Как сохранить вывод mplayer в файл?

echo '123-321-333-111-235' |
awk -F'-' -v n=3 '
  {
     for( i=1; i<=n; ++i )
        k = k (k == "" ? "" : FS) $i
     ;
     print k
  }
'

Цикл for выполняется 3 раза:

i = 1:

 k is empty, $i -> $1 -> 123

 k <= empty ( empty == empty ? empty : "-" ) 123

 k <= empty empty 123

 k <= "123"

i = 2:

 k is "123", $i -> $2 -> 321

 k <= "123" ( 123 == empty ? empty : "-" ) 321

 k <= "123" "-" "321"

 k <= "123-321" due to the implicit concatenation property of awk strings

i = 3:

 k is "123-321", $i -> $3 -> 333

 k <= "123-321" ( 123-321 == empty ? empty : "-" ) 333

 k <= "123-321" "-" "333"

 k <= "123-321-333"

 This value of k is now sent to stdout.
 STOP.

В качестве альтернативы вы также можете сделать следующее:

n=3

echo '123-321-333-111-235' | sed -ne "s/-/\n/$n;P"

echo '123-321-333-111-235' | perl -F- -lane "\$, = '-'; print @F[0..$n-1]"

( 
   var='123-321-333-111-235'
   set -f; IFS='-'; set -- $var

   for((i=1;i<=$n;i++))
   do
      v=${v-}${v:+"$IFS"}$1
   done
   echo "$v"

   # or, alternatively:
   N=$#
   while case $# in `expr $N - $n` ) break ;; esac; do
     V=${V-}${V:+"$IFS"}$1
     shift
   done
   echo "$V"
)

var='123-321-333-111-235'
FS='-'; # field separator provided here
fields=$(yes "[^$FS]*$FS" | head -n $n | tr -d '\n')
result=`expr "$var$FS" : "\($fields\)"`
echo "${result%?}"