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ttyslot(3) [netbsd man page]

TTYNAME(3)						   BSD Library Functions Manual 						TTYNAME(3)

ttyname, ttyname_r, isatty, ttyslot -- 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); #include <stdlib.h> int ttyslot(void); DESCRIPTION
These functions operate on the system file descriptors for terminal type devices. These descriptors are not related to the standard I/O FILE typedef, but refer to the special device files found in /dev and named /dev/ttyxx and for which an entry exists in the initialization file /etc/ttys (see ttys(5)), or for pseudo-terminal devices created in ptyfs and named /dev/pts/n. 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 descriptor for which isatty() is true. The ttyname_r() is the reentrant ver- sion of the above, and it places the results in buf. If there is not enough space to place the results (indicated by len), then it returns an error. The ttyslot() function fetches the current process' control terminal number from the ttys(5) file entry. If the terminal is a pseudo-termi- nal, and there is no special entry in the ttys(5) file for it, the slot number returned is 1 + (last slot number) + minor(tty). This will return a consistent and unique number for each pseudo-terminal device without requiring one to enumerate all of them in ttys(5). IMPLEMENTATION NOTES
As an optimisation, these functions attempt to obtain information about all devices from the /var/run/dev.cdb database, if it exists. If the database exists but is out of date, then these functions may produce incorrect results. The database should be updated using the dev_mkdb(8) command. RETURN VALUES
The ttyname() function returns the NUL-terminated name if the device is found and isatty() is true; otherwise a NULL pointer is returned and errno is set to indicate the error. The ttyname_r() functions returns 0 on success and an error code on failure. The isatty() function returns 1 if fd is associated with a terminal device; otherwise it returns 0 and errno is set to indicate the error. The ttyslot() function returns the unit number of the device file if found; otherwise the value zero is returned. FILES
/dev/* /etc/ttys ERRORS
The ttyname(), ttyname_r(), and isatty() functions will fail if: [EBADF] The fd argument is not a valid file descriptor. [ENOTTY] The fd argument does not refer to a terminal device. The ttyname_r() function will also fail if: [ENOENT] The terminal device is not found. This can happen if the device node has been removed after it was opened. [ERANGE] The buffer provided is not large enough to fit the result. SEE ALSO
ioctl(2), ttys(5), dev_mkdb(8) STANDARDS
The ttyname() and isatty() functions conform to ISO/IEC 9945-1:1990 (``POSIX.1''). HISTORY
isatty(), ttyname(), and ttyslot() functions appeared in Version 7 AT&T UNIX. BUGS
The ttyname() function leaves its result in an internal static object and returns a pointer to that object. Subsequent calls to ttyname() will modify the same object. BSD
June 1, 2012 BSD

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TTYNAME(3)                                                   Linux Programmer's Manual                                                  TTYNAME(3)

ttyname, ttyname_r - return name of a terminal SYNOPSIS
#include <unistd.h> char *ttyname(int fd); int ttyname_r(int fd, char *buf, size_t buflen); DESCRIPTION
The function ttyname() returns a pointer to the null-terminated pathname of the terminal device that is open on the file descriptor fd, or NULL on error (for example, if fd is not connected to a terminal). The return value may point to static data, possibly overwritten by the next call. The function ttyname_r() stores this pathname in the buffer buf of length buflen. RETURN VALUE
The function ttyname() returns a pointer to a pathname on success. On error, NULL is returned, and errno is set appropriately. The func- tion ttyname_r() returns 0 on success, and an error number upon error. ERRORS
EBADF Bad file descriptor. ENOTTY File descriptor does not refer to a terminal device. ERANGE (ttyname_r()) buflen was too small to allow storing the pathname. ENODEV File descriptor refers to a slave pseudoterminal device but the corresponding pathname could not be found (see NOTES). ATTRIBUTES
For an explanation of the terms used in this section, see attributes(7). +------------+---------------+------------------------+ |Interface | Attribute | Value | +------------+---------------+------------------------+ |ttyname() | Thread safety | MT-Unsafe race:ttyname | +------------+---------------+------------------------+ |ttyname_r() | Thread safety | MT-Safe | +------------+---------------+------------------------+ CONFORMING TO
POSIX.1-2001, POSIX.1-2008, 4.2BSD. NOTES
A process that keeps a file descriptor that refers to a pts(4) device open when switching to another mount namespace that uses a different /dev/ptmx instance may still accidentally find that a device path of the same name for that file descriptor exists. However, this device path refers to a different device and thus can't be used to access the device that the file descriptor refers to. Calling ttyname() or ttyname_r() on the file descriptor in the new mount namespace will cause these functions to return NULL and set errno to ENODEV. SEE ALSO
tty(1), fstat(2), ctermid(3), isatty(3), pts(4) COLOPHON
This page is part of release 4.15 of the Linux man-pages project. A description of the project, information about reporting bugs, and the latest version of this page, can be found at Linux 2017-05-03 TTYNAME(3)
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