Deleting extension from filename
Thomas Cameron
Hi all -
I am taking a shell scripting class, bu the prof fires off info at us
for about an hour and then leaves campus. We're supposed to be in lab
for two hours, but he's gone and the proctor won't help.
My problem is this: I need to write a ksh script called "unsuffix" that
will take two arguments, the first being a filename and the second being
the extension the user wants to strip from the filename. So if the user
types
unsuffix report.old .old
he will remove the .old extension and the user will be left with a file
called "report."
I haven't a clue how to do it. I started with cut, and crapped out. He
said we woulf be able to do it with sed, but I don't know how.
Any help greatly appreciated.
Thomas
Herve Couppe de Lahongrais - CDL
A command exists whose purpose is exactly what you want : basename
--
Herve Couppe de Lahongrais (SEU) | Eurocontrol Experimental Centre
mailto:c...@eurocontrol.fr | France
Josef Moellers
Thomas Cameron wrote:
>
> Hi all -
>
> I am taking a shell scripting class, bu the prof fires off info at us
> for about an hour and then leaves campus. We're supposed to be in lab
> for two hours, but he's gone and the proctor won't help.
>
> My problem is this: I need to write a ksh script called "unsuffix" that
> will take two arguments, the first being a filename and the second being
> the extension the user wants to strip from the filename. So if the user
> types
>
> unsuffix report.old .old
>
> he will remove the .old extension and the user will be left with a file
> called "report."
>
> I haven't a clue how to do it. I started with cut, and crapped out. He
> said we woulf be able to do it with sed, but I don't know how.
>
> Any help greatly appreciated.
> Thomas
Just think about what you need to do:
You need to subtitute the suffix (which has to be at the end of the
filename) with ... nothing.
Add to this the fact that "echo" will send its arguments to standard
output and "sed" reads from standard input, makes substitutions and
writes the (possibly modified) line(s) to standard output and an
unmatched substitution is no failure.
This will lead you to the one-line shell script that does it all.
The actual implementation (25 characters, no checks for usage) is left
up to the reader as an exercise.
Hope this helps,
Josef
--
Josef Moellers molle...@sni.de
PS Dieser Artikel enthaelt einzig und allein meine persoenlichen
Ansichten!
PS This article contains my own, personal opinion only!
Douglas Wilson
Josef Moellers wrote:
>
> > unsuffix report.old .old
> >
> > he will remove the .old extension and the user will be left with a file
> > called "report."
"sed" reads from standard input, makes substitutions and
> writes the (possibly modified) line(s) to standard output and an
> unmatched substitution is no failure.
> The actual implementation (25 characters, no checks for usage) is left
> up to the reader as an exercise.
as long as you're using ksh, here's an even shorter solution:
#!/bin/ksh
mv $1 ${1%${2}}
Cheers,
Douglas Wilson
Peter H. Larsen
Hi Thomas,
In ksh I would do this:
echo ${FILE%EXT}
where $FILE is the filename and $EXT is the extension.
- Peter H. Larsen
Thomas Cameron wrote:
> Hi all -
>
> I am taking a shell scripting class, bu the prof fires off info at us
> for about an hour and then leaves campus. We're supposed to be in lab
>
> for two hours, but he's gone and the proctor won't help.
>
> My problem is this: I need to write a ksh script called "unsuffix"
> that
> will take two arguments, the first being a filename and the second
> being
> the extension the user wants to strip from the filename. So if the
> user
> types
>
> unsuffix report.old .old
>
> he will remove the .old extension and the user will be left with a
> file
> called "report."
>
Christian Weisgerber
Josef Moellers <molle...@sni.de> writes:
> > unsuffix report.old .old
> > He said we woulf be able to do it with sed, but I don't know how.
>
> Add to this the fact that "echo" will send its arguments to standard
> output and "sed" reads from standard input, makes substitutions and
> writes the (possibly modified) line(s) to standard output and an
> unmatched substitution is no failure.
>
> This will lead you to the one-line shell script that does it all.
I'd love to see that shell script, because I can only think of one where
sed metacharacters in the suffix would wreak havoc.
--
Christian 'naddy' Weisgerber na...@mips.rhein-neckar.de
See another pointless homepage at <URL:http://home.pages.de/~naddy/>.
