How to print the length size of the following line - awk

Question

I would like to modify a file by including the size of following line using awk.
My file is like this:
>AAAS:1220136:1220159:-:0::NW_015494524.1:1220136-1220159(-)
ATGTCGATGCTCGATC
>AAAS::1215902:1215986:-:1::NW_015494524.1:1215902-1215986(-)
ATGCGATGCTAGCTAGCTCGAT
>AAAS:1215614:1215701:-:1::NW_015494524.1:1215614-1215701(-)
ATGCCGCGACGCAGCACCCGACGCGCAG
I am using awk to modify it to have the following format:
>Assembly_AAAS_1_16
ATGTCGATGCTCGATC
>Assembly_AAAS_2_22
ATGCGATGCTAGCTAGCTCGAT
>Assembly_AAAS_3_28
ATGCCGCGACGCAGCACCCGACGCGCAG
I have used awk to modify the first part.
awk -F":" -v i=1 '/>/{print ">Assembly_" $1 "_" val i "_";i++;next} {print length($0)} 1' infile | sed -e "s/_>/_/g" > outfile
I can use print length($0) but how to print it in the same line?
Thanks

Answer 1

EDIT2: Since OP has changed the sample data again so adding this code now.
awk -v val="Assembly_AAAS_" '/>/{++i;val=">"val i "_";next} {sub(/ +$/,"");print val length($0) ORS $0}' Input_file
OR
awk -v val="Assembly_AAAS_" '/>/{++i;val=">"val i "_";next} {print val length($1) ORS $0;}' Input_file
Above will remove spaces from last of the lines of Input_file, in case you don't need it then remove sub(/ +$/,""); part from above code please.
EDIT: As per OP changed solution now.
awk -v i=1 -v val=">Assembly_GeneName1_" -v val1="_sizeline" '/>/{value="\047" val i val1;i++;next} {print value length($0) ORS $0}' Input_file
OR
awk -v i=1 -v val=">Assembly_GeneName1_" -v val1="_sizeline" '
/>/{ value="\047" val i val1;
i++;
next}
{
print value length($0) ORS $0
}
' Input_file
Following awk may help you on same.
awk -v i="" -v j=2 '/>/{print "\047>Assembly_GeneName1_"++i"_sizeline"j;j+=2;next} 1' Input_file
Solution 2nd:
awk -v i=1 -v j=2 -v val=">Assembly_GeneName1_" -v val1="_sizeline" '/>/{print "\047" val i val1 j;j+=2;i++;next} 1' Input_file

Answer 2

What you are dealing with is a beautiful example of records which are not lines. awk is a record parser and by default, a record is defined to be a line. With awk you can define a record to be a block of text using the record separator RS.
RS : The first character of the string value of RS shall be the input record separator; a <newline> by default. If RS contains more
than one character, the results are unspecified. If RS is null, then
records are separated by sequences consisting of a <newline> plus one
or more blank lines, leading or trailing blank lines shall not result
in empty records at the beginning or end of the input, and a <newline>
shall always be a field separator, no matter what the value of FS is.
So the goal is to define the record to be
AAAS:1220136:1220159:-:0::NW_015494524.1:1220136-1220159(-)
ATGTCGATGCTCGATC
And this can be done by defining the RS="\n<". Furthremore we will use \n as a field separator FS. This way you can get the requested length as length($2) and the count by using the record count NR.
A simple awk script is then:
awk 'BEGIN{RS="\n<"; FS=OFS="\n"}
{$1=">Assembly_AAAS_"NR"_"length($2)}
{print $1,$2}' <file>
This will do exactly what you want.
note: we use print $1,$2 and not print $0 as the last record might have 3 fields (if the last char of the file is a newline). This would imply that you would have an extra empty line at the end of your file.
If you want to pick the AAAS string out of $1 you can use substr($1,1,match($1,":")-1) to pick it up. This results in this:
awk 'BEGIN{RS="\n<"; FS=OFS="\n"}
{$1=">Assembly_"substr($1,1,match($1,":")-1)"_"NR"_"length($2)}
{print $1,$2}' <file>
Finally, be aware that the above solution only works if there are no spaces in $2, if you want to change that, you can do this :
awk 'BEGIN{RS="\n<"; FS=OFS="\n"}
{ gsub(/[[:blank:]]/,"",$2);
$1=">Assembly_"substr($1,1,match($1,":")-1)"_"NR"_"length($2)
}
{ print $1,$2 }' <file>