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
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
|
/*************************************************************************\
* Copyright (C) Michael Kerrisk, 2018. *
* *
* This program is free software. You may use, modify, and redistribute it *
* under the terms of the GNU Lesser General Public License as published *
* by the Free Software Foundation, either version 3 or (at your option) *
* any later version. This program is distributed without any warranty. *
* See the files COPYING.lgpl-v3 and COPYING.gpl-v3 for details. *
\*************************************************************************/
/* Listing 64-2 */
/* pty_fork.c
Implements ptyFork(), a function that creates a child process connected to
the parent (i.e., the calling process) via a pseudoterminal (pty). The child
is placed in a new session, with the pty slave as its controlling terminal,
and its standard input, output, and error connected to the pty slave.
In the parent, 'masterFd' is used to return the file descriptor for the
pty master.
If 'slaveName' is non-NULL, then it is used to return the name of the pty
slave. If 'slaveName' is not NULL, then 'snLen' should be set to indicate
the size of the buffer pointed to by 'slaveName'.
If 'slaveTermios' and 'slaveWS' are non-NULL, then they are used respectively
to set the terminal attributes and window size of the pty slave.
Returns:
in child: 0
in parent: PID of child or -1 on error
*/
#include <fcntl.h>
#include <termios.h>
#include <sys/ioctl.h>
#include "pty_master_open.h"
#include "pty_fork.h" /* Declares ptyFork() */
#include "af_unix_hdr.h"
#define MAX_SNAME 1000 /* Maximum size for pty slave name */
pid_t
ptyFork(int *masterFd, char *slaveName, size_t snLen,
const struct termios *slaveTermios, const struct winsize *slaveWS)
{
int mfd, slaveFd, savedErrno;
pid_t childPid;
char slname[MAX_SNAME];
mfd = ptyMasterOpen(slname, MAX_SNAME);
if (mfd == -1)
return -1;
if (slaveName != NULL) { /* Return slave name to caller */
if (strlen(slname) < snLen) {
strncpy(slaveName, slname, snLen);
} else { /* 'slaveName' was too small */
close(mfd);
errno = EOVERFLOW;
return -1;
}
}
childPid = fork();
if (childPid == -1) { /* fork() failed */
savedErrno = errno; /* close() might change 'errno' */
close(mfd); /* Don't leak file descriptors */
errno = savedErrno;
return -1;
}
if (childPid != 0) { /* Parent */
*masterFd = mfd; /* Only parent gets master fd */
return childPid; /* Like parent of fork() */
}
/* Child falls through to here */
if (setsid() == -1) /* Start a new session */
err_exit("ptyFork:setsid");
close(mfd); /* Not needed in child */
slaveFd = open(slname, O_RDWR); /* Becomes controlling tty */
if (slaveFd == -1)
err_exit("ptyFork:open-slave");
/* #ifdef TIOCSCTTY /\* Acquire controlling tty on BSD *\/ */
/* if (ioctl(slaveFd, TIOCSCTTY, 0) == -1) */
/* err_exit("ptyFork:ioctl-TIOCSCTTY"); */
/* #endif */
if (slaveTermios != NULL) /* Set slave tty attributes */
if (tcsetattr(slaveFd, TCSANOW, slaveTermios) == -1)
err_exit("ptyFork:tcsetattr");
if (slaveWS != NULL) /* Set slave tty window size */
if (ioctl(slaveFd, TIOCSWINSZ, slaveWS) == -1)
err_exit("ptyFork:ioctl-TIOCSWINSZ");
/* Duplicate pty slave to be child's stdin, stdout, and stderr */
if (dup2(slaveFd, STDIN_FILENO) != STDIN_FILENO)
err_exit("ptyFork:dup2-STDIN_FILENO");
if (dup2(slaveFd, STDOUT_FILENO) != STDOUT_FILENO)
err_exit("ptyFork:dup2-STDOUT_FILENO");
if (dup2(slaveFd, STDERR_FILENO) != STDERR_FILENO)
err_exit("ptyFork:dup2-STDERR_FILENO");
if (slaveFd > STDERR_FILENO) /* Safety check */
close(slaveFd); /* No longer need this fd */
return 0; /* Like child of fork() */
}
|
