In shell, e.g. ksh,
I have input data of the form

a b c,x,c,d,
b c x,y

I'd need to process the 3rd column, how do I "explode" line by line?

On 2007-07-17, Ben wrote:
> In shell, e.g. ksh,
> I have input data of the form
>
> a b c,x,c,d,
> b c x,y
>
> I'd need to process the 3rd column, how do I "explode" line by line?

while read -r field1 field2 field3
do
: do whatever with "$field3"
done < FILENAME

If it is a large file, it may be more efficient to use sed or awk
rather than a shell loop.

--
Chris F.A. Johnson, author <http://cfaj.freeshell.org/shell/>
Shell Scripting Recipes: A Problem-Solution Approach (2005, Apress)
===== My code in this post, if any, assumes the POSIX locale
===== and is released under the GNU General Public Licence

Ben wrote:
> In shell, e.g. ksh,
> I have input data of the form
>
> a b c,x,c,d,
> b c x,y
>
> I'd need to process the 3rd column, how do I "explode" line by line?
>

You mean "explore" the line?

while read -r dummy dummy field3 ; do : anything with $field3 ; done <input


Janis

2007-07-17, 08:41(-07), Ben:
> In shell, e.g. ksh,
> I have input data of the form
>
> a b c,x,c,d,
> b c x,y
>
> I'd need to process the 3rd column, how do I "explode" line by line?

You use a tool that process input as fields. awk comes to mind.

awk '{whatever you want with $3}' < input-data

--
Stéphane

2007-07-17, 11:57(-04), Chris F.A. Johnson:
> On 2007-07-17, Ben wrote:
>> In shell, e.g. ksh,
>> I have input data of the form
>>
>> a b c,x,c,d,
>> b c x,y
>>
>> I'd need to process the 3rd column, how do I "explode" line by line?
>
> while read -r field1 field2 field3

that's
while read -r field1 field2 field3_and_above

use
while read -r field1 field2 field3 rest

if you want field3 only.

> do
> : do whatever with "$field3"

as long as "whatever" doesn't read from its stdin.

> done < FILENAME
>
> If it is a large file, it may be more efficient to use sed or awk
> rather than a shell loop.

That's a very good piece of advice

--
Stéphane

At 2007-07-17 11:41AM, "Ben" wrote:
> In shell, e.g. ksh,
> I have input data of the form
>
> a b c,x,c,d,
> b c x,y
>
> I'd need to process the 3rd column, how do I "explode" line by line?

If, by "explode", you mean "how do I iterate over the comma-delimited
values in the 3rd column?", then use awk:

awk '{
print;
split($3, arr, /,/);
for (x in arr) {
print "line " NR ", value[" x "]=" arr[x]
}
}' inputdata.txt



--
Glenn Jackman
You can only be young once. But you can always be immature." -- Dave Barry

On Jul 17, 8:41 am, Ben <chinese.cent...@googlemail.com> wrote:
> In shell, e.g. ksh,
> I have input data of the form
>
> a b c,x,c,d,
> b c x,y
>
> I'd need to process the 3rd column, how do I "explode" line by line?

The 3rd col is the "c" or the 2nd "c", comma is your col delimit? Ok.

My examples are in bash. A few ideas: Try to flip the IFS var, to what
you want.
That is a single quote then comma. Add in a counter to track the col
count, etc.
foo="a b c,e,f,g,1"
echo $foo
a b c,e,f,g,1
IFS=','
for x in $foo
> do
> echo "$x"
> done
a b c
e
f
g
1
Just for fun, once the IFS is changed, try echo $foo,
echo $foo
a b c e f g 1
The commas are gone,

Or Just use cut -d,
echo $foo
a b c,e,f,g,1
echo $foo|cut -d ',' -f3
f

Just for fun to see the IFS var,
echo $IFS|od -c
0000000 \n
0000001
Or on some OS's,
echo $IFS|od -ta
0000000 nl
0000001

2 cents.....

Thank you. I used to think "explode" is a common term, it's a term for
PHP, maybe not in the UNIX world then.. thanks for all the response.

On Jul 17, 9:33 pm, Glenn Jackman <gle...@ncf.ca> wrote:
> At 2007-07-17 11:41AM, "Ben" wrote:
>
> > In shell, e.g. ksh,
> > I have input data of the form
>
> > a b c,x,c,d,
> > b c x,y
>
> > I'd need to process the 3rd column, how do I "explode" line by line?
>
> If, by "explode", you mean "how do I iterate over the comma-delimited
> values in the 3rd column?", then use awk:
>
> awk '{
> print;
> split($3, arr, /,/);
> for (x in arr) {
> print "line " NR ", value[" x "]=" arr[x]
> }
> }' inputdata.txt
>
> --
> Glenn Jackman
> You can only be young once. But you can always be immature." -- Dave Barry