IO Channels

IO Channels — portable support for using files, pipes and sockets

Synopsis


#include <glib.h>

                    GIOChannel;

GIOChannel*         g_io_channel_unix_new               (int fd);
gint                g_io_channel_unix_get_fd            (GIOChannel *channel);
GIOChannel*         g_io_channel_win32_new_fd           (gint fd);
GIOChannel*         g_io_channel_win32_new_socket       (gint socket);
GIOChannel*         g_io_channel_win32_new_messages     (guint hwnd);

void                g_io_channel_init                   (GIOChannel *channel);

GIOChannel*         g_io_channel_new_file               (const gchar *filename,
                                                         const gchar *mode,
                                                         GError **error);
GIOStatus           g_io_channel_read_chars             (GIOChannel *channel,
                                                         gchar *buf,
                                                         gsize count,
                                                         gsize *bytes_read,
                                                         GError **error);
GIOStatus           g_io_channel_read_unichar           (GIOChannel *channel,
                                                         gunichar *thechar,
                                                         GError **error);
GIOStatus           g_io_channel_read_line              (GIOChannel *channel,
                                                         gchar **str_return,
                                                         gsize *length,
                                                         gsize *terminator_pos,
                                                         GError **error);
GIOStatus           g_io_channel_read_line_string       (GIOChannel *channel,
                                                         GString *buffer,
                                                         gsize *terminator_pos,
                                                         GError **error);
GIOStatus           g_io_channel_read_to_end            (GIOChannel *channel,
                                                         gchar **str_return,
                                                         gsize *length,
                                                         GError **error);
GIOStatus           g_io_channel_write_chars            (GIOChannel *channel,
                                                         const gchar *buf,
                                                         gssize count,
                                                         gsize *bytes_written,
                                                         GError **error);
GIOStatus           g_io_channel_write_unichar          (GIOChannel *channel,
                                                         gunichar thechar,
                                                         GError **error);
GIOStatus           g_io_channel_flush                  (GIOChannel *channel,
                                                         GError **error);
GIOStatus           g_io_channel_seek_position          (GIOChannel *channel,
                                                         gint64 offset,
                                                         GSeekType type,
                                                         GError **error);
enum                GSeekType;
GIOStatus           g_io_channel_shutdown               (GIOChannel *channel,
                                                         gboolean flush,
                                                         GError **err);

enum                GIOStatus;
enum                GIOChannelError;
#define             G_IO_CHANNEL_ERROR
GIOChannelError     g_io_channel_error_from_errno       (gint en);

GIOChannel*         g_io_channel_ref                    (GIOChannel *channel);
void                g_io_channel_unref                  (GIOChannel *channel);

GSource*            g_io_create_watch                   (GIOChannel *channel,
                                                         GIOCondition condition);
guint               g_io_add_watch                      (GIOChannel *channel,
                                                         GIOCondition condition,
                                                         GIOFunc func,
                                                         gpointer user_data);
guint               g_io_add_watch_full                 (GIOChannel *channel,
                                                         gint priority,
                                                         GIOCondition condition,
                                                         GIOFunc func,
                                                         gpointer user_data,
                                                         GDestroyNotify notify);
enum                GIOCondition;
gboolean            (*GIOFunc)                          (GIOChannel *source,
                                                         GIOCondition condition,
                                                         gpointer data);

                    GIOFuncs;

gsize               g_io_channel_get_buffer_size        (GIOChannel *channel);
void                g_io_channel_set_buffer_size        (GIOChannel *channel,
                                                         gsize size);
GIOCondition        g_io_channel_get_buffer_condition   (GIOChannel *channel);
GIOFlags            g_io_channel_get_flags              (GIOChannel *channel);
GIOStatus           g_io_channel_set_flags              (GIOChannel *channel,
                                                         GIOFlags flags,
                                                         GError **error);
enum                GIOFlags;
const gchar*        g_io_channel_get_line_term          (GIOChannel *channel,
                                                         gint *length);
void                g_io_channel_set_line_term          (GIOChannel *channel,
                                                         const gchar *line_term,
                                                         gint length);
gboolean            g_io_channel_get_buffered           (GIOChannel *channel);
void                g_io_channel_set_buffered           (GIOChannel *channel,
                                                         gboolean buffered);
const gchar*        g_io_channel_get_encoding           (GIOChannel *channel);
GIOStatus           g_io_channel_set_encoding           (GIOChannel *channel,
                                                         const gchar *encoding,
                                                         GError **error);
gboolean            g_io_channel_get_close_on_unref     (GIOChannel *channel);
void                g_io_channel_set_close_on_unref     (GIOChannel *channel,
                                                         gboolean do_close);


