Miscellaneous Utility Functions

Miscellaneous Utility Functions — a selection of portable utility functions

Synopsis

#include <glib.h>

const gchar *       g_get_application_name              (void);
void                g_set_application_name              (const gchar *application_name);
gchar *             g_get_prgname                       (void);
void                g_set_prgname                       (const gchar *prgname);
gchar **            g_get_environ                       (void);
const gchar *       g_environ_getenv                    (gchar **envp,
                                                         const gchar *variable);
gchar **            g_environ_setenv                    (gchar **envp,
                                                         const gchar *variable,
                                                         const gchar *value,
                                                         gboolean overwrite);
gchar **            g_environ_unsetenv                  (gchar **envp,
                                                         const gchar *variable);
const gchar *       g_getenv                            (const gchar *variable);
gboolean            g_setenv                            (const gchar *variable,
                                                         const gchar *value,
                                                         gboolean overwrite);
void                g_unsetenv                          (const gchar *variable);
gchar **            g_listenv                           (void);
const gchar *       g_get_user_name                     (void);
const gchar *       g_get_real_name                     (void);
const gchar *       g_get_user_cache_dir                (void);
const gchar *       g_get_user_data_dir                 (void);
const gchar *       g_get_user_config_dir               (void);
const gchar *       g_get_user_runtime_dir              (void);
enum                GUserDirectory;
const gchar *       g_get_user_special_dir              (GUserDirectory directory);
const gchar * const * g_get_system_data_dirs            (void);
const gchar * const * g_get_system_config_dirs          (void);
void                g_reload_user_special_dirs_cache    (void);

const gchar *       g_get_host_name                     (void);
const gchar *       g_get_home_dir                      (void);
const gchar *       g_get_tmp_dir                       (void);
gchar *             g_get_current_dir                   (void);
const gchar *       g_basename                          (const gchar *file_name);
#define             g_dirname
gboolean            g_path_is_absolute                  (const gchar *file_name);
const gchar *       g_path_skip_root                    (const gchar *file_name);
gchar *             g_path_get_basename                 (const gchar *file_name);
gchar *             g_path_get_dirname                  (const gchar *file_name);
gchar *             g_build_filename                    (const gchar *first_element,
                                                         ...);
gchar *             g_build_filenamev                   (gchar **args);
gchar *             g_build_path                        (const gchar *separator,
                                                         const gchar *first_element,
                                                         ...);
gchar *             g_build_pathv                       (const gchar *separator,
                                                         gchar **args);

gchar *             g_format_size                       (guint64 size);
enum                GFormatSizeFlags;
gchar *             g_format_size_full                  (guint64 size,
                                                         GFormatSizeFlags flags);
gchar *             g_format_size_for_display           (goffset size);

gchar *             g_find_program_in_path              (const gchar *program);

gint                g_bit_nth_lsf                       (gulong mask,
                                                         gint nth_bit);
gint                g_bit_nth_msf                       (gulong mask,
                                                         gint nth_bit);
guint               g_bit_storage                       (gulong number);

guint               g_spaced_primes_closest             (guint num);

void                g_atexit                            (GVoidFunc func);

guint               g_parse_debug_string                (const gchar *string,
                                                         const GDebugKey *keys,
                                                         guint nkeys);
struct              GDebugKey;

void                (*GVoidFunc)                        (void);
void                (*GFreeFunc)                        (gpointer data);

void                g_qsort_with_data                   (gconstpointer pbase,
                                                         gint total_elems,
                                                         gsize size,
                                                         GCompareDataFunc compare_func,
                                                         gpointer user_data);

void                g_nullify_pointer                   (gpointer *nullify_location);

Description

These are portable utility functions.

Details

g_get_application_name ()

const gchar *       g_get_application_name              (void);

Gets a human-readable name for the application, as set by g_set_application_name(). This name should be localized if possible, and is intended for display to the user. Contrast with g_get_prgname(), which gets a non-localized name. If g_set_application_name() has not been called, returns the result of g_get_prgname() (which may be NULL if g_set_prgname() has also not been called).

Returns :

human-readable application name. may return NULL

Since 2.2


g_set_application_name ()

void                g_set_application_name              (const gchar *application_name);

Sets a human-readable name for the application. This name should be localized if possible, and is intended for display to the user. Contrast with g_set_prgname(), which sets a non-localized name. g_set_prgname() will be called automatically by gtk_init(), but g_set_application_name() will not.

