[[ ]] and [ ] work similar, but the implementation is different.
The [ is a builtin command. In fact it is an alias of the test command. (When run as [ the last argument must be ]. Command arguments may be redirected with < and >, and that is what caused your problem. The redirection can be prevented by quoting "<"">" or \<\>, but the standard operators are -lt and -gt. As with all command arguments, you should use "quotes" to prevent word splitting and globbing.
The [[ ]] is a compound, built into the shell interpreter. Because it is not a command, its content can be freely designed, and in fact a < and > are valid integer comparators. And the values are not subject to globbing, and word splitting happens before variable substitution (i.e. you need to quote "two words" to be seen as one value but not $word even if it's value is "two words").
These 2 Users Gave Thanks to MadeInGermany For This Post:
Hi,
I'm trying to use sed within a shell script (bash, running ubuntu). The command works fine from the command line, but when I use it within the script, rather than creating a file with the name I've specified, it creates one that ends with a question mark '?' when you use ls, e.g.... (3 Replies)
I have a script that runs ditto for me, and occasionally (if I exit the script while ditto is running in the background) it will leave an empty file named 0 in the script's directory. The next time I run the script, it generates incorrect data because of this file. I know I can easily insert a... (1 Reply)
I have a script that runs ditto for me, and occasionally (if I exit the script while ditto is running in the background) it will leave an empty file named 0 in the script's directory. The next time I run the script, it generates incorrect data because of this file. I know I can easily insert a... (1 Reply)
Hi All,
I have a script that does daily checks on my storage environment and is run from an AIX host.
The script currently works great but I have been changing and updating bits of it to make it easier for my lesser colleagues to understand :p
However now with the updates I have made I... (1 Reply)
I'm working on a project that requires me to compress then relocate directories to a different location based on their last date of modification. After running the script I check to see if it worked, and upon unzipping the tar.gz using I created everything that should be there is. I then performed... (4 Replies)
Hi,
I am trying to create a lock file with the following code but for some reason after file is created it has
wrong name "PASP?.lock??"
Please let us know how to get rid of these '??' from file name and from where they are coming?
#!/bin/ksh... (6 Replies)
I am new to Linux. Using latest version of Ubuntu.
I want to make a script that creates a 1GB file filled with zeros using dd and then formats the file as vfat with a label of "MYFILE".
If anyone can help me it would be appreciated. (9 Replies)
I have the following script
#!/bin/sh
Usage () {
echo "Usage: $0 <config_file>"
echo "Example: ./sftp_ondemand_daily.sh /export/data/mbsesb/config/ond
emand.cfg /export/data/mbsesb/config/filename.lst"
exit 1
}
if
then
Usage
fi
... (6 Replies)
I am new to Linux. Using latest version of Ubuntu.
I want to make a script that creates a 1GB file filled with zeros using dd and then formats the file as vfat with a label of "MYFILE".
If anyone can help me it would be appreciated. (1 Reply)
Discussion started by: amandasaza08
1 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)