GIOError            g_io_channel_read                   (GIOChannel *channel,
                                                         gchar *buf,
                                                         gsize count,
                                                         gsize *bytes_read);
enum                GIOError;
GIOError            g_io_channel_write                  (GIOChannel *channel,
                                                         const gchar *buf,
                                                         gsize count,
                                                         gsize *bytes_written);
GIOError            g_io_channel_seek                   (GIOChannel *channel,
                                                         gint64 offset,
                                                         GSeekType type);
void                g_io_channel_close                  (GIOChannel *channel);

Description

The GIOChannel data type aims to provide a portable method for using file descriptors, pipes, and sockets, and integrating them into the main event loop. Currently full support is available on UNIX platforms, support for Windows is only partially complete.

To create a new GIOChannel on UNIX systems use g_io_channel_unix_new(). This works for plain file descriptors, pipes and sockets. Alternatively, a channel can be created for a file in a system independent manner using g_io_channel_new_file().

Once a GIOChannel has been created, it can be used in a generic manner with the functions g_io_channel_read_chars(), g_io_channel_write_chars(), g_io_channel_seek_position(), and g_io_channel_shutdown().

To add a GIOChannel to the main event loop use g_io_add_watch() or g_io_add_watch_full(). Here you specify which events you are interested in on the GIOChannel, and provide a function to be called whenever these events occur.

GIOChannel instances are created with an initial reference count of 1. g_io_channel_ref() and g_io_channel_unref() can be used to increment or decrement the reference count respectively. When the reference count falls to 0, the GIOChannel is freed. (Though it isn't closed automatically, unless it was created using g_io_channel_new_from_file().) Using g_io_add_watch() or g_io_add_watch_full() increments a channel's reference count.

The new functions g_io_channel_read_chars(), g_io_channel_read_line(), g_io_channel_read_line_string(), g_io_channel_read_to_end(), g_io_channel_write_chars(), g_io_channel_seek_position(), and g_io_channel_flush() should not be mixed with the deprecated functions g_io_channel_read(), g_io_channel_write(), and g_io_channel_seek() on the same channel.

Details

GIOChannel

typedef struct {
} GIOChannel;

A data structure representing an IO Channel. The fields should be considered private and should only be accessed with the following functions.


g_io_channel_unix_new ()

GIOChannel*         g_io_channel_unix_new               (int fd);

Creates a new GIOChannel given a file descriptor. On UNIX systems this works for plain files, pipes, and sockets.

The returned GIOChannel has a reference count of 1.

The default encoding for GIOChannel is UTF-8. If your application is reading output from a command using via pipe, you may need to set the encoding to the encoding of the current locale (see g_get_charset()) with the g_io_channel_set_encoding() function.

If you want to read raw binary data without interpretation, then call the g_io_channel_set_encoding() function with NULL for the encoding argument.

This function is available in GLib on Windows, too, but you should avoid using it on Windows. The domain of file descriptors and sockets overlap. There is no way for GLib to know which one you mean in case the argument you pass to this function happens to be both a valid file descriptor and socket. If that happens a warning is issued, and GLib assumes that it is the file descriptor you mean.

fd :

a file descriptor.

Returns :

a new GIOChannel.

g_io_channel_unix_get_fd ()

gint                g_io_channel_unix_get_fd            (GIOChannel *channel);

Returns the file descriptor of the GIOChannel.

On Windows this function returns the file descriptor or socket of the GIOChannel.

channel :

a GIOChannel, created with g_io_channel_unix_new().

Returns :

the file descriptor of the GIOChannel.

g_io_channel_win32_new_fd ()

GIOChannel*         g_io_channel_win32_new_fd           (gint fd);

Creates a new GIOChannel given a file descriptor on Windows. This works for file descriptors from the C runtime.

This function works for file descriptors as returned by the open(), creat(), pipe() and fileno() calls in the Microsoft C runtime. In order to meaningfully use this function your code should use the same C runtime as GLib uses, which is msvcrt.dll. Note that in current Microsoft compilers it is near impossible to convince it to build code that would use msvcrt.dll. The last Microsoft compiler version that supported using msvcrt.dll as the C runtime was version 6. The GNU compiler and toolchain for Windows, also known as Mingw, fully supports msvcrt.dll.