Note that for thread safety reasons, this function can only be called once.

The application name will be used in contexts such as error messages, or when displaying an application's name in the task list.

application_name :

localized name of the application

Since 2.2


g_get_prgname ()

gchar *             g_get_prgname                       (void);

Gets the name of the program. This name should not be localized, contrast with g_get_application_name(). (If you are using GDK or GTK+ the program name is set in gdk_init(), which is called by gtk_init(). The program name is found by taking the last component of argv[0].)

Returns :

the name of the program. The returned string belongs to GLib and must not be modified or freed.

g_set_prgname ()

void                g_set_prgname                       (const gchar *prgname);

Sets the name of the program. This name should not be localized, contrast with g_set_application_name(). Note that for thread-safety reasons this function can only be called once.

prgname :

the name of the program.

g_get_environ ()

gchar **            g_get_environ                       (void);

Gets the list of environment variables for the current process.

The list is NULL terminated and each item in the list is of the form 'NAME=VALUE'.

This is equivalent to direct access to the 'environ' global variable, except portable.

The return value is freshly allocated and it should be freed with g_strfreev() when it is no longer needed.

Returns :

the list of environment variables. [array zero-terminated=1][transfer full]

Since 2.28


g_environ_getenv ()

const gchar *       g_environ_getenv                    (gchar **envp,
                                                         const gchar *variable);

Returns the value of the environment variable variable in the provided list envp.

The name and value are in the GLib file name encoding. On UNIX, this means the actual bytes which might or might not be in some consistent character set and encoding. On Windows, it is in UTF-8. On Windows, in case the environment variable's value contains references to other environment variables, they are expanded.

envp :

an environment list (eg, as returned from g_get_environ()). [array zero-terminated=1][transfer none]

variable :

the environment variable to get, in the GLib file name encoding

Returns :

the value of the environment variable, or NULL if the environment variable is not set in envp. The returned string is owned by envp, and will be freed if variable is set or unset again.

Since 2.32


g_environ_setenv ()

gchar **            g_environ_setenv                    (gchar **envp,
                                                         const gchar *variable,
                                                         const gchar *value,
                                                         gboolean overwrite);

Sets the environment variable variable in the provided list envp to value.

Both the variable's name and value should be in the GLib file name encoding. On UNIX, this means that they can be arbitrary byte strings. On Windows, they should be in UTF-8.

envp :

an environment list that can be freed using g_strfreev() (e.g., as returned from g_get_environ()). [array zero-terminated=1][transfer full]

variable :

the environment variable to set, must not contain '='

value :

the value for to set the variable to

overwrite :

whether to change the variable if it already exists

Returns :

the updated environment list. Free it using g_strfreev(). [array zero-terminated=1][transfer full]

Since 2.32


g_environ_unsetenv ()

gchar **            g_environ_unsetenv                  (gchar **envp,
                                                         const gchar *variable);

Removes the environment variable variable from the provided environment envp.

envp :

an environment list that can be freed using g_strfreev() (e.g., as returned from g_get_environ()). [array zero-terminated=1][transfer full]

variable :

the environment variable to remove, must not contain '='

Returns :

the updated environment list. Free it using g_strfreev(). [array zero-terminated=1][transfer full]

Since 2.32


g_getenv ()

const gchar *       g_getenv                            (const gchar *variable);

Returns the value of an environment variable.

The name and value are in the GLib file name encoding. On UNIX, this means the actual bytes which might or might not be in some consistent character set and encoding. On Windows, it is in UTF-8. On Windows, in case the environment variable's value contains references to other environment variables, they are expanded.

variable :

the environment variable to get, in the GLib file name encoding

Returns :

the value of the environment variable, or NULL if the environment variable is not found. The returned string may be overwritten by the next call to g_getenv(), g_setenv() or g_unsetenv().

g_setenv ()

gboolean            g_setenv                            (const gchar *variable,
                                                         const gchar *value,
                                                         gboolean overwrite);

Sets an environment variable. Both the variable's name and value should be in the GLib file name encoding. On UNIX, this means that they can be arbitrary byte strings. On Windows, they should be in UTF-8.

Note that on some systems, when variables are overwritten, the memory used for the previous variables and its value isn't reclaimed.

