split a file based upon line number - bash

Question

I have a large file that needs to be slitted based on line numbers.
For instance , my file is like that:
aaaaaa
bbbbbb
cccccc
dddddd
****** //here blank line//
eeeeee
ffffff
gggggg
hhhhhh
*******//here blank line//
ıııııı
jjjjjj
kkkkkk
llllll
******
//And so on...
I need two separate files as such that one file should have first 4 lines, third 4 lines, fifth 4 lines in it and the other file should have second 4 lines, fourth 4 lines, sixth 4 lines in it and so on. how can I do that in bash script?

Answer 1

You can play with the number of the line, NR:
$ awk 'NR%10>0 && NR%10<5' your_file > file1
$ awk 'NR%10>5' your_file > file2
If it is 10K + n, 0 < n < 5, then goes to the first file.
If it is 10K + n, n > 5, then goes to the second file.
In one line:
$ awk 'NR%10>0 && NR%10<5 {print > "file1"} NR%10>5 {print > "file2"}' file
Test
$ cat a
1
2
3
4
6
7
8
9
11
12
13
14
16
17
18
19
21
22
23
24
26
27
28
29
31
32
33
34
36
37
38
39
41
42
43
44
46
47
48
49
51
$ awk 'NR%10>0 && NR%10<5 {print > "file1"} NR%10>5 {print > "file2"}' a
$ cat file1
1
2
3
4
11
12
13
14
21
22
23
24
31
32
33
34
41
42
43
44
51
$ cat file2
6
7
8
9
16
17
18
19
26
27
28
29
36
37
38
39
46
47
48
49

Answer 2

You can do this with head and tail (which are not be part of the bash itself):
head -n 20 <file> | tail -n 5
gives you the lines 15 to 20.
This is however inefficient, if you want to get multiple sections of your file, since it has to be parsed again and again. In this case I'd prefer some real scripting.

Answer 3

Another approach is to treat blank-line-separated paragraphs as the records, and print odd-numbered and even-numbered records to different files:
awk -v RS= -v ORS='\n\n' '{
outfile = (NR % 2 == 1) ? "file1" : "file2"
print > outfile
}' file

Answer 4

Maybe something like that:
#!/bin/bash
EVEN="even.log"
ODD="odd.log"
line_count=0
block_count=0
while read line
do
# ignore blank lines
if [ ! -z "$line" ]; then
if [ $(( $block_count % 2 )) -eq 0 ]; then
# even
echo "$line" >> "$EVEN"
else
# odd
echo "$line" >> "$ODD"
fi
line_count=$[$line_count +1]
if [ "$line_count" -eq "4" ]; then
block_count=$[$block_count +1]
line_count=0
fi
fi
done < "$1"
The first argument is the source file: ./split.sh split_input

Answer 5

This script prints lines from file 1.txt with indexes 0, 1, 2, 3, 8, 9, 10, 11, 16, 17, 18, 19, ...
i=0
while read p; do
if [ $i%8 -lt 4 ]
then
echo $p
fi
let i=$i+1
done < 1.txt
This script prints lines with indexes 4, 5, 6, 7, 12, 13, 14, 15, ...
i=0
while read p; do
if [ $i%8 -gt 3 ]
then
echo $p
fi
let i=$i+1
done < 1.txt