stdlib/FreeBSD/grantpt.3

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  32 .\" $FreeBSD: src/lib/libc/stdlib/grantpt.3,v 1.3 2003/09/14 13:41:57 ru Exp $
  33 .\"
  34 .Dd December 23, 2002
  35 .Os
  36 .Dt GRANTPT 3
  37 .Sh NAME
  38 .Nm grantpt ,
  39 .Nm ptsname ,
  40 .Nm unlockpt ,
  41 .Nm posix_openpt
  42 .Nd pseudo-terminal access functions
  43 .Sh LIBRARY
  44 .Lb libc
  45 .Sh SYNOPSIS
  46 .In stdlib.h
  47 .Ft int
  48 .Fn grantpt "int fildes"
  49 .Ft "char *"
  50 .Fn ptsname "int fildes"
  51 .Ft int
  52 .Fn unlockpt "int fildes"
  53 .In fcntl.h
  54 .Ft int
  55 .Fn posix_openpt "int mode"
  56 .Sh DESCRIPTION
  57 The
  58 .Fn grantpt ,
  59 .Fn ptsname ,
  60 .Fn unlockpt ,
  61 and
  62 .Fn posix_openpt
  63 functions allow access to pseudo-terminal devices.
  64 The first three functions accept a file descriptor
  65 that references the master half of a pseudo-terminal pair.
  66 This file descriptor is created with
  67 .Fn posix_openpt .
  68 .Pp
  69 The
  70 .Fn grantpt
  71 function is used to establish ownership and permissions
  72 of the slave device counterpart to the master device
  73 specified with
  74 .Fa fildes .
  75 The slave device's ownership is set to the real user ID
  76 of the calling process, and the permissions are set to
  77 user readable-writable and group writable.
  78 The group owner of the slave device is also set to the
  79 group
  80 .Dq Li tty
  81 if it exists on the system; otherwise, it
  82 is left untouched.
  83 .Pp
  84 The
  85 .Fn ptsname
  86 function returns the full pathname of the slave device
  87 counterpart to the master device specified with
  88 .Fa fildes .
  89 This value can be used
  90 to subsequently open the appropriate slave after
  91 .Fn posix_openpt
  92 and
  93 .Fn grantpt
  94 have been called.
  95 .Pp
  96 The
  97 .Fn unlockpt
  98 function clears the lock held on the pseudo-terminal pair
  99 for the master device specified with
 100 .Fa fildes .
 101 .Pp
 102 The
 103 .Fn posix_openpt
 104 function opens the first available master pseudo-terminal
 105 device and returns a descriptor to it.
 106 The
 107 .Fa mode
 108 argument
 109 specifies the flags used for opening the device:
 110 .Bl -tag -width ".Dv O_NOCTTY"
 111 .It Dv O_RDWR
 112 Open for reading and writing.
 113 .It Dv O_NOCTTY
 114 If set, do not allow the terminal to become
 115 the controlling terminal for the calling process.
 116 .El
 117 .Sh RETURN VALUES
 118 .Rv -std grantpt unlockpt
 119 .Pp
 120 The
 121 .Fn ptsname
 122 function returns a pointer to the name
 123 of the slave device on success; otherwise a
 124 .Dv NULL
 125 pointer is returned and the global variable
 126 .Va errno
 127 is set to indicate the error.
 128 .Pp
 129 The
 130 .Fn posix_openpt
 131 function returns a file descriptor to the first
 132 available master pseudo-terminal device on success;
 133 otherwise \-1 is returned and the global variable
 134 .Va errno
 135 is set to indicate the error.
 136 .Sh ERRORS
 137 The
 138 .Fn grantpt ,
 139 .Fn ptsname ,
 140 and
 141 .Fn unlockpt
 142 functions may fail and set
 143 .Va errno
 144 to:
 145 .Bl -tag -width Er
 146 .It Bq Er EINVAL
 147 .Fa fildes
 148 is not a master pseudo-terminal device.
 149 .El
 150 .Pp
 151 In addition, the
 152 .Fn grantpt
 153 function may set
 154 .Va errno
 155 to:
 156 .Bl -tag -width Er
 157 .It Bq Er EACCES
 158 The slave pseudo-terminal device could not be accessed.
 159 .El
 160 .Pp
 161 The
 162 .Fn posix_openpt
 163 function may fail and set
 164 .Va errno
 165 to:
 166 .Bl -tag -width Er
 167 .It Bq Er EINVAL
 168 .Fa mode
 169 consists of an invalid mode bit.
 170 .It Bq Er EAGAIN
 171 The system has no available pseudo-terminal devices.
 172 .El
 173 .Pp
 174 The
 175 .Fn grantpt ,
 176 .Fn ptsname ,
 177 and
 178 .Fn unlockpt
 179 functions may also fail and set
 180 .Va errno
 181 for any of the errors specified for the
 182 .Xr fstat 2
 183 system call.
 184 .Pp
 185 The
 186 .Fn posix_openpt
 187 function may also fail and set
 188 .Va errno
 189 for any of the errors specified for the
 190 .Xr open 2
 191 system call.
 192 .Sh SEE ALSO
 193 .Xr open 2 ,
 194 .Xr pty 4 ,
 195 .Xr tty 4
 196 .Sh STANDARDS
 197 The
 198 .Fn grantpt ,
 199 .Fn ptsname ,
 200 .Fn unlockpt ,
 201 and
 202 .Fn posix_openpt
 203 functions conform to
 204 .St -p1003.1-2001 .
 205 .Sh HISTORY
 206 The
 207 .Fn grantpt ,
 208 .Fn ptsname ,
 209 .Fn unlockpt ,
 210 and
 211 .Fn posix_openpt
 212 functions appeared in
 213 .Fx 5.0 .
 214 .Sh NOTES
 215 The purpose of the
 216 .Fn unlockpt
 217 function has no meaning in
 218 .Fx .
 219 .Pp
 220 The flag
 221 .Dv O_NOCTTY
 222 is included for compatibility; in
 223 .Fx ,
 224 opening a terminal does not cause it to become
 225 a process's controlling terminal.