Warning

Environment variable handling in UNIX is not thread-safe, and your program may crash if one thread calls g_setenv() while another thread is calling getenv(). (And note that many functions, such as gettext(), call getenv() internally.) This function is only safe to use at the very start of your program, before creating any other threads (or creating objects that create worker threads of their own).

If you need to set up the environment for a child process, you can use g_get_environ() to get an environment array, modify that with g_environ_setenv() and g_environ_unsetenv(), and then pass that array directly to execvpe(), g_spawn_async(), or the like.

variable :

the environment variable to set, must not contain '='.

value :

the value for to set the variable to.

overwrite :

whether to change the variable if it already exists.

Returns :

FALSE if the environment variable couldn't be set.

Since 2.4


g_unsetenv ()

void                g_unsetenv                          (const gchar *variable);

Removes an environment variable from the environment.

Note that on some systems, when variables are overwritten, the memory used for the previous variables and its value isn't reclaimed.

Warning

Environment variable handling in UNIX is not thread-safe, and your program may crash if one thread calls g_unsetenv() while another thread is calling getenv(). (And note that many functions, such as gettext(), call getenv() internally.) This function is only safe to use at the very start of your program, before creating any other threads (or creating objects that create worker threads of their own).

If you need to set up the environment for a child process, you can use g_get_environ() to get an environment array, modify that with g_environ_setenv() and g_environ_unsetenv(), and then pass that array directly to execvpe(), g_spawn_async(), or the like.

variable :

the environment variable to remove, must not contain '='

Since 2.4


g_listenv ()

gchar **            g_listenv                           (void);

Gets the names of all variables set in the environment.

Programs that want to be portable to Windows should typically use this function and g_getenv() instead of using the environ array from the C library directly. On Windows, the strings in the environ array are in system codepage encoding, while in most of the typical use cases for environment variables in GLib-using programs you want the UTF-8 encoding that this function and g_getenv() provide.

Returns :

a NULL-terminated list of strings which must be freed with g_strfreev(). [array zero-terminated=1][transfer full]

Since 2.8


g_get_user_name ()

const gchar *       g_get_user_name                     (void);

Gets the user name of the current user. The encoding of the returned string is system-defined. On UNIX, it might be the preferred file name encoding, or something else, and there is no guarantee that it is even consistent on a machine. On Windows, it is always UTF-8.

Returns :

the user name of the current user.

g_get_real_name ()

const gchar *       g_get_real_name                     (void);

Gets the real name of the user. This usually comes from the user's entry in the passwd file. The encoding of the returned string is system-defined. (On Windows, it is, however, always UTF-8.) If the real user name cannot be determined, the string "Unknown" is returned.

Returns :

the user's real name.

g_get_user_cache_dir ()

const gchar *       g_get_user_cache_dir                (void);

Returns a base directory in which to store non-essential, cached data specific to particular user.

On UNIX platforms this is determined using the mechanisms described in the XDG Base Directory Specification. In this case the directory retrieved will be XDG_CACHE_HOME.

On Windows is the directory that serves as a common repository for temporary Internet files. A typical path is C:\Documents and Settings\username\Local Settings\Temporary Internet Files. See documentation for CSIDL_INTERNET_CACHE.

Returns :

a string owned by GLib that must not be modified or freed.

Since 2.6


g_get_user_data_dir ()

const gchar *       g_get_user_data_dir                 (void);

Returns a base directory in which to access application data such as icons that is customized for a particular user.

On UNIX platforms this is determined using the mechanisms described in the XDG Base Directory Specification. In this case the directory retrieved will be XDG_DATA_HOME.

On Windows this is the folder to use for local (as opposed to roaming) application data. See documentation for CSIDL_LOCAL_APPDATA. Note that on Windows it thus is the same as what g_get_user_config_dir() returns.

Returns :

a string owned by GLib that must not be modified or freed.

Since 2.6


g_get_user_config_dir ()

const gchar *       g_get_user_config_dir               (void);

Returns a base directory in which to store user-specific application configuration information such as user preferences and settings.

On UNIX platforms this is determined using the mechanisms described in the XDG Base Directory Specification. In this case the directory retrieved will be XDG_CONFIG_HOME.