If you have created a GIOChannel for a file descriptor and started watching (polling) it, you shouldn't call read() on the file descriptor. This is because adding polling for a file descriptor is implemented in GLib on Windows by starting a thread that sits blocked in a read() from the file descriptor most of the time. All reads from the file descriptor should be done by this internal GLib thread. Your code should call only g_io_channel_read().

This function is available only in GLib on Windows.

fd :

a C library file descriptor.

Returns :

a new GIOChannel.

g_io_channel_win32_new_socket ()

GIOChannel*         g_io_channel_win32_new_socket       (gint socket);

Creates a new GIOChannel given a socket on Windows.

This function works for sockets created by Winsock. It's available only in GLib on Windows.

Polling a GSource created to watch a channel for a socket puts the socket in non-blocking mode. This is a side-effect of the implementation and unavoidable.

socket :

a Winsock socket

Returns :

a new GIOChannel

g_io_channel_win32_new_messages ()

GIOChannel*         g_io_channel_win32_new_messages     (guint hwnd);

Creates a new GIOChannel given a window handle on Windows.

This function creates a GIOChannel that can be used to poll for Windows messages for the window in question.

hwnd :

a window handle.

Returns :

a new GIOChannel.

g_io_channel_init ()

void                g_io_channel_init                   (GIOChannel *channel);

Initializes a GIOChannel struct. This is called by each of the above functions when creating a GIOChannel, and so is not often needed by the application programmer (unless you are creating a new type of GIOChannel).

channel :

a GIOChannel

g_io_channel_new_file ()

GIOChannel*         g_io_channel_new_file               (const gchar *filename,
                                                         const gchar *mode,
                                                         GError **error);

Open a file filename as a GIOChannel using mode mode. This channel will be closed when the last reference to it is dropped, so there is no need to call g_io_channel_close() (though doing so will not cause problems, as long as no attempt is made to access the channel after it is closed).

filename :

A string containing the name of a file

mode :

One of "r", "w", "a", "r+", "w+", "a+". These have the same meaning as in fopen()

error :

A location to return an error of type G_FILE_ERROR

Returns :

A GIOChannel on success, NULL on failure.

g_io_channel_read_chars ()

GIOStatus           g_io_channel_read_chars             (GIOChannel *channel,
                                                         gchar *buf,
                                                         gsize count,
                                                         gsize *bytes_read,
                                                         GError **error);

Replacement for g_io_channel_read() with the new API.

channel :

a GIOChannel

buf :

a buffer to read data into

count :

the size of the buffer. Note that the buffer may not be complelely filled even if there is data in the buffer if the remaining data is not a complete character.

bytes_read :

The number of bytes read. This may be zero even on success if count < 6 and the channel's encoding is non-NULL. This indicates that the next UTF-8 character is too wide for the buffer.

error :

a location to return an error of type GConvertError or GIOChannelError.

Returns :

the status of the operation.

g_io_channel_read_unichar ()

GIOStatus           g_io_channel_read_unichar           (GIOChannel *channel,
                                                         gunichar *thechar,
                                                         GError **error);

Reads a Unicode character from channel. This function cannot be called on a channel with NULL encoding.

channel :

a GIOChannel

thechar :

a location to return a character

error :

a location to return an error of type GConvertError or GIOChannelError

Returns :

a GIOStatus

g_io_channel_read_line ()

GIOStatus           g_io_channel_read_line              (GIOChannel *channel,
                                                         gchar **str_return,
                                                         gsize *length,
                                                         gsize *terminator_pos,
                                                         GError **error);

Reads a line, including the terminating character(s), from a GIOChannel into a newly-allocated string. str_return will contain allocated memory if the return is G_IO_STATUS_NORMAL.

channel :

a GIOChannel

str_return :

The line read from the GIOChannel, including the line terminator. This data should be freed with g_free() when no longer needed. This is a nul-terminated string. If a length of zero is returned, this will be NULL instead.

length :

location to store length of the read data, or NULL

terminator_pos :

location to store position of line terminator, or NULL

error :

A location to return an error of type GConvertError or GIOChannelError

Returns :

the status of the operation.

g_io_channel_read_line_string ()

GIOStatus           g_io_channel_read_line_string       (GIOChannel *channel,
                                                         GString *buffer,
                                                         gsize *terminator_pos,
                                                         GError **error);

