4w ago

How can I use line continuations in GNU awk?

For a reason not worth mentioning here, I would like to write a somewhat more complex awk script in which I would have to explain in detail what I am doing. (If only so that I'll still know next week.) There doesn't seem to be a way to wrap a list of conditions in GNU awk, right?

This is what I tried:

 shell

    
command-that-prints-a-table | awk '
    NR>1 &&                # Skip line 1
    NF>2 &&                # Skip lines with only one column
    substr($1,1,1) != "("  # Skip lines that start with a "("
    { print $1 }
'

Alas, that does not work - awk skips the conditions entirely and only runs print $1. It seems that escaping the newlines does not work either, which makes sense as the end of the lines are comments.

This would work:

 shell

    
command-that-prints-a-table | awk '
# - Skip line 1
# - Skip lines with only one column
# - Skip lines that start with a "("
    NR>1 && NF>2 && substr($1,1,1) != "("  { print $1 }
'

But - my original code has a few more conditions - it is rather annoying to read and maintain. Is there an elegant way to fix this?

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10 comments

If you're talking specifically about bash-compliant shells, just use a backslash.
- Wouldn’t the backslash be a part of the comment?
  
  It a line continuation like so:
  printf "This is going to be a really \ long line that I want to break \ into different segments"
  I'm seeing references that this is supposed to work elsewhere as well.
  
  Sure, but that's inside a string:
  shell
  
  $ printf "This is a # let's break \ > long line." This is a # let's break long line.
  awk remains unimpressed:
  shell
  
  $ echo "This is a test. > It has three lines, so I can > test awk on it." | awk ' > NR>2 # Skip two lines. \ > { print $2 } # should only print "awk" > ' is has test awk on it. awk
  
  It works with long commands as well. Thinking in awk though, I would only use it after a statement is complete. You wouldn't be able to split up expressions like this, but if you're just talking about making it more readable, it should work.
  Backslash works for long commands as well, but it's not going to split up an expression or string properly.
  Works: apt install package1 \ package2 \ package3
  Won't work: apt install pack\ age1 package2 pack\ age3
  You can get cleaner code by substituting content blocks as variables, or piping EOF in and out at various places as other options.
  
  You wouldn’t be able to split up expressions like this
  Ah, that already answers my original question. A pity!
  
  If cleaner is all you want, and you don't specifically care about the tool, maybe look at pyp
  
  Ah, I could probably use Perl or something as well. I was hoping awk could do it though. But thank you, I hadn't heard about pyp before!

10 comments