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TTYNAME(3)		    Library Functions Manual		    TTYNAME(3)

NAME
       ttyname,	 ttyname_r,  isatty  --	 get name of associated	terminal (tty)
       from file descriptor

LIBRARY
       Standard	C Library (libc, -lc)

SYNOPSIS
       #include	<unistd.h>

       char *
       ttyname(int fd);

       int
       ttyname_r(int fd, char *buf, size_t len);

       int
       isatty(int fd);

DESCRIPTION
       These functions operate on file descriptors for terminal	type devices.

       The isatty() function determines	if the file descriptor fd refers to  a
       valid terminal type device.

       The  ttyname() function gets the	related	device name of a file descrip-
       tor for which isatty() is true.

       The ttyname() function returns the name stored in a static buffer which
       will be overwritten on  subsequent  calls.   The	 ttyname_r()  function
       takes a buffer and length as arguments to avoid this problem.

RETURN VALUES
       The isatty() function returns 1 if fd refers to a terminal type device;
       otherwise,  it  returns 0 and may set errno to indicate the error.  The
       ttyname() function returns the null terminated name if  the  device  is
       found  and isatty() is true; otherwise a	NULL pointer is	returned.  The
       ttyname_r() function returns 0 if successful.  Otherwise	an error  num-
       ber is returned.

ERRORS
       These functions may fail	if:

       [EBADF]		  The fd argument is not a valid file descriptor.

       [ENOTTY]		  The file associated with fd is not a terminal.

       Additionally, ttyname_r() may fail if:

       [ERANGE]		  The  bufsize	argument is smaller than the length of
			  the string to	be returned.

SEE ALSO
       fdevname(3), ptsname(3),	tcgetattr(3), tty(4)

HISTORY
       The isatty() and	ttyname() functions appeared in	Version	7  AT&T	 UNIX.
       The ttyname_r() function	appeared in FreeBSD 6.0.

FreeBSD	14.3			 July 18, 2014			    TTYNAME(3)

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<https://man.freebsd.org/cgi/man.cgi?query=isatty&sektion=3&manpath=FreeBSD+14.3-RELEASE+and+Ports>

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