Reads a line from a GIOChannel, using a GString as a buffer.

channel :

a GIOChannel

buffer :

a GString into which the line will be written. If buffer already contains data, the old data will be overwritten.

terminator_pos :

location to store position of line terminator, or NULL

error :

a location to store an error of type GConvertError or GIOChannelError

Returns :

the status of the operation.

g_io_channel_read_to_end ()

GIOStatus           g_io_channel_read_to_end            (GIOChannel *channel,
                                                         gchar **str_return,
                                                         gsize *length,
                                                         GError **error);

Reads all the remaining data from the file.

channel :

a GIOChannel

str_return :

Location to store a pointer to a string holding the remaining data in the GIOChannel. This data should be freed with g_free() when no longer needed. This data is terminated by an extra nul character, but there may be other nuls in the intervening data.

length :

location to store length of the data

error :

location to return an error of type GConvertError or GIOChannelError

Returns :

G_IO_STATUS_NORMAL on success. This function never returns G_IO_STATUS_EOF.

g_io_channel_write_chars ()

GIOStatus           g_io_channel_write_chars            (GIOChannel *channel,
                                                         const gchar *buf,
                                                         gssize count,
                                                         gsize *bytes_written,
                                                         GError **error);

Replacement for g_io_channel_write() with the new API.

On seekable channels with encodings other than NULL or UTF-8, generic mixing of reading and writing is not allowed. A call to g_io_channel_write_chars() may only be made on a channel from which data has been read in the cases described in the documentation for g_io_channel_set_encoding().

channel :

a GIOChannel

buf :

a buffer to write data from

count :

the size of the buffer. If -1, the buffer is taken to be a nul-terminated string.

bytes_written :

The number of bytes written. This can be nonzero even if the return value is not G_IO_STATUS_NORMAL. If the return value is G_IO_STATUS_NORMAL and the channel is blocking, this will always be equal to count if count >= 0.

error :

a location to return an error of type GConvertError or GIOChannelError

Returns :

the status of the operation.

g_io_channel_write_unichar ()

GIOStatus           g_io_channel_write_unichar          (GIOChannel *channel,
                                                         gunichar thechar,
                                                         GError **error);

Writes a Unicode character to channel. This function cannot be called on a channel with NULL encoding.

channel :

a GIOChannel

thechar :

a character

error :

location to return an error of type GConvertError or GIOChannelError

Returns :

a GIOStatus

g_io_channel_flush ()

GIOStatus           g_io_channel_flush                  (GIOChannel *channel,
                                                         GError **error);

Flushes the write buffer for the GIOChannel.

channel :

a GIOChannel

error :

location to store an error of type GIOChannelError

Returns :

the status of the operation: One of G_IO_CHANNEL_NORMAL, G_IO_CHANNEL_AGAIN, or G_IO_CHANNEL_ERROR.

g_io_channel_seek_position ()

GIOStatus           g_io_channel_seek_position          (GIOChannel *channel,
                                                         gint64 offset,
                                                         GSeekType type,
                                                         GError **error);

Replacement for g_io_channel_seek() with the new API.

channel :

a GIOChannel

offset :

The offset in bytes from the position specified by type

type :

a GSeekType. The type G_SEEK_CUR is only allowed in those cases where a call to g_io_channel_set_encoding() is allowed. See the documentation for g_io_channel_set_encoding() for details.

error :

A location to return an error of type GIOChannelError

Returns :

the status of the operation.

enum GSeekType

typedef enum
{
  G_SEEK_CUR,
  G_SEEK_SET,
  G_SEEK_END
} GSeekType;

An enumeration specifying the base position for a g_io_channel_seek_position() operation.

G_SEEK_CUR

the current position in the file.

G_SEEK_SET

the start of the file.

G_SEEK_END

the end of the file.

g_io_channel_shutdown ()

GIOStatus           g_io_channel_shutdown               (GIOChannel *channel,
                                                         gboolean flush,
                                                         GError **err);

Close an IO channel. Any pending data to be written will be flushed if flush is TRUE. The channel will not be freed until the last reference is dropped using g_io_channel_unref().

channel :

a GIOChannel

flush :

if TRUE, flush pending

err :

location to store a GIOChannelError

Returns :

the status of the operation.

enum GIOStatus

typedef enum
{
  G_IO_STATUS_ERROR,
  G_IO_STATUS_NORMAL,
  G_IO_STATUS_EOF,
  G_IO_STATUS_AGAIN
} GIOStatus;

Stati returned by most of the GIOFuncs functions.

