www.delorie.com/gnu/docs/octave/octave_104.html

search

	Buy GNU books!

GNU Octave

13.1.3 Simple File I/O

The save and load commands allow data to be written to and read from disk files in various formats. The default format of files written by the save command can be controlled using the built-in variables default_save_format and save_precision.

Note that Octave can not yet save or load structure variables or any user-defined types.

Command: save options file v1 v2 ...

Save the named variables v1, v2, ... in the file file. The special filename `-' can be used to write the output to your terminal. If no variable names are listed, Octave saves all the variables in the current scope. Valid options for the save command are listed in the following table. Options that modify the output format override the format specified by the built-in variable default_save_format.

-ascii

Save the data in Octave's text data format.

-binary

Save the data in Octave's binary data format.

-float-binary

Save the data in Octave's binary data format but only using single precision. You should use this format only if you know that all the values to be saved can be represented in single precision.

-mat-binary

Save the data in MATLAB's binary data format.

-save-builtins

Force Octave to save the values of built-in variables too. By default, Octave does not save built-in variables.

The list of variables to save may include wildcard patterns containing the following special characters:

?

Match any single character.

*

Match zero or more characters.

[ list ]

Match the list of characters specified by list. If the first character is ! or ^, match all characters except those specified by list. For example, the pattern `[a-zA-Z]' will match all lower and upper case alphabetic characters.

Except when using the MATLAB binary data file format, saving global variables also saves the global status of the variable, so that if it is restored at a later time using `load', it will be restored as a global variable.

The command

save -binary data a b*

saves the variable `a' and all variables beginning with `b' to the file `data' in Octave's binary format.

There are two variables that modify the behavior of save and one that controls whether variables are saved when Octave exits unexpectedly.

Built-in Variable: crash_dumps_octave_core

If this variable is set to a nonzero value, Octave tries to save all current variables the the file "octave-core" if it crashes or receives a hangup, terminate or similar signal. The default value is 1.

Built-in Variable: default_save_format

This variable specifies the default format for the save command. It should have one of the following values: "ascii", "binary", float-binary, or "mat-binary". The initial default save format is Octave's text format.

Built-in Variable: save_precision

This variable specifies the number of digits to keep when saving data in text format. The default value is 17.

Command: load options file v1 v2 ...

Load the named variables from the file file. As with save, you may specify a list of variables and load will only extract those variables with names that match. For example, to restore the variables saved in the file `data', use the command

load data

Octave will refuse to overwrite existing variables unless you use the option `-force'.

If a variable that is not marked as global is loaded from a file when a global symbol with the same name already exists, it is loaded in the global symbol table. Also, if a variable is marked as global in a file and a local symbol exists, the local symbol is moved to the global symbol table and given the value from the file. Since it seems that both of these cases are likely to be the result of some sort of error, they will generate warnings.

The load command can read data stored in Octave's text and binary formats, and MATLAB's binary format. It will automatically detect the type of file and do conversion from different floating point formats (currently only IEEE big and little endian, though other formats may added in the future).

Valid options for load are listed in the following table.

-force

Force variables currently in memory to be overwritten by variables with the same name found in the file.

-ascii

Force Octave to assume the file is in Octave's text format.

-binary

Force Octave to assume the file is in Octave's binary format.

-mat-binary

Force Octave to assume the file is in MATLAB's binary format.