In Sec. 4.7.5, it was pointed out that on an exec call, by testing for an adequate hole before releasing the current process’ memory, a suboptimal implementation is achieved. Reprogram this algorithm to do better.

Data from Sec. 4.7.5

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When a command is typed at the terminal, the shell forks off a new process, which then executes the command requested. It would have been possible to have a single system call to do both fork and exec at once, but they were provided as two distinct calls for a very good reason: to make it easy to implement I/O redirection. When the shell forks, if standard input is redirected, the child closes standard input and then opens the new standard input before executing the com- mand. In this way the newly started process inherits the redirected standard input. Standard output is handled the same way. Exec is the most complex system call in MINIX 3. It must replace the current memory image with a new one, including setting up a new stack. The new image must be a binary executable file, of course. An executable file may also be a script that must be interpreted by another program, such as the shell or perl. In that case the file whose image must be placed in memory is the binary of the interpreter, with the name of the script as an argument. In this section we discuss