G_IO_STATUS_ERROR

An error occurred.

G_IO_STATUS_NORMAL

Success.

G_IO_STATUS_EOF

End of file.

G_IO_STATUS_AGAIN

Resource temporarily unavailable.

enum GIOChannelError

typedef enum
{
  /* Derived from errno */
  G_IO_CHANNEL_ERROR_FBIG,
  G_IO_CHANNEL_ERROR_INVAL,
  G_IO_CHANNEL_ERROR_IO,
  G_IO_CHANNEL_ERROR_ISDIR,
  G_IO_CHANNEL_ERROR_NOSPC,
  G_IO_CHANNEL_ERROR_NXIO,
  G_IO_CHANNEL_ERROR_OVERFLOW,
  G_IO_CHANNEL_ERROR_PIPE,
  /* Other */
  G_IO_CHANNEL_ERROR_FAILED
} GIOChannelError;

Error codes returned by GIOChannel operations.

G_IO_CHANNEL_ERROR_FBIG

File too large.

G_IO_CHANNEL_ERROR_INVAL

Invalid argument.

G_IO_CHANNEL_ERROR_IO

IO error.

G_IO_CHANNEL_ERROR_ISDIR

File is a directory.

G_IO_CHANNEL_ERROR_NOSPC

No space left on device.

G_IO_CHANNEL_ERROR_NXIO

No such device or address.

G_IO_CHANNEL_ERROR_OVERFLOW

Value too large for defined datatype.

G_IO_CHANNEL_ERROR_PIPE

Broken pipe.

G_IO_CHANNEL_ERROR_FAILED

Some other error.

G_IO_CHANNEL_ERROR

#define G_IO_CHANNEL_ERROR g_io_channel_error_quark()

Error domain for GIOChannel operations. Errors in this domain will be from the GIOChannelError enumeration. See GError for information on error domains.


g_io_channel_error_from_errno ()

GIOChannelError     g_io_channel_error_from_errno       (gint en);

Converts an errno error number to a GIOChannelError.

en :

an errno error number, e.g. EINVAL

Returns :

a GIOChannelError error number, e.g. G_IO_CHANNEL_ERROR_INVAL.

g_io_channel_ref ()

GIOChannel*         g_io_channel_ref                    (GIOChannel *channel);

Increments the reference count of a GIOChannel.

channel :

a GIOChannel.

Returns :

the channel that was passed in (since 2.6)

g_io_channel_unref ()

void                g_io_channel_unref                  (GIOChannel *channel);

Decrements the reference count of a GIOChannel.

channel :

a GIOChannel.

g_io_create_watch ()

GSource*            g_io_create_watch                   (GIOChannel *channel,
                                                         GIOCondition condition);

Creates a GSource that's dispatched when condition is met for the given channel. For example, if condition is G_IO_IN, the source will be dispatched when there's data available for reading. g_io_add_watch() is a simpler interface to this same functionality, for the case where you want to add the source to the default main loop at the default priority.

On Windows, polling a GSource created to watch a channel for a socket puts the socket in non-blocking mode. This is a side-effect of the implementation and unavoidable.

channel :

a GIOChannel to watch

condition :

conditions to watch for

Returns :

a new GSource

g_io_add_watch ()

guint               g_io_add_watch                      (GIOChannel *channel,
                                                         GIOCondition condition,
                                                         GIOFunc func,
                                                         gpointer user_data);

Adds the GIOChannel into the main event loop with the default priority.

channel :

a GIOChannel

condition :

the condition to watch for

func :

the function to call when the condition is satisfied

user_data :

user data to pass to func

Returns :

the event source id

g_io_add_watch_full ()

guint               g_io_add_watch_full                 (GIOChannel *channel,
                                                         gint priority,
                                                         GIOCondition condition,
                                                         GIOFunc func,
                                                         gpointer user_data,
                                                         GDestroyNotify notify);

Adds the GIOChannel into the main event loop with the given priority.

channel :

a GIOChannel

priority :

the priority of the GIOChannel source

condition :

the condition to watch for

func :

the function to call when the condition is satisfied

user_data :

user data to pass to func

notify :

the function to call when the source is removed

Returns :

the event source id

enum GIOCondition

typedef enum
{
  G_IO_IN	GLIB_SYSDEF_POLLIN,
  G_IO_OUT	GLIB_SYSDEF_POLLOUT,
  G_IO_PRI	GLIB_SYSDEF_POLLPRI,
  G_IO_ERR	GLIB_SYSDEF_POLLERR,
  G_IO_HUP	GLIB_SYSDEF_POLLHUP,
  G_IO_NVAL	GLIB_SYSDEF_POLLNVAL
} GIOCondition;

A bitwise combination representing a condition to watch for on an event source.

