Read Chapter 9 of TLCL.

Self Study

Review the process fork/exec diagram:

$ ./tolower

fork/exec flow

When you type the name of a command at the prompt and press <Enter>:

1. at which point in the diagram is your permission to execute the program checked?
2. what is responsible for the the check, the shell or the kernel?

and

$ ./tolower <jump.txt

fork/redirect/exec flow

When you run a command with its input or output redirected:

1. at which point in the diagram is your permission to read or write to the redirected file (in this case, permission to read ‘jump.txt’) performed?
2. what is responsible for performing the permission check, the shell or the kernel?