1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
|
/*
* mailer - open a pipe to the mail command and send the user
* mail.
*/
#include <stdio.h>
main()
{
FILE *fp;
int pid, pipefds[2];
char *username, *getlogin();
/*
* Get the user's name.
*/
if ((username = getlogin()) == NULL) {
fprintf(stderr, "Who are you?\n");
exit(1);
}
/*
* Create the pipe. This has to be done
* BEFORE the fork.
*/
if (pipe(pipefds) < 0) {
perror("pipe");
exit(1);
}
if ((pid = fork()) < 0) {
perror("fork");
exit(1);
}
/*
* The child process executes the stuff inside
* the if.
*/
if (pid == 0) {
/*
* Make the read side of the pipe our
* standard input.
*/
close(0);
dup(pipefds[0]);
close(pipefds[0]);
/*
* Close the write side of the pipe;
* we'll let our output go to the screen.
*/
close(pipefds[1]);
/*
* Execute the command "mail username".
*/
execl("/bin/mail", "mail", username, 0);
perror("exec");
exit(1);
}
/*
* The parent executes this code.
*/
/*
* Close the read side of the pipe; we
* don't need it (and the child is not
* writing on the pipe anyway).
*/
close(pipefds[0]);
/*
* Convert the write side of the pipe to stdio.
*/
fp = fdopen(pipefds[1], "w");
/*
* Send a message, close the pipe.
*/
fprintf(fp, "Hello from your program.\n");
fclose(fp);
/*
* Wait for the process to terminate.
*/
while (wait((int *) 0) != pid)
;
exit(0);
}
|
