Substitution of a line with another line in multiple files

Question

I have to substitute the content of lines from a file with another line (in the same position number 3) in multiple files. The problem looks like the following:

Input1

file.list <- list("a","b","c","d")
file.list <- list("d","e","f","g")
file.list <- list("h","i","l","m")

Input2.file

library(data.table)
library(dplyr)
file.list <- list("z","g","h","s","i")

Input3.file

library(data.table)
library(dplyr)
file.list <- list("s","p","q","r","m")

Input4.file

library(data.table)
library(dplyr)
file.list <- list("x","k","s","e")

Output of Input2.file

library(data.table)
library(dplyr)
file.list <- list("a","b","c","d")

Output of Input3.file

library(data.table)
library(dplyr)
file.list <- list("d","e","f","g")

Output of Input4.file

library(data.table)
library(dplyr)
file.list <- list("h","i","l","m")

I have tried to do as follow:

filename='Input1'
for i in *.file; do #here i loop over the list of files
    while read p $filename; do #here i loop over the lines of Input1 file
        awk '{ if (NR == 3) print "$p"; else print $0}' $i > $i.test; ##here i substitute the line 1 in the files with the line that are in Input1 file
    done;
done

Am doing something wrong because the script is stopping without giving me any message. What am doing wrong? Any Idea?

Answer 1

$ gawk -i inplace '
    NR == FNR {repl[FNR] = $0; next} 
    FNR == 1  {filenum++} 
    FNR == 3  {$0 = repl[filenum]} 
    {print}
' Input1 Input{2,3,4}.file

$ cat Input2.file
library(data.table)
library(dplyr)
file.list <- list("a","b","c","d")

$ cat Input3.file
library(data.table)
library(dplyr)
file.list <- list("d","e","f","g")

$ cat Input4.file
library(data.table)
library(dplyr)
file.list <- list("h","i","l","m")

---

Looking at your code:

1. you're replacing line 3 in each *.file with every line of Input1. You'll be left with the last line of Input1 as line 3 for every *.file.
2. $p cannot be expanded in your awk script, because it's in single quotes.

Try this:

exec 3<Input1   # set up file descriptor 3 to read from Input1 file
for f in *.file; do
    read -r -u 3 replacement   # read a line from fd 3  
    awk -v rep="$replacement" '{if (NR == 3) print rep; else print $0}' "$f" > "$f.test"
done
exec 3<&-       # close fd 3

Answer 2

to substitute the content of lines from a file with another line

bash + sed solution:

i=0; for f in Input[2-4].file; do ((i++)); sed -n "${i}p" "Input1" > "$f"; done

---

Viewing results:

$ head Input[2-4].file
==> Input2.file <==
file.list <- list("a","b","c","d")

==> Input3.file <==
file.list <- list("d","e","f","g")

==> Input4.file <==
file.list <- list("h","i","l","m")