extract particular lines from text file

Shell Programming and Scripting
1

I have two files

file A which have a number in every row and file B which contains few hundred thousand rows with about 300 characters in each row (csv)

What I need is to extract whole rows from B file (only these which numbers are indicated in A file)

I also need to use cygwin.

Any help will be appreciated.

2

It will be good if you show a sample input and desired output???

3 
A file input:

3
4
6
8
10


B file input 
aaa|sdftqwtegaerta|Adfgadfhgsa
bbb|asdgfasdgart|fghsdfhsdfhs
ccc|dag5dsgarf|fhsdfh7
ddd|da4dsgarf|fhsdfhsdhf
eee|dagsdgadsgarf|fhsdfhsdhf
fff|dags3sgarf|fhsdfhsdy
ggg|dagsdgadsgarf|fhsdfhsdhf
hhh|dags345gadsgarf|fhsdrf
jjj|dagsdgadsgarf|fhsdfh34
kkk|dagsdgadsgarf|fhs354
lll|dagsdgadsgarf|fhsd54

desired output
ccc|dag5dsgarf|fhsdfh7
ddd|da4dsgarf|fhsdfhsdhf
fff|dags3sgarf|fhsdfhsdy
hhh|dags345gadsgarf|fhsdrf
kkk|dagsdgadsgarf|fhs354
4

Try...

 
awk -F"|" 'NR==FNR{arr[FNR]=$0;next}{for(i in arr)if(i==$1)print arr}' fileB fileA
5

A sed version :

for i in `cat file1.txt`
do
sed -n "$i p" file2.txt >> op.txt
done
6

thx, awk version works fine for me

7

This is an alternative if you have more file than memory can hold. This only holds the indexes in memory instead of the data file...

awk 'NR==FNR{arr[$1]=0;next} (FNR in arr){print $0}' fileA fileB
8

What if I wanted to remove those lines from the original file at the same time?