Global Variables

  Glish makes available to every script the following global variables:

pi
      is an approximation of the mathematical constant , which equals the area of a unit circle. This global variable approximates to 24 decimal places.

e
      is an approximation of the mathematical constant e. The primary property of e is that if , then . This global variable approximates e to 24 decimal places.

argv
      is a list of the arguments (interpreted as string's) with which the Glish script was invoked. Presently the glish interpreter is invoked with a filename to interpret followed by a list of arguments. So, for example, if a script is invoked using:  

    glish script.g hello, how are you

then argv will be a string value with 4 elements, ``hello,", ``how", ``are", and ``you".

environ
      is a record providing access to the Unix environment (i.e., what in C programs is accessible via   getenv()). Each environment variable corresponds to a string-valued field in the record. For example,

    environ.HOME

will return the value of the $HOME environment variable. Naturally this could also be referred to using:

    environ["HOME"]

  Changing the environ global does not presently affect the environment in which Glish clients are run.

system
              is an agent record that contains general information about the environment (not in an ``environment variable'' sense) in which the Glish script runs. It also generates events corresponding to changes in the environment.

The predefined fields of system are:

version
    gives the version level of the Glish interpreter. Presently this field's type is string, though it may change to double in the future to facilitate inequality comparisons like ``system.version >= 2.1".

is_script_client
    is true (T) if the Glish script is being run as a script client (§ 7.10, page ) and false (F) if not.

print.limit
allows the user to limit how much of Glish   values are output to the screen (see § 5.3.2, page ).

print.precision
allows the user to specify the number   of significant digits use to output floating point numbers (see § 5.3.1, page ).

tk
contains the Tk version number if Glish was   compiled with the Tk widgets (see § 10.8, page ).

path.include
path searched by include when attempting   to include a file (see § 4.14, page ).

path.bin.host
path searched when starting clients on   the machine host.

output.pager.exec
the executable to be started to handle paging of output, e.g. less or more.

output.pager.limit
the number of lines where paging begins. If set to 0 paging is always done, if set to -1 paging is never done.

output.log
place to log input and output (see § 8.2, page ).

output.ilog
place to log input (see § 8.2, page ).

output.olog
place to log output (see § 8.2, page ).

output.pager.log
place to log input and output (see § 8.2, page ).

pid
process id of the current Glish     interpreter.

ppid
process id of the current Glish     interpreter's parent process.

limits.max
contains the maximum values for     Glish's builtin (non-boolean) numeric types.

limits.min
contains the minimum values for     Glish's builtin (non-boolean) numeric types.

The events generated by system are:

connection_lost
        indicates the loss of the network connection to a remote host. The value of the event names the remote host. See § 14.2, page  for details as to when this event is generated.

connection_restored
        indicates the restoration of the network connection to a remote host. The value of the event names the remote host. See § 14.2, page  for details as to when this event is generated.

daemon_terminated
      indicates that a remote glishd daemon terminated (normally this indicates a problem or bug. See § 14.2, page  for details as to when this event is generated.

For example, the following checkpoints some local data whenever the network connection to the ``frontend'' host drops, and rolls back to the checkpoint when connectivity resumes:  

    whenever system->connection_lost do
        {
        if ( $value == "frontend" )
            do_local_checkpoint()
        }

    whenever system->connection_restored do
        {
        if ( $value == "frontend" )
            roll_back_to_checkpoint()
        }

script
      has one of two possible values. If the Glish script is being run as a client of another script, then script is an agent record (§ 7.2.2, page ) that can be used to receive events sent by the parent script, and send events to it. If the Glish script is running independently, then script will be the boolean value F.

See § 7.10, page  for details.