xref: /netbsd/lib/libc/gen/ttyname.3 (revision c4a72b64)
1.\"	$NetBSD: ttyname.3,v 1.12 2002/10/01 16:48:35 wiz Exp $
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34.\"     @(#)ttyname.3	8.1 (Berkeley) 6/4/93
35.\"
36.Dd June 4, 1993
37.Dt TTYNAME 3
38.Os
39.Sh NAME
40.Nm ttyname ,
41.Nm isatty ,
42.Nm ttyslot
43.Nd get name of associated terminal (tty) from file descriptor
44.Sh LIBRARY
45.Lb libc
46.Sh SYNOPSIS
47.Fd #include \*[Lt]unistd.h\*[Gt]
48.Ft char *
49.Fn ttyname "int fd"
50.Ft int
51.Fn isatty "int fd"
52.Fd #include \*[Lt]stdlib.h\*[Gt]
53.Ft int
54.Fn ttyslot
55.Sh DESCRIPTION
56These functions operate on the system file descriptors for terminal
57type devices.
58These descriptors are not related to the standard
59.Tn I/O
60.Dv FILE
61typedef, but refer to the special device files found in
62.Pa /dev
63and named
64.Pa /dev/tty Ns Em xx
65and for which an entry exists
66in the initialization file
67.Pa /etc/ttys .
68(See
69.Xr ttys 5 . )
70.Pp
71The
72.Fn isatty
73function
74determines if the file descriptor
75.Fa fd
76refers to a valid
77terminal type device.
78.Pp
79The
80.Fn ttyname
81function
82gets the related device name of
83a file descriptor for which
84.Fn isatty
85is true.
86.Pp
87The
88.Fn ttyslot
89function
90fetches the current process' control terminal number from the
91.Xr ttys 5
92file entry.
93.Sh RETURN VALUES
94The
95.Fn ttyname
96function
97returns the null terminated name if the device is found and
98.Fn isatty
99is true; otherwise
100a
101.Dv NULL
102pointer is returned and
103.Va errno
104is set to indicate the error.
105.Pp
106The
107.Fn isatty
108function returns 1 if
109.Fa fd
110is associated with a terminal device; otherwise it returns 0 and
111.Va errno
112is set to indicate the error.
113.Pp
114The
115.Fn ttyslot
116function
117returns the unit number of the device file if found; otherwise
118the value zero is returned.
119.Sh FILES
120.Bl -tag -width /etc/ttys -compact
121.It Pa /dev/\(**
122.It Pa /etc/ttys
123.El
124.Sh ERRORS
125The
126.Fn ttyname
127and
128.Fn isatty
129functions will fail if:
130.Bl -tag -width Er
131.It Bq Er EBADF
132The
133.Fa fd
134argument is not a valid file descriptor.
135.It Bq Er ENOTTY
136The
137.Fa fd
138argument does not refer to a terminal device.
139.El
140.Sh SEE ALSO
141.Xr ioctl 2 ,
142.Xr ttys 5
143.Sh STANDARDS
144The
145.Fn ttyname
146and
147.Fn isatty
148functions conform to
149.St -p1003.1-90 .
150.Sh HISTORY
151A
152.Fn isatty ,
153.Fn ttyname ,
154and
155.Fn ttyslot
156function
157appeared in
158.At v7 .
159.Sh BUGS
160The
161.Fn ttyname
162function leaves its result in an internal static object and returns
163a pointer to that object.
164Subsequent calls to
165.Fn ttyname
166will modify the same object.
167