G_IO_IN

There is data to read.

G_IO_OUT

Data can be written (without blocking).

G_IO_PRI

There is urgent data to read.

G_IO_ERR

Error condition.

G_IO_HUP

Hung up (the connection has been broken, usually for pipes and sockets).

G_IO_NVAL

Invalid request. The file descriptor is not open.

GIOFunc ()

gboolean            (*GIOFunc)                          (GIOChannel *source,
                                                         GIOCondition condition,
                                                         gpointer data);

Specifies the type of function passed to g_io_add_watch() or g_io_add_watch_full(), which is called when the requested condition on a GIOChannel is satisfied.

source :

the GIOChannel event source

condition :

the condition which has been satisfied

data :

user data set in g_io_add_watch() or g_io_add_watch_full()

Returns :

the function should return FALSE if the event source should be removed

GIOFuncs

typedef struct {
  GIOStatus (*io_read)           (GIOChannel   *channel, 
			          gchar        *buf, 
				  gsize         count,
				  gsize        *bytes_read,
				  GError      **err);
  GIOStatus (*io_write)          (GIOChannel   *channel, 
				  const gchar  *buf, 
				  gsize         count,
				  gsize        *bytes_written,
				  GError      **err);
  GIOStatus (*io_seek)           (GIOChannel   *channel, 
				  gint64        offset, 
				  GSeekType     type,
				  GError      **err);
  GIOStatus  (*io_close)         (GIOChannel   *channel,
				  GError      **err);
  GSource*   (*io_create_watch)  (GIOChannel   *channel,
				  GIOCondition  condition);
  void       (*io_free)          (GIOChannel   *channel);
  GIOStatus  (*io_set_flags)     (GIOChannel   *channel,
                                  GIOFlags      flags,
				  GError      **err);
  GIOFlags   (*io_get_flags)     (GIOChannel   *channel);
} GIOFuncs;

A table of functions used to handle different types of GIOChannel in a generic way.


g_io_channel_get_buffer_size ()

gsize               g_io_channel_get_buffer_size        (GIOChannel *channel);

Gets the buffer size.

channel :

a GIOChannel

Returns :

the size of the buffer.

g_io_channel_set_buffer_size ()

void                g_io_channel_set_buffer_size        (GIOChannel *channel,
                                                         gsize size);

Sets the buffer size.

channel :

a GIOChannel

size :

the size of the buffer, or 0 to let GLib pick a good size

g_io_channel_get_buffer_condition ()

GIOCondition        g_io_channel_get_buffer_condition   (GIOChannel *channel);

This function returns a GIOCondition depending on whether there is data to be read/space to write data in the internal buffers in the GIOChannel. Only the flags G_IO_IN and G_IO_OUT may be set.

channel :

A GIOChannel

Returns :

A GIOCondition

g_io_channel_get_flags ()

GIOFlags            g_io_channel_get_flags              (GIOChannel *channel);

Gets the current flags for a GIOChannel, including read-only flags such as G_IO_FLAG_IS_READABLE.

The values of the flags G_IO_FLAG_IS_READABLE and G_IO_FLAG_IS_WRITEABLE are cached for internal use by the channel when it is created. If they should change at some later point (e.g. partial shutdown of a socket with the UNIX shutdown() function), the user should immediately call g_io_channel_get_flags() to update the internal values of these flags.

channel :

a GIOChannel

Returns :

the flags which are set on the channel

g_io_channel_set_flags ()

GIOStatus           g_io_channel_set_flags              (GIOChannel *channel,
                                                         GIOFlags flags,
                                                         GError **error);

Sets the (writeable) flags in channel to (flags & G_IO_CHANNEL_SET_MASK).

channel :

a GIOChannel

flags :

the flags to set on the IO channel

error :

A location to return an error of type GIOChannelError

Returns :

the status of the operation.

