Paging Screen Output (GNU Octave (version 6.4.0))

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#### 14.1.1.1 Paging Screen Output

When running interactively, Octave normally sends all output directly to the Command Window. However, when using the CLI version of Octave this can create a problem because large volumes of data will stream by before you can read them. In such cases, it is better to use a paging program such as `less` or `more` which displays just one screenful at a time. With `less` (and some versions of `more`) you can also scan forward and backward, and search for specific items. The pager is enabled by the command `more on`.

Normally, no output is displayed by the pager until just before Octave is ready to print the top level prompt, or read from the standard input (for example, by using the `fscanf` or `scanf` functions). This means that there may be some delay before any output appears on your screen if you have asked Octave to perform a significant amount of work with a single command statement. The function `fflush` may be used to force output to be sent to the pager (or any other stream) immediately.

You can select the program to run as the pager with the `PAGER` function, and configure the pager itself with the `PAGER_FLAGS` function.

: more
: more on
: more off

  Turn output pagination on or off.

  Without an argument, `more` toggles the current state.

  The current state can be determined via `page_screen_output`.

  See also: page_screen_output, page_output_immediately, PAGER, PAGER_FLAGS.

: val = PAGER ()
: old_val = PAGER (new_val)
: PAGER (new_val, "local")

  Query or set the internal variable that specifies the program to use to display terminal output on your system.

  The default value is normally `"less"`, `"more"`, or `"pg"`, depending on what programs are installed on your system. See Installation.

  When called from inside a function with the `"local"` option, the variable is changed locally for the function and any subroutines it calls. The original variable value is restored when exiting the function.

  See also: PAGER_FLAGS, page_output_immediately, more, page_screen_output.

: val = PAGER_FLAGS ()
: old_val = PAGER_FLAGS (new_val)
: PAGER_FLAGS (new_val, "local")

  Query or set the internal variable that specifies the options to pass to the pager.

  When called from inside a function with the `"local"` option, the variable is changed locally for the function and any subroutines it calls. The original variable value is restored when exiting the function.

  See also: PAGER, more, page_screen_output, page_output_immediately.

: val = page_screen_output ()
: old_val = page_screen_output (new_val)
: page_screen_output (new_val, "local")

  Query or set the internal variable that controls whether output intended for the terminal window that is longer than one page is sent through a pager.

  This allows you to view one screenful at a time. Some pagers (such as `less`—see Installation) are also capable of moving backward on the output.

  When called from inside a function with the `"local"` option, the variable is changed locally for the function and any subroutines it calls. The original variable value is restored when exiting the function.

  See also: more, page_output_immediately, PAGER, PAGER_FLAGS.

: val = page_output_immediately ()
: old_val = page_output_immediately (new_val)
: page_output_immediately (new_val, "local")

  Query or set the internal variable that controls whether Octave sends output to the pager as soon as it is available.

  When the value is `false`, Octave buffers its output and waits until just before the prompt is printed to flush it to the pager. This is the default.

  When `page_screen_output` is `false`, this variable has no effect.

  When called from inside a function with the `"local"` option, the variable is changed locally for the function and any subroutines it calls. The original variable value is restored when exiting the function.

  See also: page_screen_output, more, PAGER, PAGER_FLAGS.

: fflush (fid)

  Flush output to file descriptor fid.

  `fflush` returns 0 on success and an OS dependent error value (-1 on Unix) on error.

  Programming Note: Flushing is useful for ensuring that all pending output makes it to the screen before some other event occurs. For example, it is always a good idea to flush the standard output stream before calling `input`.

  See also: fopen, fclose.

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