awk command with pipe lining some doubts - linux

Question

I know in the below code the pipe command will pass the output to next command. But I have a doubt in the case of awk execution. My doubt is that
Is each awk block will iterate through all the lines in the file or it will iterate one by one through the line. More clearly and as I assumed ...
1) 1st awk block will iterate through 1st line.
2) print that line if condition satisfies. (pass this out put to next awk block)
3) else do nothing
4) next awk block recieves this output and process that particular line.
5) write it in the filereceipt.tmp
In this way it processing or
1) 1st awk block will iterate through all the lines in that file.
2) pass the out put to next awk block
3) next awk block will operate up on the out put passed 1st awk block.
Please help me. I have no option torun this commands. Thanks in advance!
cat > /tmp/pay.dat
grep -v '^TRAILER' /tmp/pay.dat
| \
awk '{
if ((substr($0,145,2) != "CA")
{
print $0
}
}'
|\
awk 'BEGIN{OFS=""} \
{
if (substr($0,38,1) == "X") \
{
print substr($0,1,37), "S", substr($0,39)
} \
else {
print $0
}
}' > /tmp/receipt.tmp

Answer 1

Either and/or both.
What? How?
Each awk will iterate over the lines given to it - the first awk receives lines that don't start with "TRAILER", the second receives the lines that the first gives to it. The processes execute in parallel, each reading and writing data as it pleases. (A process that tries to read data that has not yet been written will sleep until that data is available.)
The order in which any side effects happen is unpredictable, depending on system process scheduling (including current load), pipe buffer sizes, awk execution overhead, etc.
Shellscript formatting
The grep and the first awk are on their own lines, which do not end in pipes or backslashes. That's not a pipeline, it's just a bunch of commands. And if you're using the Bourne shell or any shell descended from it, quoted strings don't need backslashes - they continue until interrupted by a closing quote.
Try something like this:
# This assumes that your data is already in "/tmp/pay.dat".
grep -v "^TRAILER" /tmp/pay.dat |
awk 'your first
awk script' |
awk 'your second
awk script' > /tmp/receipt.tmp
(In a Bourne-derived shell, lines ending in | are automatically continued - no trailing backslash required.)