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ttyslot(3) [minix man page]

TTYSLOT(3)						     Library Functions Manual							TTYSLOT(3)

NAME
ttyslot, fttyslot - utmp slot number SYNOPSIS
#define _MINIX_SOURCE 1 #include <unistd.h> int ttyslot(void) int fttyslot(int fd) DESCRIPTION
Ttyslot() returns the index of the login terminal in the utmp file. It tries fttyslot() on file descriptors 0, 1, and 2 to find the index. Fttyslot() returns the utmp index of the terminal associated with file descriptor fd. First it tries to map fd to a terminal name with ttyname(3), then it searches the ttytab(5) database with the getttyent(3) function for this terminal. This means that the utmp slot number is the same as the ttytab entry number counting from 1. The value 0 is returned if no slot number can be found for a file descriptor. SEE ALSO
ttyname(3), getttyent(3), utmp(5), ttytab(5), init(8). NOTES
Since 0 is used as an error return this means that the first entry in the utmp file is not used. Ttyslot() is often found in a UNIX implementation, fttyslot() is Minix specific. AUTHOR
Kees J. Bot (kjb@cs.vu.nl) TTYSLOT(3)

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

NAME
ttyslot - find the slot of the current user's terminal in some file SYNOPSIS
#include <unistd.h> /* on BSD-like systems, and Linux */ #include <stdlib.h> /* on System V-like systems */ int ttyslot(void); Feature Test Macro Requirements for glibc (see feature_test_macros(7)): ttyslot(): _BSD_SOURCE || _XOPEN_SOURCE && _XOPEN_SOURCE_ < 500 && _XOPEN_SOURCE_EXTENDED DESCRIPTION
The legacy function ttyslot() returns the index of the current user's entry in some file. Now "What file?" you ask. Well, let's first look at some history. Ancient History There used to be a file /etc/ttys in UNIX V6, that was read by the init(8) program to find out what to do with each terminal line. Each line consisted of three characters. The first character was either '0' or '1', where '0' meant "ignore". The second character denoted the terminal: '8' stood for "/dev/tty8". The third character was an argument to getty(8) indicating the sequence of line speeds to try ('-' was: start trying 110 baud). Thus a typical line was "18-". A hang on some line was solved by changing the '1' to a '0', signaling init, changing back again, and signaling init again. In UNIX V7 the format was changed: here the second character was the argument to getty(8) indicating the sequence of line speeds to try ('0' was: cycle through 300-1200-150-110 baud; '4' was for the on-line console DECwriter) while the rest of the line contained the name of the tty. Thus a typical line was "14console". Later systems have more elaborate syntax. System V-like systems have /etc/inittab instead. Ancient History (2) On the other hand, there is the file /etc/utmp listing the people currently logged in. It is maintained by login(1). It has a fixed size, and the appropriate index in the file was determined by login(1) using the ttyslot() call to find the number of the line in /etc/ttys (counting from 1). The semantics of ttyslot Thus, the function ttyslot() returns the index of the controlling terminal of the calling process in the file /etc/ttys, and that is (usu- ally) the same as the index of the entry for the current user in the file /etc/utmp. BSD still has the /etc/ttys file, but System V-like systems do not, and hence cannot refer to it. Thus, on such systems the documentation says that ttyslot() returns the current user's index in the user accounting data base. RETURN VALUE
If successful, this function returns the slot number. On error (e.g., if none of the file descriptors 0, 1 or 2 is associated with a ter- minal that occurs in this data base) it returns 0 on UNIX V6 and V7 and BSD-like systems, but -1 on System V-like systems. CONFORMING TO
SUSv1; marked as LEGACY in SUSv2; removed in POSIX.1-2001. SUSv2 requires -1 on error. NOTES
The utmp file is found various places on various systems, such as /etc/utmp, /var/adm/utmp, /var/run/utmp. The glibc2 implementation of this function reads the file _PATH_TTYS, defined in <ttyent.h> as "/etc/ttys". It returns 0 on error. Since Linux systems do not usually have "/etc/ttys", it will always return 0. Minix also has fttyslot(fd). SEE ALSO
getttyent(3), ttyname(3), utmp(5) COLOPHON
This page is part of release 3.44 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/. GNU
2010-09-20 TTYSLOT(3)
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