6.3.4 open

op(en)

Open a graphics device for pgplot output and makes it the current device. If the device is opened successfully, it becomes the selected device to which graphics output is directed until another device is selected (see 6.3.3) or the device is closed (see 6.3.2). Pgplot prompts for the device argument which should be one of the following:

(1)

A complete device specification of the form 'device/type' or 'file/type', where 'type' is one of the allowed PGPLOT device types (installation-dependent) and 'device' or 'file' is the name of a graphics device or disk file appropriate for this type. The 'device' or 'file' may contain '/' characters; the final '/' delimits the 'type'. If necessary to avoid ambiguity, the 'device' part of the string may be enclosed in double quotation marks.

(2)

A device specification of the form '/type', where 'type' is one of the allowed PGPLOT device types. PGPLOT supplies a default file or device name appropriate for this device type.

(3)

A device specification with '/type' omitted; in this case the type is taken from the environment variable PGPLOT_TYPE, if defined (e.g., setenv PGPLOT_TYPE PS). Because of possible confusion with '/' in file-names, omitting the device type in this way is not recommended.

(4)

A blank string (' '); in this case, PGOPEN will use the value of environment variable PGPLOT_DEV as the device specification, or '/NULL' if the environment variable is undefined.

(5)

A single question mark, with optional trailing spaces ('?'); in this case, PGPLOT will prompt the user to supply the device specification, with a prompt string of the form 'Graphics device/type (? to see list, default XXX):' where 'XXX' is the default (value of environment variable PGPLOT_DEV).

(6)

A non-blank string in which the first character is a question mark (e.g., '?Device: '); in this case, PGPLOT will prompt the user to supply the device specification, using the supplied string as the prompt (without the leading question mark but including any trailing spaces).

In cases (5) and (6), the device specification is read from the standard input. The user should respond to the prompt with a device specification of the form (1), (2), or (3). If the user types a question-mark in response to the prompt, a list of available device types is displayed and the prompt is re-issued. If the user supplies an invalid device specification, the prompt is re-issued. If the user responds with an end-of-file character, e.g., ctrl-D in UNIX, program execution is aborted; this avoids the possibility of an infinite prompting loop. A programmer should avoid use of PGPLOT-prompting if this behavior is not desirable.

The device type is case-insensitive (e.g., '/ps' and '/PS' are equivalent). The device or file name may be case-sensitive in some operating systems.

Examples of valid DEVICE arguments:

(1)

'plot.ps/ps', 'dir/plot.ps/ps', '"dir/plot.ps"/ps', 'user:[tjp.plots]plot.ps/PS'

(2)

'/ps' (PGPLOT interprets this as 'pgplot.ps/ps')

(3)

'plot.ps' (if PGPLOT_TYPE is defined as 'ps', PGPLOT interprets this as 'plot.ps/ps')

(4)

' ' (if PGPLOT_DEV is defined)

(5)

'? '

(6)

'?Device specification for PGPLOT: '