Shell Programming and Scripting

Hi,

I would like to perform bash which would check the file A.txt to be size 0 or not. If the size is 0, I would copy file B.txt to replace A.txt.

Please help.

Thanks.


-Jason

look into 'man test'

Thanks.

But if i would like to add in a third field with 0 of the intended copied file; how could I do so without creating another files.

Means :-

in MM folder I have A.txt(size which is 0) and in NN folder I have similar A.txt (size more than 0)

if [-s MM/A.txt] then

else cat NN/A.txt <perform the addition of all 0s in third field of A.txt>
copy MM/A.txt to NN/A.txt

I would like to perform the substitution if the size is 0 before copied to the new path.


Thanks.

-Jason

It's easier to read if you use 'CODE' tages around code:
So NN/A.txt contains some 0's in the third field, and you want to add then up? <confused>
Or do you want to add them to MM/A.txt? Even though it's currently blank? <still confused>

Please show an example of what you are trying to do.

Also, consider using [ ! -s ] so you don't need the 'else' section in your code.

Hi,

Please disregard the previous said problem as I think I was quite confused by that time.

More clearer picture is below:-

Let us consider we have two files; A.txt and B.txt.

First, I would check the A.txt; if the A.txt is zero size; i would like to copy B.txt content to A.txt but changing all the second field of B.txt content to 0.

Given B.txt input is

1 2
2 3
3 4
1 5
1 6

And output of A.txt would be

1 0
2 0
3 0
1 0
1 0

Currently, I am thinking to use the

if [!- s A.txt]
paste B.txt |awk '{$2=0}' >> A.txt

But it does not work. Please advise. THanks.

-Jason

Remember to use 'CODE' tags

You need a 'then' clause in your if statement and to end it with a 'fi'

I don't see a reason to use paste,
just use awk to grab the first column:

Code:

awk '{ print $1,"0" }' < B.txt > A.txt

Code:

if [ ! -s "file" ];then
    while read one two
    do
        echo "$one 0" >> A.txt
    done < B.txt
fi