Set number of lines to variable in awk - awk

Question

I am experimenting with an awk script (an independent file).
I want it to process a text file which looks like this:
value1: n
value2: n
value3: n
value4: n
value5: n
value6: n
value7: n
value1: n
:
The text file contains a lot of these blocks with 7 values in each of them. I want the awk script to print some of these values (name of the value and "n") into a new file or the commandline. I thought I'd process it with a while loop, which works with a variable set to the number of all lines. But I just cant get the total of all lines in the file into a variable. It seems I have to process every line and do something with it until the end of the file to get the total. But I'd like to have the total in a variable and then process it with the while loop which loops until the total is reached.
Do you have an idea?

Answer 1

Where $1 is the input parameter to your script: myscript textfile.txt
count="`wc -l $1 | cut -d' ' -f1`"
echo "Number of lines in $1 is $count"
Then do your awk command utilising $count as your line count
Edit: courtesy of fedorqui
count="`wc -l <$1`"
echo "Number of lines in $1 is $count"
Edit 2: (forgive my awk command it's not something that I use much)
count="`wc -l </etc/fstab`"
echo "Number of lines in /etc/fstab is $count"
awk '{print $0,"\t","\tLine ",NR," of ","'$count'";}' /etc/fstab

Answer 2

Either do two passes over the file:
awk 'NR==FNR { lines = NR; next }
{ ... this happens on the second pass, use lines as you wish ... }' file file
or read the lines into an array and process it in END:
awk '{ a[NR] = $0 }
END { lines = NR; for(i=1; i<=lines; ++i) { line = a[i]; ... } }' file
The first consumes I/O, the second memory.
In more detail,
awk 'NR==FNR { count++; next }
{ print "Item " FNR " of " count ": " $0 }' file file
or similarly
awk '{ a[NR] = $0; }
END { for (i=1; i<=NR; ++i) print "Item " i " of " NR ": " a[i] }' file
If you need the line count outside of Awk, you will need to print it and capture it from your script. If you have an Awk script which performs something useful and produces the count as a side effect, you will want to print the line count to standard output, and take care that all other output is directed somewhere else. Perhaps like this;
lines=$(awk '{ sum += $1; }
END { print "Average: " sum/NR >"average.txt"; print NR }')
# Back in Bash
echo "Total of $lines processed, output in average.txt"