field replacement

Shell Programming and Scripting
1

Hi,

I have a CSV file with around 1000 rows (lines) and 1000 columns (fields).
I need to replace mth lines's nth field with a value. (E.g., 400th field of 300th line). how can i do that?

Pl advise.

Thanks
Prvn

2

what have you tried?

3

I tried extracting the fields other than to be replaced. Using "echo" i could again write to another file with new value.

It worked but looked very inefficient. i guess it can be easily achieved with "awk". Pl advise.

Prvn

4

show your code.

5

get the input from the user like lineno and columnno the rest is done by this awk

 
awk -F"," -v var1=$lineno -v var2=$columnno 'NR == var1{gsub(var2,"value")}{print $0}' filename
6

Actually you could simply do

awk -F, -v line=$m -v col=$n 'NR == line { $col="value" }1' filename
7

Thanks Vidhyadhar and era.

Era - when i used your solution, replacement done but "," also vanished.

#cat /tmp/test
1,2,3
4,5,6
7,8,9
#gawk -F, -v line="2" -v col="2" 'NR == line { $col="value" }1' /tmp/test
1,2,3
4 value 6
7,8,9
#

Vidhyadhar - when i ran your solution, o/p remains as acutal file contents (no replacements done).

Thanks
Prvn

8

Adding -v OFS=, seems to fix that for me, on mawk.

9

Try adding the OFS to era's solution:

gawk -F, -vl=2 -vc=2 -vOFS=, '(NR==l&&$c="newone")||1' filename
10

Thanks era and Radoulov, your solution working fine.

#cat /tmp/test
1,2,3
4,5,6
7,8,9
#newone="RPK"
#gawk -F, -vl=2 -vc=2 -vOFS=, -vval=$newone '(NR==l&&$c=val)||1' /tmp/test
1,2,3
4,RPK,6
7,8,9
#

Thanks again!