enum GIOFlags

typedef enum
{
  G_IO_FLAG_APPEND = 1 << 0,
  G_IO_FLAG_NONBLOCK = 1 << 1,
  G_IO_FLAG_IS_READABLE = 1 << 2,	/* Read only flag */
  G_IO_FLAG_IS_WRITEABLE = 1 << 3,	/* Read only flag */
  G_IO_FLAG_IS_SEEKABLE = 1 << 4,	/* Read only flag */
  G_IO_FLAG_MASK = (1 << 5) - 1,
  G_IO_FLAG_GET_MASK = G_IO_FLAG_MASK,
  G_IO_FLAG_SET_MASK = G_IO_FLAG_APPEND | G_IO_FLAG_NONBLOCK
} GIOFlags;

Specifies properties of a GIOChannel. Some of the flags can only be read with g_io_channel_get_flags(), but not changed with g_io_channel_set_flags().

G_IO_FLAG_APPEND

turns on append mode, corresponds to O_APPEND (see the documentation of the UNIX open() syscall).

G_IO_FLAG_NONBLOCK

turns on nonblocking mode, corresponds to O_NONBLOCK/O_NDELAY (see the documentation of the UNIX open() syscall).

G_IO_FLAG_IS_READABLE

indicates that the io channel is readable. This flag can not be changed.

G_IO_FLAG_IS_WRITEABLE

indicates that the io channel is writable. This flag can not be changed.

G_IO_FLAG_IS_SEEKABLE

indicates that the io channel is seekable, i.e. that g_io_channel_seek_position() can be used on it. This flag can not be changed.

G_IO_FLAG_MASK

G_IO_FLAG_GET_MASK

G_IO_FLAG_SET_MASK


g_io_channel_get_line_term ()

const gchar*        g_io_channel_get_line_term          (GIOChannel *channel,
                                                         gint *length);

This returns the string that GIOChannel uses to determine where in the file a line break occurs. A value of NULL indicates autodetection.

channel :

a GIOChannel

length :

a location to return the length of the line terminator

Returns :

The line termination string. This value is owned by GLib and must not be freed.

g_io_channel_set_line_term ()

void                g_io_channel_set_line_term          (GIOChannel *channel,
                                                         const gchar *line_term,
                                                         gint length);

This sets the string that GIOChannel uses to determine where in the file a line break occurs.

channel :

a GIOChannel

line_term :

The line termination string. Use NULL for autodetect. Autodetection breaks on "\n", "\r\n", "\r", "\0", and the Unicode paragraph separator. Autodetection should not be used for anything other than file-based channels.

length :

The length of the termination string. If -1 is passed, the string is assumed to be nul-terminated. This option allows termination strings with embedded nuls.

g_io_channel_get_buffered ()

gboolean            g_io_channel_get_buffered           (GIOChannel *channel);

Returns whether channel is buffered.

channel :

a GIOChannel

Returns :

TRUE if the channel is buffered.

g_io_channel_set_buffered ()

void                g_io_channel_set_buffered           (GIOChannel *channel,
                                                         gboolean buffered);

The buffering state can only be set if the channel's encoding is NULL. For any other encoding, the channel must be buffered.

A buffered channel can only be set unbuffered if the channel's internal buffers have been flushed. Newly created channels or channels which have returned G_IO_STATUS_EOF not require such a flush. For write-only channels, a call to g_io_channel_flush() is sufficient. For all other channels, the buffers may be flushed by a call to g_io_channel_seek_position(). This includes the possibility of seeking with seek type G_SEEK_CUR and an offset of zero. Note that this means that socket-based channels cannot be set unbuffered once they have had data read from them.

On unbuffered channels, it is safe to mix read and write calls from the new and old APIs, if this is necessary for maintaining old code.

The default state of the channel is buffered.

channel :

a GIOChannel

buffered :

whether to set the channel buffered or unbuffered

g_io_channel_get_encoding ()

const gchar*        g_io_channel_get_encoding           (GIOChannel *channel);

Gets the encoding for the input/output of the channel. The internal encoding is always UTF-8. The encoding NULL makes the channel safe for binary data.

channel :

a GIOChannel

Returns :

A string containing the encoding, this string is owned by GLib and must not be freed.

g_io_channel_set_encoding ()

GIOStatus           g_io_channel_set_encoding           (GIOChannel *channel,
                                                         const gchar *encoding,
                                                         GError **error);

Sets the encoding for the input/output of the channel. The internal encoding is always UTF-8. The default encoding for the external file is UTF-8.

The encoding NULL is safe to use with binary data.