On Windows this is the folder to use for local (as opposed to roaming) application data. See documentation for CSIDL_LOCAL_APPDATA. Note that on Windows it thus is the same as what g_get_user_data_dir() returns.

Returns :

a string owned by GLib that must not be modified or freed.

Since 2.6


g_get_user_runtime_dir ()

const gchar *       g_get_user_runtime_dir              (void);

Returns a directory that is unique to the current user on the local system.

On UNIX platforms this is determined using the mechanisms described in the XDG Base Directory Specification. This is the directory specified in the XDG_RUNTIME_DIR environment variable. In the case that this variable is not set, GLib will issue a warning message to stderr and return the value of g_get_user_cache_dir().

On Windows this is the folder to use for local (as opposed to roaming) application data. See documentation for CSIDL_LOCAL_APPDATA. Note that on Windows it thus is the same as what g_get_user_config_dir() returns.

Returns :

a string owned by GLib that must not be modified or freed.

Since 2.28


enum GUserDirectory

typedef enum {
  G_USER_DIRECTORY_DESKTOP,
  G_USER_DIRECTORY_DOCUMENTS,
  G_USER_DIRECTORY_DOWNLOAD,
  G_USER_DIRECTORY_MUSIC,
  G_USER_DIRECTORY_PICTURES,
  G_USER_DIRECTORY_PUBLIC_SHARE,
  G_USER_DIRECTORY_TEMPLATES,
  G_USER_DIRECTORY_VIDEOS,

  G_USER_N_DIRECTORIES
} GUserDirectory;

These are logical ids for special directories which are defined depending on the platform used. You should use g_get_user_special_dir() to retrieve the full path associated to the logical id.

The GUserDirectory enumeration can be extended at later date. Not every platform has a directory for every logical id in this enumeration.

G_USER_DIRECTORY_DESKTOP

the user's Desktop directory

G_USER_DIRECTORY_DOCUMENTS

the user's Documents directory

G_USER_DIRECTORY_DOWNLOAD

the user's Downloads directory

G_USER_DIRECTORY_MUSIC

the user's Music directory

G_USER_DIRECTORY_PICTURES

the user's Pictures directory

G_USER_DIRECTORY_PUBLIC_SHARE

the user's shared directory

G_USER_DIRECTORY_TEMPLATES

the user's Templates directory

G_USER_DIRECTORY_VIDEOS

the user's Movies directory

G_USER_N_DIRECTORIES

the number of enum values

Since 2.14


g_get_user_special_dir ()

const gchar *       g_get_user_special_dir              (GUserDirectory directory);

Returns the full path of a special directory using its logical id.

On Unix this is done using the XDG special user directories. For compatibility with existing practise, G_USER_DIRECTORY_DESKTOP falls back to $HOME/Desktop when XDG special user directories have not been set up.

Depending on the platform, the user might be able to change the path of the special directory without requiring the session to restart; GLib will not reflect any change once the special directories are loaded.

directory :

the logical id of special directory

Returns :

the path to the specified special directory, or NULL if the logical id was not found. The returned string is owned by GLib and should not be modified or freed.

Since 2.14


g_get_system_data_dirs ()

const gchar * const * g_get_system_data_dirs            (void);

Returns an ordered list of base directories in which to access system-wide application data.

On UNIX platforms this is determined using the mechanisms described in the XDG Base Directory Specification In this case the list of directories retrieved will be XDG_DATA_DIRS.

On Windows the first elements in the list are the Application Data and Documents folders for All Users. (These can be determined only on Windows 2000 or later and are not present in the list on other Windows versions.) See documentation for CSIDL_COMMON_APPDATA and CSIDL_COMMON_DOCUMENTS.

Then follows the "share" subfolder in the installation folder for the package containing the DLL that calls this function, if it can be determined.

Finally the list contains the "share" subfolder in the installation folder for GLib, and in the installation folder for the package the application's .exe file belongs to.

The installation folders above are determined by looking up the folder where the module (DLL or EXE) in question is located. If the folder's name is "bin", its parent is used, otherwise the folder itself.

Note that on Windows the returned list can vary depending on where this function is called.

Returns :

a NULL-terminated array of strings owned by GLib that must not be modified or freed. [array zero-terminated=1][transfer none]

Since 2.6


g_get_system_config_dirs ()

const gchar * const * g_get_system_config_dirs          (void);

Returns an ordered list of base directories in which to access system-wide configuration information.

