Date: Sat, 6 Jun 1998 20:27:18 -0400 (EDT) From: Adrian Filipi-Martin <adrian@nvl.virginia.edu> To: Slyce <slyce@onramp.net> Cc: FreeBSD Questions <questions@FreeBSD.ORG> Subject: Re: BASH script help... Message-ID: <Pine.HPP.3.96.980606202056.1323A-100000@huron.nvl.virginia.edu> In-Reply-To: <3579411C.25FB6F54@onramp.net>
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On Sat, 6 Jun 1998, Slyce wrote:
> I'm creating a script to backup some files under dos in a tarball.... I
> want to be able to save the last five backups.... I'm saving them in
> dos_backup_060198_073456_1.tar.gz format.... How can I strip the tar.gz
> and increment the 1 to 2....
> For instance, I have dos_backup_060198_073456_1.tar.gz and
> dos_backup_060298_073456_2.tar.gz and just created a new backup file,
> but need to rename the previous two by incrementing the last number by
> one, so the old dos_backup_060198_073456_1.tar.gz becomes
> dos_backup_060198_073456_2.tar.gz, the old
> dos_backup_060298_073456_3.tar.gz becomes
> dos_backup_060298_073456_3.tar.gz and the new one is
> dos_backup_060398_073456_1.tar.gz....
Here's an example of how to split up a string in bash and
reconstruct a filename with the new version number. See the "parameter
expansion" section of the bash man page for details on the ${foo%bar} and
${foo#bar} expansion semantics. 'let' makes it clear that you are
defining an arithmetic variable, but normally you use $((...)) to do
inline arithmetic.
: adrian@huron; File=test_1.tar.gz
: adrian@huron; echo ${File}
test_1.tar.gz
: adrian@huron; Base=${File%%.*}
: adrian@huron; echo ${Base}
test_1
: adrian@huron; let NewVersion=${Base##*_}+1
: adrian@huron; echo ${NewVersion}
2
: adrian@huron; NewFile=${Base%_*}_${NewVersion}.tar.gz
: adrian@huron; echo ${NewFile}
test_2.tar.gz
: adrian@huron;
N.B. ": adrian@huron;" is my prompt. It's a NOP, ':' is the null
command and ';' is the command separator, so everything between are
arguments. It's means you can paste an entire command line, including the
prompt, into a terminal window. It makes selecting and pasting commands
simipler IMHO, i.e. just tripple click and then middle click.
Adrian
--
adrian@virginia.edu ---->>>>| If I were stranded on a desert island, and
System Administrator --->>>| I could only have one OS for my computer,
Neurosurgical Visualization Lab ->>| it would be FreeBSD. Think about it.....
http://www.nvl.virginia.edu/ ->| http://www.freebsd.org/
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