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sed - use back reference in 2nd command

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# 8  
Old 08-08-2017
hold space vs. back reference
Quote:
Originally Posted by bakunin
What you need is not a (non-persistent) backreference but the (persistent) "hold space": this is a space where you can add, copy or pull text out of. I suggest you read the man page of sed to make yourself acquainted with the concept.

You best start by thinking through what you need to do for every type of line, i.e.:

a) lines with "country=" in them: load hold space with country code
b) all lines:
b1) split into tags (starting with "<")
b2) remove the tags themselves (as i took it from your sample output)
b3) add the content of the hold space to the begin of the pattern space

Note that you make your life a lot easier by using multi-line sed-programs. In principle you can the above also in a one-liner - like you can write a C program into one line too - but it would be very hard to read, even harder to understand and nigh impossible to debug.

I hope this helps.

bakunin
Thanks. I'll look into that. the data comes in all on one line, which is what allowed me to think the back reference would work. I'll look at the hold space as an option.
# 9  
Old 08-09-2017
Quote:
Originally Posted by JenniferAmon
I'll look at the hold space as an option.
Here is an example on how to use the hold space. It does not exactly solve your requirement but illustrates IMHO quite well how the mechanism works:

This is your input file:

Code:
=Chapter 1
line 1
line 2
line 3
=Chapter 2
line A
line B
line C

We want the "chapter headings" to appear after every line of that chapter like this:

Code:
line 1 (Chapter 1)
line 2 (Chapter 1)
line 3 (Chapter 1)
line A (Chapter 2)
line B (Chapter 2)
line C (Chapter 2)

The following sed-script will do this. I have added comments, which are NOT part of the script, so you should remove them when you try it:

Code:
sed '/^=/ {                     # only lines starting with "=" , do:
             s/^=//             #    remove the leading equal sign
             s/^/ (/            #    add a leading " (" to the remainder
             s/$/)/             #    add a trailing ")"
             h                  #    move the result to the hold space
             d                  #    delete the line from pattern space
          }
     G                          # all lines: add content of hold space to pattern space
     s/\n// ' inputfile         # remove EOL markers from inside lines

Notice that the last line is necessary: the hold space is delimited by its own EOL marker which is copied to the pattern space too. A line in pattern space would look like:

Code:
<line content><EOL>                  # initially, after reading in the line
<line content><EOL><hold space><EOL> # after copying hold space content

and you need to get rid of the EOL in the middle so that the line when printed is not broken into two.

I hope this helps.

bakunin
# 10  
Old 08-09-2017
Quote:
Originally Posted by MadeInGermany
And another one that works like the previous suggestions.
Code:
sed 's/</\
/g' inputfile.txt | sed '
\#^Country code="\(.*\)".*#{s##\1#;h;}
\#^tag>#!d
G;s#^tag>\(.*\)\n\(.*\)#\2 \1#
'

Because the first sed splits into lines, the second sed can take any number of <tag>s. Also it will tolarate(discard) other stuff in between (for example a <b> tag).
A Countr= header is left as an exercise.
This works beautifully! Thank you. I'm going to go with this to start with, while I continue to look at and decipher the others.
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