TTYSRCH(5) File Formats and Configurations TTYSRCH(5)

NAME

ttysrch - directory search list for ttyname

DESCRIPTION

ttysrch is an optional file that is used by the ttyname library
routine. This file contains the names of directories in /dev that
contain terminal and terminal-related device files. The purpose of
this file is to improve the performance of ttyname by indicating
which subdirectories in /dev contain terminal-related device files
and should be searched first. These subdirectory names must appear
on separate lines and must begin with /dev. Those path names that do
not begin with /dev will be ignored and a warning will be sent to the
console. Blank lines (lines containing only white space) and lines
beginning with the comment character "#" will be ignored. For each
file listed (except for the special entry /dev), ttyname will
recursively search through subdirectories looking for a match. If
/dev appears in the ttysrch file, the /dev directory itself will be
searched but there will not be a recursive search through its
subdirectories.


When ttyname searches through the device files, it tries to find a
file whose major/minor device number, file system identifier, and
inode number match that of the file descriptor it was given as an
argument. If a match is not found, it will settle for a match of just
major/minor device and file system identifier, if one can be found.
However, if the file descriptor is associated with a cloned device,
this algorithm does not work efficiently because the inode number of
the device file associated with a clonable device will never match
the inode number of the file descriptor that was returned by the open
of that clonable device. To help with these situations, entries can
be put into the /etc/ttysrch file to improve performance when cloned
devices are used as terminals on a system (for example, for remote
login). However, this is only useful if the minor devices related to
a cloned device are put into a subdirectory. (It is important to note
that device files need not exist for cloned devices and if that is
the case, ttyname will eventually fail.) An optional second field is
used in the /etc/ttysrch file to indicate the matching criteria. This
field is separated by white space (any combination of blanks or
tabs). The letter M means major/minor device number, F means file
system identifier, and I means inode number. If this field is not
specified for an entry, the default is MFI which means try to match
on all three. For cloned devices the field should be MF, which
indicates that it is not necessary to match on the inode number.


Without the /etc/ttysrch file, ttyname will search the /dev directory
by first looking in the directories /dev/term, /dev/pts, and /dev/xt.
If a system has terminal devices installed in directories other than
these, it may help performance if the ttysrch file is created and
contains that list of directories.

EXAMPLES

Example 1: A sample display of /etc/ttysrch command.

A sample /etc/ttysrch file follows:


/dev/term MFI
/dev/pts MFI
/dev/xt MFI
/dev/slan MF


This file tells ttyname that it should first search through those
directories listed and that when searching through the /dev/slan
directory, if a file is encountered whose major/minor devices and
file system identifier match that of the file descriptor argument to
ttyname, this device name should be considered a match.

FILES

/etc/ttysrch

SEE ALSO

ttyname(3C)

February 23, 1994 TTYSRCH(5)