Pipe output of one command to two others [duplicate]

Question

I need to pipe the output of one command to two other commands.

cat filename.txt | tail -n 1
cat filename.txt | wc -l

Since the file is huge I want to avoid reading it twice. I checked tee command but it redirects output to file which I don't want. There are many related posts but did not find anything relevant

Answer 1

If I understood correctly, you want to get the last line of the file along with the line count:

$ cat a
aaa
bb
ccc
$
$ awk 'END{print $0; print NR}' a
ccc
3

Since you need them to save in variables:

$ out=$(awk 'END{print $0"|"NR}' a)
$ last_line=$(echo $out | awk -F"|" '{print $1}' )
$ tot_cnt=$(echo $out | awk -F"|" '{print $2}' )
$ echo $last_line
ccc
$ echo $tot_cnt
3

Answer 2

{   
    {   tee /dev/fd/3 | wc -l >&4
    }   3>&1 | tail -n1
}   <filename.txt 4>&1

It doesn't avoid reading it twice - but on multicore systems it will likely be concurrent. The output order is in no way guaranteed, however.

Probably the fastest way to simulate what you're asking for, though, is:

dd bs=64k <filename.txt | tail -n1

dd will report its read/writes to stderr and still copy all of the file to stdout.

Answer 3

Let the cat sleep, you don't need it.

Use :

tail -n 1 filename.txt
wc -l filename.txt