Shell Programming and Scripting

data_1.txt
data_2.txt
data_3.txt
data_4.txt
data_5.txt
data_6.txt
data_7.txt
data_8.txt
.
.
data_1_2.txt
data_2_2.txt
 data_3_2.txt
 data_4_2.txt
 data_5_2.txt
  data_6_2.txt
  .

for f in *.txt
do
./progran_name $f > $f.out
done

for f in *.txt
do
./progran_name $f > $f.out &
done

for f1 f2 f3 f4 in *.txt; do
  ./prog $f1 > $f1.out &
  ...
  ./prog $f4 > $f4.out &
  wait
done

line 1: syntax error near unexpected token `f2'

data_1.txt
data_2.txt
data_3.txt
data_4.txt

for f1 f2 f3 f4 in *.txt; do
  ./prog $f1 > $f1.out &
  ./prog $f2 > $f2.out &
  ./prog $f3 > $f3.out &
  ./prog $f4 > $f4.out &
  wait
done

for f in *.txt; do
 ./prog $f > $f.out & 
 wait
done