GIO provides a modern, easy-to-use VFS API 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 calls.[1] It ships with GLib as a separate library called libgio-2.0. It provides a file system abstraction which allows applications to access local and remote files with a single consistent API.
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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.
A simple example illustrating local file handling using GIO in C:
#include <glib/gprintf.h> #include <gio/gio.h> #define _g_free0(var) (var = (g_free (var), NULL)) #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 ("\ === file-description ===\n\ Content type: %s (%s)\n\ Size: %lluB\n\ === 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 using GCC and pkg-config, 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
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