unix - head AND tail of file

You can simply:

(head; tail) < file.txt

And if you need to uses pipes for some reason then like this:

cat file.txt | (head; tail)

Note: will print duplicated lines if number of lines in file.txt is smaller than default lines of head + default lines of tail.

For a pure stream (e.g. output from a command), you can use 'tee' to fork the stream and send one stream to head and one to tail. This requires using either the '>( list )' feature of bash (+ /dev/fd/N):

( COMMAND | tee /dev/fd/3 | head ) 3> >( tail )

or using /dev/fd/N (or /dev/stderr) plus subshells with complicated redirection:

( ( seq 1 100 | tee /dev/fd/2 | head 1>&3 ) 2>&1 | tail ) 3>&1
( ( seq 1 100 | tee /dev/stderr | head 1>&3 ) 2>&1 | tail ) 3>&1

(Neither of these will work in csh or tcsh.)

For something with a little better control, you can use this perl command:

COMMAND | perl -e 'my $size = 10; my @buf = (); while (<>) { print if $. <= $size; push(@buf, $_); if ( @buf > $size ) { shift(@buf); } } print "------\n"; print @buf;'

ed is the standard text editor

$ echo -e '1+10,$-10d\n%p' | ed -s file.txt