
Discussion started by: saneeshjose
2 Replies
2. UNIX for Dummies Questions & Answers
Explain the output of the command “sort -rfn file1 | more” (1 Reply)
Discussion started by: wickbc
1 Replies
3. Shell Programming and Scripting
Hi all ,
please explain the following command :
perl -e 'select(undef,undef,undef,.15)'
Thanks and Regards
Navatha (2 Replies)
Discussion started by: Navatha
2 Replies
4. UNIX for Dummies Questions & Answers
Specifically what is the purpose of sed?
What is f?
Why is the 'cp f $phonefile' line needed when the script ‘goes live'?
Why might that two commands following sed be commented out at the present time ( i.e., during development)?
Thanks in... (2 Replies)
Discussion started by: knp808
2 Replies
5. Shell Programming and Scripting
find . -type f -ctime +3 -exec mv {} /somedirectory/ \;
in particular "-ctime v/s -mtime" and "difference between +3 and -3" (5 Replies)
Discussion started by: Rambo
5 Replies
6. Shell Programming and Scripting
I am using this line of perl code to change the file format and remove ^M at the end of each line in files:
perl -i -pe's/\r$//;' <name of file here>
Can you explain to me what this code does, and translate it into bash/awk/sed? (2 Replies)
Discussion started by: locoroco
2 Replies
7. UNIX for Dummies Questions & Answers
Hi,
I saw this. But I don't know why we need this?
ls mydir > foo.txt ## I know what this will do, it will take the results and write to the file called foo.txt
ls mydir > foo.txt 2>&1 ## Don't know why we need 2>&1
Thanks. (2 Replies)
Discussion started by: samnyc
2 Replies
8. UNIX for Dummies Questions & Answers
Please explain grep -A 999999. I've seen this before, it always seems to be with six 9's as well. See an example below.
grep 'regexp' -A 999999 server.log | egrep -c 'Option=\' (6 Replies)
Discussion started by: scj2012
6 Replies
9. Shell Programming and Scripting
Hi Forum.
I have the following script /home/user/EDW_ENV.sh to setup some environment variables as:
##### section 1 PM_HOME #####
export PC_DIR_BASE=/data/informatica/ming
export DIR_ORACLE=/data/sw/apps/oracle/Oracle_scripts
export... (4 Replies)
Discussion started by: pchang
4 Replies
10. UNIX for Beginners Questions & Answers
I have a requirement to remove all non-ascii characters from a fixed length file. I used the below command which is removing special characters but somehow the total record length is being truncated to one space less. If it is a multi-byte string then many characters at the end are being truncated.... (8 Replies)
Discussion started by: eskay
8 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)