save a struct Post: 57492

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Top Forums Programming save a struct Post 57492 by AbEnd on Friday 29th of October 2004 11:31:54 AM

10-29-2004

Registered User

Yeah, you can.

Say you have a struct variable named s. You could simply write/read from ((void*)&s) to (((void*)&s) + sizeof s) using whatever I/O functions. But there are 2 problems with that.

1) Some compilers will produce code that use "sparse" structs. structs with holes in them, that is. This is to make the code faster. Memory accesses that is aligned at some power of 2 multiple is usually faster, for example. If the compiler or compiler settings were to change, the sparseness may change too and old data files would become incompatible.

2) This method will create data files that are architecture-dependent. Fundamental C types, like pointers, ints, floats, etc, won't read/write the same on different architecture. So the data files will not be portable.

So it would be better to encode your data in a standard way. There are a few ways to do that:

1) Just read/write your stuff using ASCII printable chars. You could use scanf(3)/printf(3) for that.

2) Check xdr(3) (eXternal Data Representation); that's what is used for rpc(3) (Remote Procedure Call). It can encode/decode your stuff automatically.

3) Use some library that uses XML format. That's the current hype.

AbEnd

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LEARN ABOUT SUNOS

gnome-session-save

gnome-session-save(1)						   User Commands					     gnome-session-save(1)

NAME

       gnome-session-save - saves or terminates the current GNOME session

SYNOPSIS

       gnome-session-save [--kill] [--gui] [gnome-std-options]

DESCRIPTION

       gnome-session-save can be used from a GNOME session to save a snapshot of the currently running applications. This session will be restored
       at your next GNOME startup session.

OPTIONS

       The following options are supported:

       --gui	       Shows a dialog when the session is saved, and reports errors in dialog boxes instead of printing to stderr.

       --kill	       Terminates the GNOME session.

       gnome-std-optionStandard options available for use with most GNOME applications.  See gnome-std-options(5) for more information.

EXAMPLES

       Example 1: Saving the user's current session

       example% gnome-session-save

       Example 2: Terminating the user's current session

       example% gnome-session-save --kill

       Example 3: Using the GUI to terminate the user's current session

       example% gnome-session-save --kill --gui

EXIT STATUS

       The following exit values are returned:

       0	Application exited successfully

       >0	Application exited with failure

FILES

       The following files are used by this application:

       /usr/bin/gnome-session-sThe command-line executable for the application.

ATTRIBUTES

       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Availability		     |SUNWgnome-session 	   |
       +-----------------------------+-----------------------------+
       |Interface stability	     |External			   |
       +-----------------------------+-----------------------------+

SEE ALSO

       gnome-std-options(5), default.session(5), gnome-smproxy(1), gnome-session(1)

NOTES

       Written by Brian Cameron, Sun Microsystems  Inc., 2003.

SunOS 5.10							    13 Jan 2003 					     gnome-session-save(1)

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