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openpty, forkpty - auxiliary functions to obtain a pseudo-terminal



      openpty, forkpty - auxiliary functions to obtain a pseudo-terminal


      System Utilities Library (libutil, -lutil)


      #include <sys/types.h>
      #include <sys/ioctl.h>
      #include <termios.h>
      #include <libutil.h>
      openpty(int *amaster, int *aslave, char *name, struct termios *termp,
              struct winsize *winp);
      forkpty(int *amaster, char *name, struct termios *termp,
              struct winsize *winp);


      The function openpty() attempts to obtain the next available pseudo-ter‐
      minal from the system (see pty(4)).  If it successfully finds one, it
      subsequently tries to change the ownership of the slave device to the
      real UID of the current process, the group membership to the group “tty”
      (if such a group exists in the system), the access permissions for read‐
      ing and writing by the owner, and for writing by the group, and to inval‐
      idate any current use of the line by calling revoke(2).
      If the argument name is not NULL, openpty() copies the pathname of the
      slave pty to this area.  The caller is responsible for allocating the
      required space in this array.
      If the arguments termp or winp are not NULL, openpty() initializes the
      termios and window size settings from the structures these arguments
      point to, respectively.
      Upon return, the open file descriptors for the master and slave side of
      the pty are returned in the locations pointed to by amaster and aslave,
      The forkpty() function first calls openpty() to obtain the next available
      pseudo-terminal from the system.  Upon success, it forks off a new pro‐
      cess.  In the child process, it closes the descriptor for the master side
      of the pty, and calls login_tty(3) for the slave pty.  In the parent pro‐
      cess, it closes the descriptor for the slave side of the pty.  The argu‐
      ments amaster, name, termp, and winp have the same meaning as described
      for openpty().
      The openpty() function returns 0 on success, or -1 on failure.
      The forkpty() function returns -1 on failure, 0 in the slave process, and
      the process ID of the slave process in the parent process.


      On failure, openpty() will set the global variable errno to ENOENT.
      In addition to this, forkpty() may set it to any value as described for
      chmod(2), chown(2), fork(2), getuid(2), open(2), revoke(2), login_tty(3),
      pty(4), termios(4), group(5)


      The calling process must have an effective UID of super-user in order to
      perform all the intended actions.  No notification will occur if
      openpty() or forkpty() failed to proceed with one of the described steps,
      as long as they could at least allocate the pty at all (and create the
      new process in the case of forkpty()).


Based on BSD UNIX
FreeBSD is an advanced operating system for x86 compatible (including Pentium and Athlon), amd64 compatible (including Opteron, Athlon64, and EM64T), UltraSPARC, IA-64, PC-98 and ARM architectures. It is derived from BSD, the version of UNIX developed at the University of California, Berkeley. It is developed and maintained by a large team of individuals. Additional platforms are in various stages of development.