Al Aab
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my favourite DOS/UNIX sed15 (with C source)
(easily compilable for UNIX. has friendly extenstions/relaxations like hex)
ftp://uiarchive.uiuc.edu/pub/systems/pc/simtelnet/msdos/txtutl/sed15.zip
ftp://uiarchive.uiuc.edu/pub/systems/pc/simtelnet/msdos/txtutl/sed15x.zip
Directory: /pub/systems/pc/simtelnet/msdos/txtutl/
Filename Type Length Date Description
===============================================================================
sed15.zip B 62082 910930 Unix-compatible streaming editor v1.5 TC src
sed15x.zip B 20300 910930 Unix-compatible streaming editor v1.5 EXE/docs
sed15.zip has C source, compilable for UNIX.
Also, check simtel for u-sedit. has nice docs.
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(then he sed: not by sed alone ... lives man)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Douglas Wilson (dgwi...@gte.net) wrote:
: Josef Moellers wrote:
: >
: > > unsuffix report.old .old
: > >
: > > he will remove the .old extension and the user will be left with a file
: > > called "report."
: "sed" reads from standard input, makes substitutions and
: > writes the (possibly modified) line(s) to standard output and an
: > unmatched substitution is no failure.
: > The actual implementation (25 characters, no checks for usage) is left
: > up to the reader as an exercise.
: as long as you're using ksh, here's an even shorter solution:
: #!/bin/ksh
: mv $1 ${1%${2}}
: Cheers,
: Douglas Wilson
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Tapani Tarvainen
Josef Moellers <molle...@sni.de> writes:
> Thomas Cameron wrote:
> > My problem is this: I need to write a ksh script called "unsuffix" that
> > will take two arguments, the first being a filename and the second being
> > the extension the user wants to strip from the filename. So if the user
> > types
> >
> > unsuffix report.old .old
> >
> > he will remove the .old extension and the user will be left with a file
> > called "report."
> Just think about what you need to do:
> You need to subtitute the suffix (which has to be at the end of the
> filename) with ... nothing.
>
> Add to this the fact that "echo" will send its arguments to standard
> output and "sed" reads from standard input, makes substitutions and
> writes the (possibly modified) line(s) to standard output and an
> unmatched substitution is no failure.
>
> This will lead you to the one-line shell script that does it all.
Yes. Besides sed you can do it with any number of utilities
including (but not limited to) basename, cut, awk and perl,
but the easiest and shortest is way is to use ksh's ${VAR%pattern}
substitution feature (no external commands needed except mv).
> The actual implementation (25 characters, no checks for usage) is left
> up to the reader as an exercise.
Ditto (with even less characters, maybe ~15).
--
Tapani Tarvainen
Josef Moellers
Christian Weisgerber wrote:
>
> Josef Moellers <molle...@sni.de> writes:
> > This will lead you to the one-line shell script that does it all.
>
> I'd love to see that shell script, because I can only think of one where
> sed metacharacters in the suffix would wreak havoc.
Yep, you're right. I was only looking at the original poster's example.
Even then, my script would match
fileext .ext
which is incorrect.
I'm sorry.
If you parsed the extension and replaced all metacharacters ... Ah well,
I was wrong.
Dominic Lucas
In article <33BCFC47...@novo.dk>, "Peter H. Larsen" <pl...@novo.dk> writes:
|> Hi Thomas,
|>
|> In ksh I would do this:
|>
|> echo ${FILE%EXT}
|>
|> where $FILE is the filename and $EXT is the extension.
|>
|> - Peter H. Larsen
|>
|> Thomas Cameron wrote:
|>
|> > Hi all -
|> >
|> > I am taking a shell scripting class, bu the prof fires off info at us
|> > for about an hour and then leaves campus. We're supposed to be in lab
|> >
|> >
|>
A better (no, I mean simpler ...) way would be
basename <filename> <extension>
so basename report.old .old
would return
report
this implies, however, that you know the suffix, which I think matches your case
Dom
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----
Opinions expressed in this mail are mine, and not necessarily that of
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----
Dominic Lucas - Siemens Nixdorf BU ITS Unix
Tel: +44 1344 850335
Email : Domini...@sni.co.uk
Home: d...@patrol.i-way.co.uk
WWW: http://www.i-way.co.uk/~dom/
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----