shell编程：实现shell字符串连接功能

功能：实现shell字符串连接功能

a=0
s1=test.
s2=.wav
s3=.mp3
s4=0
s5=00
 
str="sox ./${s1}${a}${s2} ./${a}${s3}"
 ./tts -c bcgirl.0.0.4.bin -b 1 -i input.txt -s 1.0 -speed 1.0
$str
rm ./*.wav