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