根据行号合并两个文件，其中第一个文件中的行优先

Question

I'm on Unix and I need to replace lines in a file.

I have this file

1:F
3:M
5:Z
7:Q

And I need to replace lines before the : to this file

1:A
2:B
3:C
4:D
5:E
6:F
7:G
8:H
9:I
10:J
11:K
12:L

The final result should look like this

1:F
2:B
3:M
4:D
5:Z
6:F
7:Q
8:H
9:I
10:J
11:K
12:L

How can I do that?

Answer 1

You can use this awk command:

awk -F: 'FNR==NR{a[$1]=$2; next} $1 in a{$0 = $1 FS a[$1]} 1' file1 file2

1:F
2:B
3:M
4:D
5:Z
6:F
7:Q
8:H
9:I
10:J
11:K
12:L

Do read about awk here: Effective AWK Programming

Answer 2

If the lines in the short file are in the order in which they have to go into the longer file, you can use join and cut :

$ join --nocheck-order -a 2 -t ':' file1 file2 | cut -d ':' -f 1,2
1:F
2:B
3:M
4:D
5:Z
6:F
7:Q
8:H
9:I
10:J
11:K
12:L

--nocheck-order makes join ignore that the input files aren't lexically, sorted; -a 2 prints also non-matching lines from the longer file ( file2 ); -t ':' sets the delimiter to a colon. The output of just the join command is

1:F:A
2:B
3:M:C
4:D
5:Z:E
6:F
7:Q:G
8:H
9:I
10:J
11:K
12:L

and with cut , we get the first two colon separated columns of this.