Andy Wang Operating Systems COP 4610 / CGS 5765 Project 1 Hints Andy Wang Operating Systems COP 4610 / CGS 5765

Overall Parsing chdir() is a system call Use calloc() instead of malloc() Use multiple passes to simply parsing One pass to create an array of string tokens One pass for input redirection One pass for output redirection chdir() is a system call

Foreground Execution fork() Shell Shell waitpid(pid, &status, 0)

Foreground Execution fork() Shell Shell execvp(bin_path, argv) waitpid(pid, &status, 0)

Foreground Execution fork() Shell Shell waitpid(pid, &status, 0)

Background Execution fork() Shell Shell waitpid(-1, &status, WNOHANG)

Background Execution fork() Shell Shell execvp(bin_path, argv) waitpid(-1, &status, WNOHANG)

Background Execution fork() Shell Shell waitpid(-1, &status, WNOHANG)

Input Redirection shell file descriptors 0 stdin 1 stdout 2 stderr fork() file descriptors 0 stdin 1 stdout 2 stderr shell

Input Redirection open(input_file, O_RDONLY) file descriptors 0 stdin 1 stdout 2 stderr file descriptors 0 stdin 1 stdout 2 stderr shell shell

Input Redirection open(input_file, O_RDONLY) file descriptors 0 stdin 1 stdout 2 stderr file descriptors 0 stdin 1 stdout 2 stderr 3 input_file shell shell

Input Redirection close(0) file descriptors 0 stdin 1 stdout 2 stderr 3 input_file shell shell

Input Redirection dup(3) file descriptors 0 stdin 1 stdout 2 stderr 1 stdout 2 stderr 3 input_file shell shell

Input Redirection dup(3) file descriptors 0 stdin 1 stdout 2 stderr 0 input_file 1 stdout 2 stderr 3 input_file shell shell

Input Redirection close(3) file descriptors 0 stdin 1 stdout 2 stderr 0 input_file 1 stdout 2 stderr 3 input_file shell shell

Output Redirection shell file descriptors 0 stdin 1 stdout 2 stderr fork() file descriptors 0 stdin 1 stdout 2 stderr shell

Output Redirection open(output_file, O_RDWR | O_CREAT | O_TRUC) file descriptors 0 stdin 1 stdout 2 stderr file descriptors 0 stdin 1 stdout 2 stderr shell shell

Output Redirection open(output_file, O_RDWR | O_CREAT | O_TRUC) file descriptors 0 stdin 1 stdout 2 stderr file descriptors 0 stdin 1 stdout 2 stderr 3 output_file shell shell

Output Redirection file descriptors 0 stdin 1 stdout 2 stderr 3 output_file shell close(1) shell

Output Redirection dup(3) file descriptors 0 stdin 1 stdout 2 stderr 3 output_file shell shell

Output Redirection dup(3) file descriptors 0 stdin 1 stdout 2 stderr 1 output_file 2 stderr 3 output_file shell shell

Output Redirection close(3) file descriptors 0 stdin 1 stdout 2 stderr 1 output_file 2 stderr 3 output_file shell shell

Pipe int p1_to_p2[2]; pipe(p1_to_p2); file descriptors 0 stdin 1 stdout 2 stderr shell

Pipe int p1_to_p2[2]; pipe(p1_to_p2); file descriptors 0 stdin 1 stdout 2 stderr 3 p1_to_p2[0] 4 p1_to_p2[1] shell

Pipe shell file descriptors 0 stdin 1 stdout 2 stderr 3 p1_to_p2[0] int p1_to_p2[2]; pipe(p1_to_p2); fork() int p1_to_p2[2]; pipe(p1_to_p2); file descriptors 0 stdin 1 stdout 2 stderr 3 p1_to_p2[0] 4 p1_to_p2[1] shell