On UNIX platforms this is determined using the mechanisms described in the XDG Base Directory Specification. In this case the list of directories retrieved will be XDG_CONFIG_DIRS.

On Windows is the directory that contains application data for all users. A typical path is C:\Documents and Settings\All Users\Application Data. This folder is used for application data that is not user specific. For example, an application can store a spell-check dictionary, a database of clip art, or a log file in the CSIDL_COMMON_APPDATA folder. This information will not roam and is available to anyone using the computer.

Returns :

a NULL-terminated array of strings owned by GLib that must not be modified or freed. [array zero-terminated=1][transfer none]

Since 2.6


g_reload_user_special_dirs_cache ()

void                g_reload_user_special_dirs_cache    (void);

Resets the cache used for g_get_user_special_dir(), so that the latest on-disk version is used. Call this only if you just changed the data on disk yourself.

Due to threadsafety issues this may cause leaking of strings that were previously returned from g_get_user_special_dir() that can't be freed. We ensure to only leak the data for the directories that actually changed value though.

Since 2.22


g_get_host_name ()

const gchar *       g_get_host_name                     (void);

Return a name for the machine.

The returned name is not necessarily a fully-qualified domain name, or even present in DNS or some other name service at all. It need not even be unique on your local network or site, but usually it is. Callers should not rely on the return value having any specific properties like uniqueness for security purposes. Even if the name of the machine is changed while an application is running, the return value from this function does not change. The returned string is owned by GLib and should not be modified or freed. If no name can be determined, a default fixed string "localhost" is returned.

Returns :

the host name of the machine.

Since 2.8


g_get_home_dir ()

const gchar *       g_get_home_dir                      (void);

Gets the current user's home directory as defined in the password database.

Note that in contrast to traditional UNIX tools, this function prefers passwd entries over the HOME environment variable.

One of the reasons for this decision is that applications in many cases need special handling to deal with the case where HOME is

Not owned by the user
Not writeable
Not even readable

Since applications are in general not written to deal with these situations it was considered better to make g_get_home_dir() not pay attention to HOME and to return the real home directory for the user. If applications want to pay attention to HOME, they can do:

1
2
3
const char *homedir = g_getenv ("HOME");
 if (!homedir)
    homedir = g_get_home_dir ();

Returns :

the current user's home directory

g_get_tmp_dir ()

const gchar *       g_get_tmp_dir                       (void);

Gets the directory to use for temporary files. This is found from inspecting the environment variables TMPDIR, TMP, and TEMP in that order. If none of those are defined "/tmp" is returned on UNIX and "C:\" on Windows. The encoding of the returned string is system-defined. On Windows, it is always UTF-8. The return value is never NULL or the empty string.

Returns :

the directory to use for temporary files.

g_get_current_dir ()

gchar *             g_get_current_dir                   (void);

Gets the current directory.

The returned string should be freed when no longer needed. The encoding of the returned string is system defined. On Windows, it is always UTF-8.

Returns :

the current directory

g_basename ()

const gchar *       g_basename                          (const gchar *file_name);

Warning

g_basename has been deprecated since version 2.2 and should not be used in newly-written code. Use g_path_get_basename() instead, but notice that g_path_get_basename() allocates new memory for the returned string, unlike this function which returns a pointer into the argument.

Gets the name of the file without any leading directory components. It returns a pointer into the given file name string.

file_name :

the name of the file

Returns :

the name of the file without any leading directory components

g_dirname

#define             g_dirname

Warning

g_dirname is deprecated and should not be used in newly-written code. use g_path_get_dirname() instead

Gets the directory components of a file name.

If the file name has no directory components "." is returned. The returned string should be freed when no longer needed.

file_name :

the name of the file

Returns :

the directory components of the file

g_path_is_absolute ()

gboolean            g_path_is_absolute                  (const gchar *file_name);

Returns TRUE if the given file_name is an absolute file name. Note that this is a somewhat vague concept on Windows.

On POSIX systems, an absolute file name is well-defined. It always starts from the single root directory. For example "/usr/local".

On Windows, the concepts of current drive and drive-specific current directory introduce vagueness. This function interprets as an absolute file name one that either begins with a directory separator such as "\Users\tml" or begins with the root on a drive, for example "C:\Windows". The first case also includes UNC paths such as "\\myserver\docs\foo". In all cases, either slashes or backslashes are accepted.

