03-14-2002
i don't understand the "sort" command
i have been trying to understand this chapter titled "Searching for Files and Text" for a few weeks now.
unfortunately, this chapter is one of those things, that no matter how hard you try and how long you try for, you are incapable of understanding (at least in my case)
this entire chapter, grep and it's derivatives and the sort command have been extremely frustrating.
i am hung up on the sort command more so than the others, but there are certain features that are especially difficult to understand.
this is what the book says about the sort command:
sort -options filenames(s)
the following two options are killing me:
-n performs a numeric sort.
(+|-)n begins (+n) or ends (-n) the sort with the field following the n
field
consider the following two examples, that have 8 columns (do columns=fields ?):
sort -rn +4 list -o num.list
sort -rn -3 list -o num2.list
sort +5n list -o update.list
first i would like some clarification with the (+|-)n option.
in the first example, the +4 says that we start counting from the 5th field (5th field because we start counting from 0, not 1 right?)... so when we count, we use fields 5,6,7 right?
in the second example, the -3 says we start counting from the 4th field backwards right? so 3,2,1,0?
next, i'm confused with what I see with the first two examples and the last. I notice that in the first two examples the +/- numbers (+4 and -3) are isolated options, but in the last example, +5n, the two options I mentioned earlier are combined. I don't understand why this is done, or what it means. shouldn't it be +5 -n instead of +5n? is +5 -n different from +5n?
can anyone please help reduce my confusion with this command?
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LEARN ABOUT DEBIAN
dvdbackup
dvdbackup(1) General Commands Manual dvdbackup(1)
NAME
dvdbackup - Tool to backup DVDs
SYNOPSIS
dvdbackup [OPTION]...
DESCRIPTION
This manual page documents briefly the dvdbackup command. This manual page was written for the Debian distribution because the original
program does not have a manual page. dvdbackup is a tool to extract data from video DVDs. It has the advantages of being small, fast, and
easy to use.
OPTIONS
A summary of options is included below.
-h, --help
print a brief usage message
-V, --version
print version information
-I, --info
for information about the DVD
-M, --mirror
backup the whole DVD
-F, --feature
backup the main feature of the DVD
-T X, --titleset=X
backup title set X
-t X, --title=X
backup title X
-s X, --start=X
backup from chapter X
-e X, --end=X
backup to chapter X
-i DEVICE, --input=DEVICE
where DEVICE is your DVD device. This switch only needs to be used if your DVD device node is not /dev/dvd
-o DIRECTORY, --output=DIRECTORY
where DIRECTORY is your backup target. If not given, the current working directory will be used.
-v, --verbose
print more information about progress
-n NAME, --name=NAME
(optional) set the title - useful if autodetection fails
-a 0, --aspect=0
to get aspect ratio 4:3 instead of 16:9 if both are present
-r {a,b,m}, --error={a,b,m}
select read error handling: a=abort, b=skip block, m=skip multiple blocks (default)
-p, --progress
print progress information while copying VOBs
Option notes
-a is option to the -F switch and has no effect on other options
-s and -e should preferably be used together with -t
General backup information
If your backup directory is /my/dvd/backup/dir/ specified with the -o flag, then dvdbackup will create a DVD-Video structure under
/my/dvd/backup/dir/TITLE_NAME/VIDEO_TS. If the -o flag is omitted, the current directory is used.
Since the title is "unique" you can use the same directory for all your DVD backups. If it happens to have a generic title dvdbackup will
exit with a return value of 2, and you will need to specify a title name with the -n switch.
dvdbackup will always mimic the original DVD-Video structure. Hence if you e.g. use the -M (mirror) you will get an exact duplicate of the
original. This means that every file will have the same size as the original one. Likewise also for the -F and the -T switch.
However the -t and (-t -s/-e) switch is a bit different the titles sectors will be written to the original file but not at the same offset
as the original one since there may be gaps in the cell structure that we do not fill.
EXAMPLES
dvdbackup -I
gathers information about the DVD. /dev/dvd is the default device tried - you need to use -i if your device name is different.
dvdbackup -M
backups the whole DVD. This action creates a valid DVD-Video structure that can be burned to a DVD-/+R(W) with help of genisoimage.
dvdbackup -F
backups the main feature of the DVD. This action creates a valid DVD-Video structure of the feature title set. Note that this will
not result in an image immediately watchable - you will need another program like dvdauthor to help construct the IFO files.
dvdbackup defaults to get the 16:9 version of the main feature if a 4:3 is also present on the DVD. To get the 4:3 version use -a
0.
dvdbackup makes it best to make a intelligent guess what is the main feature of the DVD - in case it fails please send a bug report.
dvdbackup -T 2
backups the title set 2 i.e. all VTS_02_X.XXX files. This action creates a valid DVD-Video structure of the specified title set.
Note that this will not result in an image immediately watchable - you will need another program like dvdauthor to help construct
the IFO files.
dvdbackup -t 1
backups the title 1. This action backups all cells that forms the specified title. Note that there can be sector gaps in between
one cell and another. dvdbackup will backup all sectors that belongs to the title but will skip sectors that are not a part of the
title.
dvdbackup -t 1 -s 20 -e 25
This action will backup chapter 20 to 25 in title 1, as with the backup of a title there can be sector gaps between one chapter
(cell) and on other. dvdbackup will backup all sectors that belongs to the title 1 chapter 20 to 25 but will skip sectors that are
not a part of the title 1 chapter 20 to 25.
To backup a single chapter e.g. chapter 20 do -s 20 -e 20.
To backup from chapter 20 to the end chapter use only -s 20.
To backup to chapter 20 from the first chapter use only -e 20.
You can skip the -t switch and let the program guess the title although it is not recommended.
If you specify a chapter that is higher than the last chapter of the title dvdbackup will truncate to the highest chapter of the
title.
EXIT STATUS
0 on success
1 on usage error
2 on title name error
-1 on failure
AUTHORS
dvdbackup was written by Olaf Beck <olaf_sc@yahoo.com>, but is now maintained by Benjamin Drung <benjamin.drung@gmail.com> and Stephen Gran
<sgran@debian.org>. This manual page was written by Stephen Gran <sgran@debian.org>.
0.2 2008-03-18 dvdbackup(1)