Question

I have been asked to find a shell command that doesn’t make any system call. I have searched a lot and finally ended up here asking that is there any command in linux shell or unix that doesn’t call a system call at the back end.

Thanks.

Answer 1

Think of what a shell is, how does it run the commands.

The shell is an interpreter. Roughly speaking there is a single interpreter loop

do {
   get_next_command();
   switch(next_command){
   cmd_alias: ...
   cmd_break: ...
     ...
   }
} while (true);

Now think, which command just updates the internal structures of the shell process and which command needs to call the operating system to perform its function.