Note that a file name relative to the current drive root does not truly specify a file uniquely over time and across processes, as the current drive is a per-process value and can be changed.

File names relative the current directory on some specific drive, such as "D:foo/bar", are not interpreted as absolute by this function, but they obviously are not relative to the normal current directory as returned by getcwd() or g_get_current_dir() either. Such paths should be avoided, or need to be handled using Windows-specific code.

file_name :

a file name

Returns :

TRUE if file_name is absolute

g_path_skip_root ()

const gchar *       g_path_skip_root                    (const gchar *file_name);

Returns a pointer into file_name after the root component, i.e. after the "/" in UNIX or "C:\" under Windows. If file_name is not an absolute path it returns NULL.

file_name :

a file name

Returns :

a pointer into file_name after the root component

g_path_get_basename ()

gchar *             g_path_get_basename                 (const gchar *file_name);

Gets the last component of the filename.

If file_name ends with a directory separator it gets the component before the last slash. If file_name consists only of directory separators (and on Windows, possibly a drive letter), a single separator is returned. If file_name is empty, it gets ".".

file_name :

the name of the file

Returns :

a newly allocated string containing the last component of the filename

g_path_get_dirname ()

gchar *             g_path_get_dirname                  (const gchar *file_name);

Gets the directory components of a file name.

If the file name has no directory components "." is returned. The returned string should be freed when no longer needed.

file_name :

the name of the file

Returns :

the directory components of the file

g_build_filename ()

gchar *             g_build_filename                    (const gchar *first_element,
                                                         ...);

Creates a filename from a series of elements using the correct separator for filenames.

On Unix, this function behaves identically to g_build_path (G_DIR_SEPARATOR_S, first_element, ....).

On Windows, it takes into account that either the backslash (\ or slash (/) can be used as separator in filenames, but otherwise behaves as on Unix. When file pathname separators need to be inserted, the one that last previously occurred in the parameters (reading from left to right) is used.

No attempt is made to force the resulting filename to be an absolute path. If the first element is a relative path, the result will be a relative path.

first_element :

the first element in the path

... :

remaining elements in path, terminated by NULL

Returns :

a newly-allocated string that must be freed with g_free().

g_build_filenamev ()

gchar *             g_build_filenamev                   (gchar **args);

Behaves exactly like g_build_filename(), but takes the path elements as a string array, instead of varargs. This function is mainly meant for language bindings.

args :

NULL-terminated array of strings containing the path elements. [array zero-terminated=1]

Returns :

a newly-allocated string that must be freed with g_free().

Since 2.8


g_build_path ()

gchar *             g_build_path                        (const gchar *separator,
                                                         const gchar *first_element,
                                                         ...);

Creates a path from a series of elements using separator as the separator between elements. At the boundary between two elements, any trailing occurrences of separator in the first element, or leading occurrences of separator in the second element are removed and exactly one copy of the separator is inserted.

Empty elements are ignored.

The number of leading copies of the separator on the result is the same as the number of leading copies of the separator on the first non-empty element.

The number of trailing copies of the separator on the result is the same as the number of trailing copies of the separator on the last non-empty element. (Determination of the number of trailing copies is done without stripping leading copies, so if the separator is ABA, ABABA has 1 trailing copy.)

However, if there is only a single non-empty element, and there are no characters in that element not part of the leading or trailing separators, then the result is exactly the original value of that element.

Other than for determination of the number of leading and trailing copies of the separator, elements consisting only of copies of the separator are ignored.

separator :

a string used to separator the elements of the path.

first_element :

the first element in the path

... :

remaining elements in path, terminated by NULL

Returns :

a newly-allocated string that must be freed with g_free().

g_build_pathv ()

gchar *             g_build_pathv                       (const gchar *separator,
                                                         gchar **args);

Behaves exactly like g_build_path(), but takes the path elements as a string array, instead of varargs. This function is mainly meant for language bindings.

separator :

a string used to separator the elements of the path.

args :

NULL-terminated array of strings containing the path elements. [array zero-terminated=1]

Returns :

a newly-allocated string that must be freed with g_free().

