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
| #include <sys/types.h>
#include <unistd.h>
#include <stdio.h>
void error(char *s);
char *data ="Some input data\
";
main()
{
int in[2], out[2], n, pid;
char buf[255];
/* In a pipe, xx[0] is for reading, xx[1] is for writing */
if (pipe(in) < 0) error("pipe in");
if (pipe(out) < 0) error("pipe out");
if ((pid=fork()) == 0) {
/* This is the child process */
/* Close stdin, stdout, stderr */
close(0);
close(1);
close(2);
/* make our pipes, our new stdin,stdout and stderr */
dup2(in[0],0);
dup2(out[1],1);
dup2(out[1],2);
/* Close the other ends of the pipes that the parent will use, because if
* we leave these open in the child, the child/parent will not get an EOF
* when the parent/child closes their end of the pipe.
*/
close(in[1]);
close(out[0]);
/* Over-write the child process with the hexdump binary */
execl("/usr/bin/hexdump","hexdump","-C", (char *)NULL);
error("Could not exec hexdump");
}
printf("Spawned 'hexdump -C' as a child process at pid %d\
", pid);
/* This is the parent process */
/* Close the pipe ends that the child uses to read from / write to so
* the when we close the others, an EOF will be transmitted properly.
*/
close(in[0]);
close(out[1]);
printf("<- %s", data);
/* Write some data to the childs input */
write(in[1], data, strlen(data));
/* Because of the small amount of data, the child may block unless we
* close it's input stream. This sends an EOF to the child on it's
* stdin.
*/
close(in[1]);
/* Read back any output */
n = read(out[0], buf, 250);
buf[n] = 0;
printf("-> %s",buf);
exit(0);
}
void error(char *s)
{
perror(s);
exit(1);
} |
