Question

Using the file descriptor table for a process, answer the following questions. Note: the dup(), pipe() , and open() system calls always use the lowest numbered available file descriptor posi-tion.

(a) Label which entries in Table 2 refer to stdin, stdout, andstderr

0	1	2	3	4	5

(b) Assume that stdin, stdout, and stderr are all open. Label in Table 3 what the file descriptor table would look like after the following code is executed:

int fd[2];
close(1);
pipe(fd);

0	1	2	3	4	5

(c) Assuming a fresh file descriptor table with only stdin, stdout, and stderr open, show in Table 4 the contents of file descriptor table after thefollowing code is executed:

close(2);
dup(1);

0	1	2	3	4	5

Answer 1

Standard file descriptors(fd) and the corresponding standard streams

fd	stream
0	stdin
1	stdout
2	stderr

Using the file descriptor table for a process, answer the following questions. Note: the dup(), pipe() , and open() system calls always use the lowest numbered available file descriptor posi-tion.

(a) Label which entries in Table 2 refer to stdin, stdout, and stderr

0	1		2	3	4	5
stdin		stdout	stderr

(b) Assume that stdin, stdout, and stderr are all open. Label in Table 3 what the file descriptor table would look like after the following code is executed:

int fd[2];
close(1); // closing the stdin

pipe(fd); // opening new file descriptor fd[0], fd[1]

0	1	2	3	4	5
stdin	fd[0]	stderr	fd[1]

(c) Assuming a fresh file descriptor table with only stdin, stdout, and stderr open, show in Table 4 the contents of file descriptor table after thefollowing code is executed:

close(2); //closing the stderr
dup(1); // new file descriptor newfd is a duplicate of file descriptor 1 (stdout)

0	1	2	3	4	5
stdin	stdout	newfd(stdout)