Since 2.8


g_format_size ()

gchar *             g_format_size                       (guint64 size);

Formats a size (for example the size of a file) into a human readable string. Sizes are rounded to the nearest size prefix (kB, MB, GB) and are displayed rounded to the nearest tenth. E.g. the file size 3292528 bytes will be converted into the string "3.2 MB".

The prefix units base is 1000 (i.e. 1 kB is 1000 bytes).

This string should be freed with g_free() when not needed any longer.

See g_format_size_full() for more options about how the size might be formatted.

size :

a size in bytes

Returns :

a newly-allocated formatted string containing a human readable file size

Since 2.30


enum GFormatSizeFlags

typedef enum {
  G_FORMAT_SIZE_DEFAULT     = 0,
  G_FORMAT_SIZE_LONG_FORMAT = 1 << 0,
  G_FORMAT_SIZE_IEC_UNITS   = 1 << 1
} GFormatSizeFlags;

Flags to modify the format of the string returned by g_format_size_full().

G_FORMAT_SIZE_DEFAULT

behave the same as g_format_size()

G_FORMAT_SIZE_LONG_FORMAT

include the exact number of bytes as part of the returned string. For example, "45.6 kB (45,612 bytes)".

G_FORMAT_SIZE_IEC_UNITS

use IEC (base 1024) units with "KiB"-style suffixes. IEC units should only be used for reporting things with a strong "power of 2" basis, like RAM sizes or RAID stripe sizes. Network and storage sizes should be reported in the normal SI units.

g_format_size_full ()

gchar *             g_format_size_full                  (guint64 size,
                                                         GFormatSizeFlags flags);

Formats a size.

This function is similar to g_format_size() but allows for flags that modify the output. See GFormatSizeFlags.

size :

a size in bytes

flags :

GFormatSizeFlags to modify the output

Returns :

a newly-allocated formatted string containing a human readable file size

Since 2.30


g_format_size_for_display ()

gchar *             g_format_size_for_display           (goffset size);

Warning

g_format_size_for_display has been deprecated since version 2.30 and should not be used in newly-written code. This function is broken due to its use of SI suffixes to denote IEC units. Use g_format_size() instead.

Formats a size (for example the size of a file) into a human readable string. Sizes are rounded to the nearest size prefix (KB, MB, GB) and are displayed rounded to the nearest tenth. E.g. the file size 3292528 bytes will be converted into the string "3.1 MB".

The prefix units base is 1024 (i.e. 1 KB is 1024 bytes).

This string should be freed with g_free() when not needed any longer.

size :

a size in bytes

Returns :

a newly-allocated formatted string containing a human readable file size

Since 2.16


g_find_program_in_path ()

gchar *             g_find_program_in_path              (const gchar *program);

Locates the first executable named program in the user's path, in the same way that execvp() would locate it. Returns an allocated string with the absolute path name, or NULL if the program is not found in the path. If program is already an absolute path, returns a copy of program if program exists and is executable, and NULL otherwise. On Windows, if program does not have a file type suffix, tries with the suffixes .exe, .cmd, .bat and .com, and the suffixes in the PATHEXT environment variable.

On Windows, it looks for the file in the same way as CreateProcess() would. This means first in the directory where the executing program was loaded from, then in the current directory, then in the Windows 32-bit system directory, then in the Windows directory, and finally in the directories in the PATH environment variable. If the program is found, the return value contains the full name including the type suffix.

program :

a program name in the GLib file name encoding

Returns :

absolute path, or NULL

g_bit_nth_lsf ()

gint                g_bit_nth_lsf                       (gulong mask,
                                                         gint nth_bit);

Find the position of the first bit set in mask, searching from (but not including) nth_bit upwards. Bits are numbered from 0 (least significant) to sizeof(gulong) * 8 - 1 (31 or 63, usually). To start searching from the 0th bit, set nth_bit to -1.

mask :

a gulong containing flags

nth_bit :

the index of the bit to start the search from

Returns :

the index of the first bit set which is higher than nth_bit

g_bit_nth_msf ()

gint                g_bit_nth_msf                       (gulong mask,
                                                         gint nth_bit);

Find the position of the first bit set in mask, searching from (but not including) nth_bit downwards. Bits are numbered from 0 (least significant) to sizeof(gulong) * 8 - 1 (31 or 63, usually). To start searching from the last bit, set nth_bit to -1 or GLIB_SIZEOF_LONG * 8.

mask :

a gulong containing flags

nth_bit :

the index of the bit to start the search from

Returns :

the index of the first bit set which is lower than nth_bit

g_bit_storage ()

guint               g_bit_storage                       (gulong number);

Gets the number of bits used to hold number, e.g. if number is 4, 3 bits are needed.

number :

a guint

Returns :

the number of bits used to hold number

g_spaced_primes_closest ()

guint               g_spaced_primes_closest             (guint num);

Gets the smallest prime number from a built-in array of primes which is larger than num. This is used within GLib to calculate the optimum size of a GHashTable.

