Any solution to get previous line in awk

Shell Programming and Scripting
1

Hi all...

Is there any solution to do the reverse process of getline ?

Thanks in advance.

2

Why not only save line to variable ?

{ 
  # save current line for later using
   prev=$0
}

If need previous line, you can use variable or return it to the variable $0

{ # some rule
     # save current for later using
     curr=$0
     # take previous line
     $0=prev
     # do something
     ...
     # and return current line
     $0=curr
}
3

Thanks a lot...

4

Prints line before pattern

awk '/pattern/ {print a}{a=$0}'
5

Hi Jotne,

Could you please explain the code?

Thanks!

6 
awk '
	/pattern/ {print a}
	{a=$0}'

Running on a file:
Line1: Does it contain "pattern", yes print a (here a will be empty), no continue
a=Line1
Line2: Does it contain "pattern", yes print a (her a contial line1), no continue
a=Line2
Line3: Does it contain "pattern", yes print a (her a contial line2), no continue
a=Line3

So a does always contain previous line.

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