Cap

Section: User Contributed Perl Documentation (3)
Updated: 2021-01-27
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NAME

Term::Cap - Perl termcap interface

SYNOPSIS

    require Term::Cap;
    $terminal = Tgetent Term::Cap { TERM => undef, OSPEED => $ospeed };
    $terminal->Trequire(qw/ce ku kd/);
    $terminal->Tgoto('cm', $col, $row, $FH);
    $terminal->Tputs('dl', $count, $FH);
    $terminal->Tpad($string, $count, $FH);

DESCRIPTION

These are low-level functions to extract and use capabilities from a terminal capability (termcap) database.

More information on the terminal capabilities will be found in the termcap manpage on most Unix-like systems.

METHODS

The output strings for Tputs are cached for counts of 1 for performance. Tgoto and Tpad do not cache. "$self->{_xx}" is the raw termcap data and "$self->{xx}" is the cached version.

    print $terminal->Tpad($self->{_xx}, 1);

Tgoto, Tputs, and Tpad return the string and will also output the string to $FH if specified.

Tgetent

Returns a blessed object reference which the user can then use to send the control strings to the terminal using Tputs and Tgoto.

The function extracts the entry of the specified terminal type TERM (defaults to the environment variable TERM) from the database.

It will look in the environment for a TERMCAP variable. If found, and the value does not begin with a slash, and the terminal type name is the same as the environment string TERM, the TERMCAP string is used instead of reading a termcap file. If it does begin with a slash, the string is used as a path name of the termcap file to search. If TERMCAP does not begin with a slash and name is different from TERM, Tgetent searches the files $HOME/.termcap, /etc/termcap, and /usr/share/misc/termcap, in that order, unless the environment variable TERMPATH exists, in which case it specifies a list of file pathnames (separated by spaces or colons) to be searched instead. Whenever multiple files are searched and a tc field occurs in the requested entry, the entry it names must be found in the same file or one of the succeeding files. If there is a ":tc=...:" in the TERMCAP environment variable string it will continue the search in the files as above.

The extracted termcap entry is available in the object as "$self->{TERMCAP}".

It takes a hash reference as an argument with two optional keys:

OSPEED: The terminal output bit rate (often mistakenly called the baud rate) for this terminal - if not set a warning will be generated and it will be defaulted to 9600. OSPEED can be specified as either a POSIX termios/SYSV termio speeds (where 9600 equals 9600) or an old DSD-style speed ( where 13 equals 9600).
TERM: The terminal type whose termcap entry will be used - if not supplied it will default to $ENV{TERM}: if that is not set then Tgetent will croak.

: It calls "croak" on failure.

Tpad

Outputs a literal string with appropriate padding for the current terminal.

It takes three arguments:

$string: The literal string to be output. If it starts with a number and an optional '*' then the padding will be increased by an amount relative to this number, if the '*' is present then this amount will be multiplied by $cnt. This part of $string is removed before output/
$cnt: Will be used to modify the padding applied to string as described above.
$FH: An optional filehandle (or IO::Handle ) that output will be printed to.

: The padded $string is returned.

Tputs

Output the string for the given capability padded as appropriate without any parameter substitution.

It takes three arguments:

$cap: The capability whose string is to be output.
$cnt: A count passed to Tpad to modify the padding applied to the output string. If $cnt is zero or one then the resulting string will be cached.
$FH: An optional filehandle (or IO::Handle ) that output will be printed to.

: The appropriate string for the capability will be returned.

Tgoto

Tgoto decodes a cursor addressing string with the given parameters.

There are four arguments:

$cap: The name of the capability to be output.
$col: The first value to be substituted in the output string ( usually the column in a cursor addressing capability )
$row: The second value to be substituted in the output string (usually the row in cursor addressing capabilities)
$FH: An optional filehandle (or IO::Handle ) to which the output string will be printed.

Substitutions are made with $col and $row in the output string with the following sprintf() line formats:

 %%   output `%'
 %d   output value as in printf %d
 %2   output value as in printf %2d
 %3   output value as in printf %3d
 %.   output value as in printf %c
 %+x  add x to value, then do %.

 %>xy if value > x then add y, no output
 %r   reverse order of two parameters, no output
 %i   increment by one, no output
 %B   BCD (16*(value/10)) + (value%10), no output

 %n   exclusive-or all parameters with 0140 (Datamedia 2500)
 %D   Reverse coding (value - 2*(value%16)), no output (Delta Data)

The output string will be returned.

Trequire

Takes a list of capabilities as an argument and will croak if one is not found.

EXAMPLES

    use Term::Cap;

    # Get terminal output speed
    require POSIX;
    my $termios = new POSIX::Termios;
    $termios->getattr;
    my $ospeed = $termios->getospeed;

    # Old-style ioctl code to get ospeed:
    #     require 'ioctl.pl';
    #     ioctl(TTY,$TIOCGETP,$sgtty);
    #     ($ispeed,$ospeed) = unpack('cc',$sgtty);

    # allocate and initialize a terminal structure
    $terminal = Tgetent Term::Cap { TERM => undef, OSPEED => $ospeed };

    # require certain capabilities to be available
    $terminal->Trequire(qw/ce ku kd/);

    # Output Routines, if $FH is undefined these just return the string

    # Tgoto does the % expansion stuff with the given args
    $terminal->Tgoto('cm', $col, $row, $FH);

    # Tputs doesn't do any % expansion.
    $terminal->Tputs('dl', $count = 1, $FH);

COPYRIGHT AND LICENSE

This software is free software and can be modified and distributed under the same terms as Perl itself.

Please see the file README in the Perl source distribution for details of the Perl license.

AUTHOR

This module is part of the core Perl distribution and is also maintained for CPAN by Jonathan Stowe <jns@gellyfish.co.uk>.

The code is hosted on Github: https://github.com/jonathanstowe/Term-Cap please feel free to fork, submit patches etc, etc there.

Cap