woqunokia

I use the example support by yours.

Thank you, I tried. but when modify by "echo "bb" >> test.txt" (it's append in the end of file ) like this, it's print once, but if i use "bb"...

I use an edition maybe print more. could you explain the different between "echo "bb" > test.txt" and "echo "bb" >> test.txt" . thanks.

I konw "echo "bb" >> test.txt" , clean the file then write,but after clean it don't save the file.