CentOS - Aug 2012 - Cut command behaviour - bug or feature

Greetings,

I have a CSV file with three fields.
eg.

a1,b1,c1
a2,b2,c2
....

I wanted the output to be:
b1,c1,a1
b2,c2,a2
....

the command
cut -d, -f2,3,1 <file>

returns

a1,b1,c1

cut -d, -f2,3 <file>

works as advertised.

Is it specific to linux?

In that case how do I go about swapping two columns? I do not think a
gazzillion byte gui is required.

The file size is about 43Megs.

any ideas?

-- 
Regards,

Rajagopal

Rajagopal Swaminathan wrote:
> Greetings,
>
> I have a CSV file with three fields.
> eg.
>
> a1,b1,c1
> a2,b2,c2
> ....
>
> I wanted the output to be:
> b1,c1,a1
> b2,c2,a2
> ....
>
> the command
> cut -d, -f2,3,1 <file>
>
> returns
>
> a1,b1,c1
>
> cut -d, -f2,3 <file>
>
> works as advertised.
>
> Is it specific to linux?
>
> In that case how do I go about swapping two columns? I do not think a
> gazzillion byte gui is required.
>
> The file size is about 43Megs.
I've never been that good with cut. I'm going to see the author, Dave
Ihnat this weekend, who sometimes shows up here... but in the meantime,
you might use
awk 'BEGIN {FS=",";}{print $2 "," $3 ","
$1;}' infile

       mark

On 28.8.2012 21:59, Rajagopal Swaminathan wrote:
> Greetings,
> 
> I have a CSV file with three fields.
> eg.
> 
> a1,b1,c1
> a2,b2,c2
> ....
> 
> I wanted the output to be:
> b1,c1,a1
> b2,c2,a2
> ....
> 
> the command
> cut -d, -f2,3,1 <file>
> 
> returns
> 
> a1,b1,c1
cut cuts out, that what it does.
I think it works exactly as advertised.
On my system the manpage says

...snip
Selected input is written in the same order that it is
       read, and is written exactly once
snap...
> Is it specific to linux?
No!
-- 
Kind Regards, Markus Falb

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On Tue, Aug 28, 2012 at 2:59 PM, Rajagopal Swaminathan
<raju.rajsand at gmail.com> wrote:
> I have a CSV file with three fields.
> eg.
>
> a1,b1,c1
> a2,b2,c2
> ....
>
> I wanted the output to be:
> b1,c1,a1
> b2,c2,a2
> ....
>
> the command
> cut -d, -f2,3,1 <file>
>
> returns
>
> a1,b1,c1
>
> cut -d, -f2,3 <file>
>
> works as advertised.
>
> Is it specific to linux?
>
> In that case how do I go about swapping two columns? I do not think a
> gazzillion byte gui is required.
>
> The file size is about 43Megs.
>
> any ideas?
If you are sure that the fields will never contain commas, there are
any number of ways to split lines into variables in any number of
scripting languages including bash.   However, if the input is
'generic csv' that is allowed to have quotes around fields with
embedded commas it can be hard to parse.   I'd recommend perl with the
Text::CSV module so you don't have to deal with parsing yourself.

-- 
  Les Mikesell
    lesmikesell at gmail.com

On Wed, Aug 29, 2012 at 01:29:05AM +0530, Rajagopal Swaminathan
wrote:
> a1,b1,c1
> a2,b2,c2
> cut -d, -f2,3,1 <file>
Will not work.  The "-f" flag specifies what columns; not the order.
Everyone makes that mistake once :-)
> In that case how do I go about swapping two columns? I do not think a
> gazzillion byte gui is required.
Use "awk"
  awk -F, '{print $2 "," $3 "," $1}'

-- 

rgds
Stephen

On Wed, Aug 29, 2012 at 2:15 AM, Markus Falb <markus.falb at fasel.at>
wrote:
> On 28.8.2012 21:59, Rajagopal Swaminathan wrote:
>
> cut cuts out, that what it does.
> I think it works exactly as advertised.
> On my system the manpage says
>
> ...snip
> Selected input is written in the same order that it is
>        read, and is written exactly once
> snap...
>
See below
>> Is it specific to linux?
>
> No!
I would think, yes.

From:
http://www.unix.com/unix-dummies-questions-answers/117504-question-cut-command.html

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In AIX (for example) if you said

Code:
echo 1,2,3,4,5 | cut -d, -f3,1,5

you would get output as 3,1,5

But the cut command in Linux behaves differently.
>From the man page:
Quote:
Selected input is written in the same order that it is read, and is
written exactly once.

Which I think is poor. I can't see any way to do what you want with cut.

[unquote]

Thanks for everybody who pitched in

Any the issue got transformed into something else altogether.... (PHB,
vlookup 'experts' and the such for time being)

-- 

Regards,

Rajagopal