Pipe shell file descriptors 0 stdin 1 stdout 2 stderr 3 p1_to_p2[0] int p1_to_p2[2]; pipe(p1_to_p2); fork() int p1_to_p2[2]; pipe(p1_to_p2); int p1_to_p2[2]; pipe(p1_to_p2); file descriptors 0 stdin 1 stdout 2 stderr 3 p1_to_p2[0] 4 p1_to_p2[1] file descriptors 0 stdin 1 stdout 2 stderr 3 p1_to_p2[0] 4 p1_to_p2[1] shell shell

Pipe int p1_to_p2[2]; pipe(p1_to_p2); int p1_to_p2[2]; pipe(p1_to_p2); file descriptors 0 stdin 1 stdout 2 stderr 3 p1_to_p2[0] 4 p1_to_p2[1] file descriptors 0 stdin 1 stdout 2 stderr 3 p1_to_p2[0] 4 p1_to_p2[1] file descriptors 0 stdin 1 stdout 2 stderr 3 p1_to_p2[0] 4 p1_to_p2[1] shell shell shell

Pipe int p1_to_p2[2]; pipe(p1_to_p2); int p1_to_p2[2]; pipe(p1_to_p2); file descriptors 0 stdin 1 stdout 2 stderr 3 p1_to_p2[0] 4 p1_to_p2[1] file descriptors 0 stdin 1 2 stderr 3 p1_to_p2[0] 4 p1_to_p2[1] file descriptors 0 stdin 1 stdout 2 stderr 3 p1_to_p2[0] 4 p1_to_p2[1] dup(4) shell shell shell

Pipe int p1_to_p2[2]; pipe(p1_to_p2); int p1_to_p2[2]; pipe(p1_to_p2); file descriptors 0 stdin 1 stdout 2 stderr 3 p1_to_p2[0] 4 p1_to_p2[1] file descriptors 0 stdin 1 p1_to_p2[1] 2 stderr 3 p1_to_p2[0] 4 p1_to_p2[1] file descriptors 0 stdin 1 stdout 2 stderr 3 p1_to_p2[0] 4 p1_to_p2[1] dup(4) shell shell shell

Pipe int p1_to_p2[2]; pipe(p1_to_p2); int p1_to_p2[2]; pipe(p1_to_p2); file descriptors 0 stdin 1 stdout 2 stderr 3 p1_to_p2[0] 4 p1_to_p2[1] file descriptors 0 stdin 1 p1_to_p2[1] 2 stderr 3 p1_to_p2[0] 4 p1_to_p2[1] file descriptors 0 stdin 1 stdout 2 stderr 3 p1_to_p2[0] 4 p1_to_p2[1] shell shell shell

Pipe int p1_to_p2[2]; pipe(p1_to_p2); int p1_to_p2[2]; pipe(p1_to_p2); file descriptors 0 stdin 1 stdout 2 stderr 3 p1_to_p2[0] 4 p1_to_p2[1] file descriptors 0 stdin 1 p1_to_p2[1] 2 stderr file descriptors 0 stdin 1 stdout 2 stderr 3 p1_to_p2[0] 4 p1_to_p2[1] shell shell shell

Pipe int p1_to_p2[2]; pipe(p1_to_p2); int p1_to_p2[2]; pipe(p1_to_p2); file descriptors 0 stdin 1 stdout 2 stderr 3 p1_to_p2[0] 4 p1_to_p2[1] file descriptors 0 stdin 1 p1_to_p2[1] 2 stderr execvp(bin_path, argv) file descriptors 0 stdin 1 stdout 2 stderr 3 p1_to_p2[0] 4 p1_to_p2[1] shell shell shell

Pipe int p1_to_p2[2]; pipe(p1_to_p2); int p1_to_p2[2]; pipe(p1_to_p2); file descriptors 0 stdin 1 stdout 2 stderr 3 p1_to_p2[0] 4 p1_to_p2[1] file descriptors 0 stdin 1 p1_to_p2[1] 2 stderr execvp(bin_path, argv) file descriptors 0 stdin 1 stdout 2 stderr 3 p1_to_p2[0] 4 p1_to_p2[1] shell shell shell

