That's the way current shells work. They do actually use buffered input, but they use lseek on the input so each time they always read the next command from th

That's the way current shells work. They do actually use buffered input, but they use lseek on the input so each time they always read the next command from the file. You can prove this fairly easily: $ cat input.sh echo hello sleep 10 echo world During the sleep, edit input.sh and change "world" to something else. It will print the something else. It should be possible to implement goto etc as external commands, although of course somewhat inefficient and unnecessary.