(I'm not sure if it's a appropriate question here)

Shell script, like bash, can do many things. It can call Unix programs, pipe their output, redirect I/O from/to files, control flow, check whether a file exists, etc.

But a modern programming language, e.g, python and ruby, can also do these all. And their are (I think) more readable and maintainable.

bash is worldwide spreaded. But many distributions have installed python interpreter, too.

So what's the advantage of shell script? If I could write python, ruby or perl, is it worth to learn bash?