ファイル内の行を昇順に並べ替える

#!/bin/sh
#sortup.sh

. f_askfname.sh
. f_askstring.sh

ask_filename "Target File( Blank is Cancel. ): " 1
if [ $? -ne 0 ]; then
    echo "*** Canceled."
    return 1
fi
FILE1=${_STR}
echo "Target File is \"${FILE1}\""

ask_string "Save File [${FILE1}.up] : " 1
if [ $? -ne 0 ]; then
    FILE2="${FILE1}.up"
else
    FILE2=${_STR}
fi
echo "Save File is \"${FILE2}\""

sort -o ${FILE2} ${FILE1}
#降順
#sort -r -o ${FILE2} ${FILE1}
echo "*** Succesful."
unset FILE1 FILE2 _STR

$ cat 1.txt
g
f
e
d
c
b
a

$ ./sortup.sh 
Target File( Blank is Cancel. ): 1.txt
Target File is "1.txt"
Save File [1.txt.up] : 
Save File is "1.txt.up"
*** Succesful.

$ cat 1.txt.up
a
b
c
d
e
f
g