Shell Programming and Scripting

Hi All,
I have problem to solve
aaaa,aaaaa,aaa,aaaa,aaa,aa ,aa
bbbb,bbbbbbbbb,bbbb,bbbbb ,bb

to
aaaa;aaaaa,aaa ;aaaa;aaa,aa ;aa
bbbb;bbbbbbbbb;bbbb;bbbbb ;bb

i try use sed to find and replace, but dont know how to replace specific column position.

can u help me??

thx for the comment.

echo "aaaa;aaaaa;aaa ;aaaa;aaa;aa ;aa"|awk -F ";" '{$2="bbbbbbbb"; printf "%s;%s;%s;%s;%s\n", $1,$2,$3,$4,$5}'

awk -F sets the delimiter for columns and then each column is represented by $1 $2 $3 $4 $5. Change them as you see fit.

what i'm concern is, replace all commas delimiter to semicolon except several column
e.g
i have a file contains two lines:
aaaa,aaa,aa,aaaa,aaaa aa
cccc,ccccc ,cccc,cccc,cc

and i want change it into
aaaa;aaa,aa;aaaa;aaaa aa
cccc;ccccc ;cccc;cccc,cc

*sorry my english not well enough

echo "aaaa,aaa,aa,aaaa,aaaa aa"|sed -e 's/a/c/g' | awk -F "," '{printf "%s;%s%s;%s;%s,%s\n", $1,$2,$3,$4,substr($5,0,4),substr($5,6,2)}'

I hope you can understand the code. Like I said with the code I already had gave you it was possible to change any field with appropriate tweaking.

not change the 'a' letter to 'c' like u mention above,.
and i modify to
echo "aaaa,aaa,aa,aaaa,aaaa aa" | awk -F "," '{printf "%s;%s%s;%s;%s,%s\n", $1,$2,$3,$4,substr($5,0,4),substr($5,6,2)}'

from ur code, it will
change
aaaa,aaa,aa,aaaa,aaaa aa
into
aaaa;aaaaa;aaaa;aaaa,aa

the result line length reduced,... it should be
aaaa;aaa,aa;aaaa;aaaa aa

Just add a space in printf format strings:

echo "aaaa,aaa,aa,aaaa,aaaa aa" | awk -F "," '{printf "%s;%s%s ;%s;%s,%s\n", $1,$2,$3,$4,substr($5,0,4),substr($5,6,2)}'

in my input sample
aaaa,aaa,aa,aaaa,aaaa aa

i just want to change commas in position 5,12,17 into semicolon..
no change in data

i try to make an array and make a script, see below

set -A dlm -- 5 12 17
echo ${#dlm[*]}
inc=0
echo "cat FILENAME | sed \ " > ascript
while [ $inc -lt ${#dlm[*]} ] ; do
cmd=" -e '/^\(.\{${dlm[$inc]}\}\),\(.*\)/ s//\1\;\2/g' \ "
echo $cmd >> ascript
let inc=inc+1
done
chmod 775 ascript
ascript


but still problem occurs,
is there somtin wrong with my script ??