Awk matching of entire record using regular expression

Question

Using Awk I want to match the entire record using a regular expression. By default the regular expression matching is for parts of a record.

The ideal solution would:

• Be general for all fields, regardless of the field separator used.
• Not treat the entire input as a single field and parse it manually using string functions.
• Work in a general way and not be specific to gawk for example.

However any and all solutions are of interest as long as they use Awk without calls to external programs.

An example, I have:

$ ls
indata.txt  t1.awk
$ cat indata.txt 
a1010_
1010_
1010_b
$ cat t1.awk 
/[01]*_[01]*/ { print $0 }

I get:

$ awk -f t1.awk indata.txt
a1010_
1010_
1010_b

This is the result I am seeking:

$ awk -f t1.awk indata.txt
1010_

Answer 1

You just need to add a beginning and end anchor to your regex:

/^[01]*_[01]*$/ { print $0 }

Answer 2

$ gawk '/^[01]*_[01]*$/' indata.txt
1010_