The built-in array of primes ranges from 11 to 13845163 such that each prime is approximately 1.5-2 times the previous prime.

num :

a guint

Returns :

the smallest prime number from a built-in array of primes which is larger than num

g_atexit ()

void                g_atexit                            (GVoidFunc func);

Warning

g_atexit has been deprecated since version 2.32 and should not be used in newly-written code. It is best to avoid g_atexit().

Specifies a function to be called at normal program termination.

Since GLib 2.8.2, on Windows g_atexit() actually is a preprocessor macro that maps to a call to the atexit() function in the C library. This means that in case the code that calls g_atexit(), i.e. atexit(), is in a DLL, the function will be called when the DLL is detached from the program. This typically makes more sense than that the function is called when the GLib DLL is detached, which happened earlier when g_atexit() was a function in the GLib DLL.

The behaviour of atexit() in the context of dynamically loaded modules is not formally specified and varies wildly.

On POSIX systems, calling g_atexit() (or atexit()) in a dynamically loaded module which is unloaded before the program terminates might well cause a crash at program exit.

Some POSIX systems implement atexit() like Windows, and have each dynamically loaded module maintain an own atexit chain that is called when the module is unloaded.

On other POSIX systems, before a dynamically loaded module is unloaded, the registered atexit functions (if any) residing in that module are called, regardless where the code that registered them resided. This is presumably the most robust approach.

As can be seen from the above, for portability it's best to avoid calling g_atexit() (or atexit()) except in the main executable of a program.

func :

the function to call on normal program termination. [scope async]

g_parse_debug_string ()

guint               g_parse_debug_string                (const gchar *string,
                                                         const GDebugKey *keys,
                                                         guint nkeys);

Parses a string containing debugging options into a guint containing bit flags. This is used within GDK and GTK+ to parse the debug options passed on the command line or through environment variables.

If string is equal to "all", all flags are set. Any flags specified along with "all" in string are inverted; thus, "all,foo,bar" or "foo,bar,all" sets all flags except those corresponding to "foo" and "bar".

If string is equal to "help", all the available keys in keys are printed out to standard error.

string :

a list of debug options separated by colons, spaces, or commas, or NULL. [allow-none]

keys :

pointer to an array of GDebugKey which associate strings with bit flags. [array length=nkeys]

nkeys :

the number of GDebugKeys in the array.

Returns :

the combined set of bit flags.

struct GDebugKey

struct GDebugKey {
  const gchar *key;
  guint	       value;
};

Associates a string with a bit flag. Used in g_parse_debug_string().

const gchar *key;

the string

guint value;

the flag

GVoidFunc ()

void                (*GVoidFunc)                        (void);

Warning

GVoidFunc is deprecated and should not be used in newly-written code.

Declares a type of function which takes no arguments and has no return value. It is used to specify the type function passed to g_atexit().


GFreeFunc ()

void                (*GFreeFunc)                        (gpointer data);

Declares a type of function which takes an arbitrary data pointer argument and has no return value. It is not currently used in GLib or GTK+.

data :

a data pointer

g_qsort_with_data ()

void                g_qsort_with_data                   (gconstpointer pbase,
                                                         gint total_elems,
                                                         gsize size,
                                                         GCompareDataFunc compare_func,
                                                         gpointer user_data);

This is just like the standard C qsort() function, but the comparison routine accepts a user data argument.

This is guaranteed to be a stable sort since version 2.32.

pbase :

start of array to sort

total_elems :

elements in the array

size :

size of each element

compare_func :

function to compare elements

user_data :

data to pass to compare_func

g_nullify_pointer ()

void                g_nullify_pointer                   (gpointer *nullify_location);

Set the pointer at the specified location to NULL.

nullify_location :

the memory address of the pointer.