ttysrch(4M)                      DG/UX R4.11                     ttysrch(4M)


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 (see clone(7)), 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 (e.g. 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.)  For example, if /dev/starlan is a cloned device,
       there could be a subdirectory /dev/slan that contains files 0, 1, 2,
       etc.  that correspond to the minor devices of the starlan driver.  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 top level of
       the /dev directory, and will then recursively search /dev/pts,
       /dev/sxt, 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.

EXAMPLE
       A sample /etc/ttysrch file follows:

       /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), clone(7)


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