GIO provides a modern, easy-to-use VFS

Virtual file system

A virtual file system or virtual filesystem switch is an abstraction layer on top of a more concrete file system. The purpose of a VFS is to allow client applications to access different types of concrete file systems in a uniform way...

 API

Application programming interface

An application programming interface is a source code based specification intended to be used as an interface by software components to communicate with each other...

 that sits at the right level in the library stack. The goal is to overcome the shortcomings of GnomeVFS and provide an API that is so good that developers prefer it over raw POSIX

POSIX

POSIX , an acronym for "Portable Operating System Interface", is a family of standards specified by the IEEE for maintaining compatibility between operating systems...

 calls. It ships with GLib

GLib

GLib is a cross-platform software utility library that began as part of the GTK+ project. However, before releasing version 2 of GTK+, the project's developers decided to separate non-GUI-specific code from the GTK+ platform, thus creating GLib as a separate product...

 as a separate library called libgio-2.0. It provides a file system abstraction

Virtual file system

A virtual file system or virtual filesystem switch is an abstraction layer on top of a more concrete file system. The purpose of a VFS is to allow client applications to access different types of concrete file systems in a uniform way...

 which allows applications to access local and remote files with a single consistent API.

Features

• The abstract file system model of GIO consists of a number of interfaces and base classes for I/O and files.
• There is a number of stream classes, similar to the input and output stream hierarchies that can be found in frameworks like Java.
• There are interfaces related to applications and the types of files they handle.
• There is a framework for storing and retrieving application settings.
• There is support for network programming, including name resolution, lowlevel socket APIs and highlevel client and server helper classes.
• There is support for connecting to D-Bus, sending and receiving messages, owning and watching bus names, and making objects available on the bus.

Beyond these, GIO provides facilities for file monitoring, asynchronous I/O and filename completion. In addition to the interfaces, GIO provides implementations for the local case. Implementations for various network file systems are provided by the GVFS package as loadable modules.

Example

A simple example illustrating local file handling using GIO in C:

1. include
2. include

1. define _g_free0(var) (var = (g_free (var), NULL))
2. define _g_object_unref0(var) ((var NULL) ? NULL : (var = (g_object_unref (var), NULL)))

void log_g_error(GError * e, int line) {
g_printerr ("** ERROR **: %s (domain: %s, code: %d) at %d\n",
e->message, g_quark_to_string (e->domain), e->code, line);
}

int main (int argc, char ** argv) {
g_type_init ;
if (argc < 2) {
g_message ("Usage: %s file-name", argv[0]);
return 1;
}
GFile* file = NULL;
GFileInfo* fileinfo = NULL;
GFileType filetype = G_FILE_TYPE_UNKNOWN;
const char* contenttype = NULL;
gchar* contenttype_desc = NULL;
GFileInputStream* fis = NULL;
GDataInputStream* dis = NULL;
gchar* line = NULL;
GError* inner_error = NULL;
int error_line = 0;
file = g_file_new_for_path (argv[1]);
fileinfo = g_file_query_info (file, "standard::*", G_FILE_QUERY_INFO_NONE, NULL, &inner_error);
if (inner_error NULL) {
filetype = g_file_info_get_file_type(fileinfo);
contenttype = g_file_info_get_attribute_string (fileinfo, G_FILE_ATTRIBUTE_STANDARD_CONTENT_TYPE);
contenttype_desc = g_content_type_get_description(contenttype);
g_printf ("\

description-end

\n\
", contenttype, contenttype_desc, g_file_info_get_attribute_uint64 (fileinfo, G_FILE_ATTRIBUTE_STANDARD_SIZE));
_g_free0 (contenttype_desc);
//_g_object_unref0 (fileinfo); //if you do this here, 'contenttype' gets destroyed.
switch (filetype) {
case G_FILE_TYPE_REGULAR:
case G_FILE_TYPE_SYMBOLIC_LINK:
if (!g_content_type_is_a(contenttype, "text/*")) {
g_printerr ("Not a text-based document.\n");
break;
}
fis = g_file_read (file, NULL, &inner_error);
if (inner_error != NULL) {
_g_object_unref0 (fis);
error_line = __LINE__;
break;
}
dis = g_data_input_stream_new (G_INPUT_STREAM(fis));
_g_object_unref0 (fis);
while (TRUE) {
line = g_data_input_stream_read_line (dis, NULL, NULL, &inner_error);
if (inner_error != NULL) {
_g_free0 (line);
error_line = __LINE__;
break;
}
if (line NULL)
break;
g_printf ("%s\n", line);
_g_free0 (line);
}
_g_object_unref0 (dis);
break;
case G_FILE_TYPE_DIRECTORY:
g_printerr ("** INFO: Can't read a directory.\n");
break;
case G_FILE_TYPE_SPECIAL:
g_printerr ("** INFO: It's a \"special\" file.\n");
break;
case G_FILE_TYPE_SHORTCUT:
g_printerr ("** INFO: The given file is a shortcut.\n");
break;
case G_FILE_TYPE_MOUNTABLE:
g_printerr ("** INFO: File is a mountable location.\n");
break;
case G_FILE_TYPE_UNKNOWN:
g_printerr ("** INFO: Unknown file type.\n");
break;
}
}

_g_object_unref0 (fileinfo);
_g_object_unref0 (file);
if (inner_error != NULL) {
log_g_error (inner_error, error_line);
g_clear_error (&inner_error);
return 1;
}
return 0;
}


The above program takes a filename as an argument at runtime, prints its content-type and size, and if the input file is text-based, prints its contents too.
To compile the above program in Linux

Linux

Linux is a Unix-like computer operating system assembled under the model of free and open source software development and distribution. The defining component of any Linux system is the Linux kernel, an operating system kernel first released October 5, 1991 by Linus Torvalds...

 using GCC

GNU Compiler Collection

The GNU Compiler Collection is a compiler system produced by the GNU Project supporting various programming languages. GCC is a key component of the GNU toolchain...

 and pkg-config

Pkg-config

pkg-config is computer software that provides a unified interface for querying installed libraries for the purpose of compiling software from its source code. pkg-config was originally designed for Linux but is now also available for the various BSDs, Microsoft Windows, Mac OS X, and Solaris.It...

, use:
gcc -Wall -g gio-example.c -o gio-example $(pkg-config --cflags --libs gio-2.0)
assuming the source file is gio-example.c.
To execute the output file, use:
./gio-example filename
External links

• GIO Reference Manual
• GIO ToDo List