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  48 .Dd February 5, 2022
  49 .Dt PTSNAME 3C
  50 .Os
  51 .Sh NAME
  52 .Nm ptsname
  53 .Nd get the name of the subsidiary device of a pseudo-terminal
  54 .Sh SYNOPSIS
  55 .In stdlib.h
  56 .Ft char *
  57 .Fo ptsname
  58 .Fa "int fildes"
  59 .Fc
  60 .Sh DESCRIPTION
  61 The
  62 .Fn ptsname
  63 function returns the name of the pseudo-terminal subsidiary device associated
  64 with a pseudo-terminal manager device.
  65 The
  66 .Fa fildes
  67 argument is a file descriptor returned from a successful open of the
  68 pseudo-terminal manager device; e.g., by calling
  69 .Xr posix_openpt 3C
  70 or by performing an
  71 .Xr open 2
  72 of the
  73 .Xr ptm 7D
  74 device.
  75 .Pp
  76 The
  77 .Fn ptsname
  78 function returns a pointer to a string containing the null-terminated
  79 path name of the subsidiary device.
  80 This string is of the form
  81 .Pa /dev/pts/N ,
  82 where
  83 .Sy N
  84 is a non-negative integer.
  85 .Sh RETURN VALUES
  86 If successful, the
  87 .Fn ptsname
  88 function returns a pointer to a string which is the name of the pseudo-terminal
  89 subsidiary device.
  90 This value points to a static data area that is overwritten by each call to
  91 .Fn ptsname .
  92 .Pp
  93 Upon failure,
  94 .Fn ptsname
  95 returns
  96 .Dv NULL .
  97 This could occur if
  98 .Fa fildes
  99 is an invalid file descriptor or if the subsidiary device name does not exist
 100 in the file system.
 101 .Sh INTERFACE STABILITY
 102 .Sy Committed
 103 .Sh MT LEVEL
 104 .Sy Safe
 105 .Sh SEE ALSO
 106 .Xr open 2 ,
 107 .Xr grantpt 3C ,
 108 .Xr posix_openpt 3C ,
 109 .Xr ttyname 3C ,
 110 .Xr unlockpt 3C ,
 111 .Xr attributes 5 ,
 112 .Xr standards 5 ,
 113 .Xr ptm 7D ,
 114 .Xr pts 7D