Add blank line between lines from different groups

问题

I have a file A of the form (frequency,file name,code lines):

1 file_name1 code_line1
2 file_name2 code_line2
2 file_name2 code_line3
2 file_name3 code_line4
2 file_name3 code_line5
3 file_name4 code_line6
3 file_name4 code_line7
3 file_name4 code_line8

I want output B as:

1 file_name1 code_line1

2 file_name2 code_line2
2 file_name2 code_line3

2 file_name3 code_line4
2 file_name3 code_line5

3 file_name4 code_line6
3 file_name4 code_line7
3 file_name4 code_line8

Basically the file A contains file name and code lines from the file and the first field is the frequency, i.e., number of code lines in the file.

I am supposed to go through these code lines file wise. I am finding it tedious and it would be easier for me if there was a line gap between entries of different files, hence the desired output.

回答1:

Awk could do it:

awk '{if(NR > 1 && $2 != prev_two){printf "\n";} prev_two=$2; print $0}' A

A being the file name.

回答2:

You can use Awk:

awk 'BEGIN{file=0}{if (file && file!=$2) {print ""} print $0; file=$2}' fileA

回答3:

Quick and dirty Perl for you:

$lastfile = '';
while (<>) {
  @line = split(/\s+/);
  $filename = $line[1];
  print "\n" unless ($lastfile eq $filename);
  $lastfile = $filename;
  print;
}

Usage: perl script.pl < original_file.txt > newfile.txt

回答4:

To add to the awk and Perl solutions, a GNU sed solution:

$ sed -r 'N;/file_name(\w+).*\n.*file_name\1/!{s/\n/&\n/;P;s/^[^\n]*\n//};P;D' infile
1 file_name1 code_line1

2 file_name2 code_line2
2 file_name2 code_line3

2 file_name3 code_line4
2 file_name3 code_line5

3 file_name4 code_line6
3 file_name4 code_line7
3 file_name4 code_line8

Explained:

N # Append next line to pattern space

# If the numbers after the 'file_name' string DON'T match, then
/file_name(\w+).*\n.*file_name\1/! {
    s/\n/&\n/      # Insert extra newline
    P              # Print up to first newline
    s/^[^\n]*\n//  # Remove first line in pattern space
}
P # Print up to newline - if we added the extra newline, this prints the empty line
D # Delete up to newline, start new cycle

来源：https://stackoverflow.com/questions/4380447/add-blank-line-between-lines-from-different-groups

标签

Linux

shell

scripting

sed

awk