The encoding can only be set if one of the following conditions is true:

Channels which do not meet one of the above conditions cannot call g_io_channel_seek_position() with an offset of G_SEEK_CUR, and, if they are "seekable", cannot call g_io_channel_write_chars() after calling one of the API "read" functions.

channel :

a GIOChannel

encoding :

the encoding type

error :

location to store an error of type GConvertError

Returns :

G_IO_STATUS_NORMAL if the encoding was successfully set.

g_io_channel_get_close_on_unref ()

gboolean            g_io_channel_get_close_on_unref     (GIOChannel *channel);

Returns whether the file/socket/whatever associated with channel will be closed when channel receives its final unref and is destroyed. The default value of this is TRUE for channels created by g_io_channel_new_file(), and FALSE for all other channels.

channel :

a GIOChannel.

Returns :

Whether the channel will be closed on the final unref of the GIOChannel data structure.

g_io_channel_set_close_on_unref ()

void                g_io_channel_set_close_on_unref     (GIOChannel *channel,
                                                         gboolean do_close);

Setting this flag to TRUE for a channel you have already closed can cause problems.

channel :

a GIOChannel

do_close :

Whether to close the channel on the final unref of the GIOChannel data structure. The default value of this is TRUE for channels created by g_io_channel_new_file(), and FALSE for all other channels.

g_io_channel_read ()

GIOError            g_io_channel_read                   (GIOChannel *channel,
                                                         gchar *buf,
                                                         gsize count,
                                                         gsize *bytes_read);

Warning

g_io_channel_read has been deprecated since version 2.2 and should not be used in newly-written code. Use g_io_channel_read_chars() instead.

Reads data from a GIOChannel.

channel :

a GIOChannel

buf :

a buffer to read the data into (which should be at least count bytes long)

count :

the number of bytes to read from the GIOChannel

bytes_read :

returns the number of bytes actually read

Returns :

G_IO_ERROR_NONE if the operation was successful.

enum GIOError

typedef enum
{
  G_IO_ERROR_NONE,
  G_IO_ERROR_AGAIN,
  G_IO_ERROR_INVAL,
  G_IO_ERROR_UNKNOWN
} GIOError;

GIOError is only used by the deprecated functions g_io_channel_read(), g_io_channel_write(), and g_io_channel_seek().

G_IO_ERROR_NONE

no error

G_IO_ERROR_AGAIN

an EAGAIN error occurred

G_IO_ERROR_INVAL

an EINVAL error occurred

G_IO_ERROR_UNKNOWN

another error occurred

g_io_channel_write ()

GIOError            g_io_channel_write                  (GIOChannel *channel,
                                                         const gchar *buf,
                                                         gsize count,
                                                         gsize *bytes_written);

Warning

g_io_channel_write has been deprecated since version 2.2 and should not be used in newly-written code. Use g_io_channel_write_chars() instead.

Writes data to a GIOChannel.

channel :

a GIOChannel

buf :

the buffer containing the data to write

count :

the number of bytes to write

bytes_written :

the number of bytes actually written

Returns :

G_IO_ERROR_NONE if the operation was successful.

g_io_channel_seek ()

GIOError            g_io_channel_seek                   (GIOChannel *channel,
                                                         gint64 offset,
                                                         GSeekType type);

Warning

g_io_channel_seek has been deprecated since version 2.2 and should not be used in newly-written code. Use g_io_channel_seek_position() instead.

Sets the current position in the GIOChannel, similar to the standard library function fseek().

channel :

a GIOChannel

offset :

an offset, in bytes, which is added to the position specified by type

type :

the position in the file, which can be G_SEEK_CUR (the current position), G_SEEK_SET (the start of the file), or G_SEEK_END (the end of the file)

Returns :

G_IO_ERROR_NONE if the operation was successful.

g_io_channel_close ()

void                g_io_channel_close                  (GIOChannel *channel);

Warning

g_io_channel_close has been deprecated since version 2.2 and should not be used in newly-written code. Use g_io_channel_shutdown() instead.

Close an IO channel. Any pending data to be written will be flushed, ignoring errors. The channel will not be freed until the last reference is dropped using g_io_channel_unref().

channel :

A GIOChannel

See Also

gtk_input_add_full(), gtk_input_remove(), gdk_input_add(), gdk_input_add_full(), gdk_input_remove()

Convenience functions for creating GIOChannel instances and adding them to the main event loop.