man3/openpty.3

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  32 .TH OPENPTY 3  "2003-07-18" "BSD" "Linux Programmer's Manual"
  33 .SH NAME
  34 openpty, login_tty, forkpty \- tty utility functions
  35 .SH SYNOPSIS
  36 .B #include <pty.h>
  37 \ /* for openpty and forkpty */
  38 .br
  39 .B #include <utmp.h>
  40 /* for login_tty */
  41 .sp
  42 .BI "int openpty(int *" amaster ", int *" aslave ", char *" name ", struct termios *" termp ", struct winsize * " winp );
  43 .sp
  44 .BI "int login_tty(int " fd );
  45 .sp
  46 .BI "pid_t forkpty(int *" amaster ", char *" name ", struct termios *" termp ", struct winsize *" winp );
  47 .sp
  48 Link with -lutil.
  49 .SH DESCRIPTION
  50 The
  51 .B openpty()
  52 function finds an available pseudo-tty and returns file descriptors
  53 for the master and slave in
  54 .I amaster
  55 and
  56 .IR aslave .
  57 If
  58 .I name
  59 is not NULL, the filename of the slave is returned in
  60 .IR name .
  61 If
  62 .I termp
  63 is not NULL, the terminal parameters of the slave will be set to the
  64 values in
  65 .IR termp .
  66 If
  67 .I winp
  68 is not NULL, the window size of the slave will be set to the values in
  69 .IR winp .
  70
  71 The
  72 .B login_tty()
  73 function prepares for a login on the tty
  74 .I fd
  75 (which may be a real tty device, or the slave of a pseudo-tty as
  76 returned by
  77 .BR openpty() )
  78 by creating a new session, making
  79 .I fd
  80 the controlling terminal for the current process, setting
  81 .I fd
  82 to be the standard input, output, and error streams of the current
  83 process, and closing
  84 .IR fd .
  85
  86 The
  87 .B forkpty()
  88 function combines
  89 .BR openpty() ,
  90 .BR fork() ,
  91 and
  92 .B login_tty()
  93 to create a new process operating in a pseudo-tty.  The file
  94 descriptor of the master side of the pseudo-tty is returned in
  95 .IR amaster ,
  96 and the filename of the slave in
  97 .I name
  98 if it is not NULL.  The
  99 .I termp
 100 and
 101 .I winp
 102 parameters, if not NULL,
 103 will determine the terminal attributes and window size of the slave
 104 side of the pseudo-tty.
 105 .SH "RETURN VALUES"
 106 If a call to
 107 .BR openpty() ,
 108 .BR login_tty() ,
 109 or
 110 .B forkpty()
 111 is not successful, \-1 is returned and
 112 .I errno
 113 is set to indicate the error.  Otherwise,
 114 .BR openpty() ,
 115 .BR login_tty() ,
 116 and the child process of
 117 .B forkpty()
 118 return 0, and the parent process of
 119 .B forkpty()
 120 returns the process ID of the child process.
 121 .SH ERRORS
 122 .B openpty()
 123 will fail if:
 124 .TP
 125 .B ENOENT
 126 There are no available ttys.
 127 .LP
 128 .B login_pty()
 129 will fail if
 130 .B ioctl()
 131 fails to set
 132 .I fd
 133 to the controlling terminal of the current process.
 134 .LP
 135 .B forkpty()
 136 will fail if either
 137 .B openpty()
 138 or
 139 .B fork()
 140 fails.
 141 .SH NOTE
 142 These functions are included in libutil, hence you'll need to add
 143 .B \-lutil
 144 to your compiler commandline.
 145 .SH FILES
 146 .I /dev/[pt]ty[pqrstuwxyzabcdePQRST][0123456789abcdef]
 147 .SH "CONFORMING TO"
 148 These are BSD functions, present in libc5 and glibc2.
 149 .SH BUGS
 150 Nobody knows how much space should be reserved for
 151 .IR name .
 152 So, calling
 153 .B openpty()
 154 or
 155 .B forkpty()
 156 with non-NULL
 157 .I name
 158 may not be secure.
 159 .SH "SEE ALSO"
 160 .BR fork (2)