Pipe int p1_to_p2[2]; pipe(p1_to_p2); int p1_to_p2[2]; pipe(p1_to_p2); file descriptors 0 stdin 1 stdout 2 stderr 3 p1_to_p2[0] 4 p1_to_p2[1] file descriptors 0 stdin 1 p1_to_p2[1] 2 stderr execvp(bin_path, argv) file descriptors 1 stdout 2 stderr 3 p1_to_p2[0] 4 p1_to_p2[1] dup(3) shell shell shell

Pipe int p1_to_p2[2]; pipe(p1_to_p2); int p1_to_p2[2]; pipe(p1_to_p2); file descriptors 0 stdin 1 stdout 2 stderr 3 p1_to_p2[0] 4 p1_to_p2[1] file descriptors 0 stdin 1 p1_to_p2[1] 2 stderr execvp(bin_path, argv) file descriptors 0 p1_to_p2[0] 1 stdout 2 stderr 3 p1_to_p2[0] 4 p1_to_p2[1] dup(3) shell shell shell

Pipe int p1_to_p2[2]; pipe(p1_to_p2); int p1_to_p2[2]; pipe(p1_to_p2); file descriptors 0 stdin 1 stdout 2 stderr 3 p1_to_p2[0] 4 p1_to_p2[1] file descriptors 0 stdin 1 p1_to_p2[1] 2 stderr execvp(bin_path, argv) file descriptors 0 p1_to_p2[0] 1 stdout 2 stderr 3 p1_to_p2[0] 4 p1_to_p2[1] shell shell shell

Pipe int p1_to_p2[2]; pipe(p1_to_p2); int p1_to_p2[2]; pipe(p1_to_p2); file descriptors 0 stdin 1 stdout 2 stderr 3 p1_to_p2[0] 4 p1_to_p2[1] file descriptors 0 stdin 1 p1_to_p2[1] 2 stderr execvp(bin_path, argv) file descriptors 0 p1_to_p2[0] 1 stdout 2 stderr shell shell shell

Pipe int p1_to_p2[2]; pipe(p1_to_p2); int p1_to_p2[2]; pipe(p1_to_p2); file descriptors 0 stdin 1 stdout 2 stderr 3 p1_to_p2[0] 4 p1_to_p2[1] file descriptors 0 stdin 1 p1_to_p2[1] 2 stderr execvp(bin_path, argv) file descriptors 0 p1_to_p2[0] 1 stdout 2 stderr execvp(bin_path, argv) shell shell shell

Pipe int p1_to_p2[2]; pipe(p1_to_p2); int p1_to_p2[2]; pipe(p1_to_p2); file descriptors 0 stdin 1 stdout 2 stderr 3 p1_to_p2[0] 4 p1_to_p2[1] file descriptors 0 stdin 1 p1_to_p2[1] 2 stderr execvp(bin_path, argv) file descriptors 0 p1_to_p2[0] 1 stdout 2 stderr execvp(bin_path, argv) shell shell shell

Pipe int p1_to_p2[2]; pipe(p1_to_p2); int p1_to_p2[2]; pipe(p1_to_p2); file descriptors 0 stdin 1 stdout 2 stderr file descriptors 0 stdin 1 p1_to_p2[1] 2 stderr execvp(bin_path, argv) file descriptors 0 p1_to_p2[0] 1 stdout 2 stderr execvp(bin_path, argv) shell shell shell

Pipe int p1_to_p2[2]; pipe(p1_to_p2); int p1_to_p2[2]; pipe(p1_to_p2); file descriptors 0 stdin 1 stdout 2 stderr waitpid(…) file descriptors 0 stdin 1 p1_to_p2[1] 2 stderr execvp(bin_path, argv) file descriptors 0 p1_to_p2[0] 1 stdout 2 stderr execvp(bin_path, argv) shell shell shell