## Miscellaneous Utility Functions

Miscellaneous Utility Functions — a selection of portable utility functions.

## Synopsis

    #include <glib.h>

    G_CONST_RETURN 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);
    G_CONST_RETURN gchar* g_getenv              (const gchar *variable);
    gboolean    g_setenv                        (const gchar *variable,
                                                 const gchar *value,
                                                 gboolean overwrite);
    void        g_unsetenv                      (const gchar *variable);
    G_CONST_RETURN gchar* g_get_user_name       (void);
    G_CONST_RETURN gchar* g_get_real_name       (void);
    G_CONST_RETURN gchar* g_get_user_cache_dir  (void);
    G_CONST_RETURN gchar* g_get_user_data_dir   (void);
    G_CONST_RETURN gchar* g_get_user_config_dir (void);

    G_CONST_RETURN gchar* g_get_home_dir        (void);
    G_CONST_RETURN gchar* g_get_tmp_dir         (void);
    gchar*      g_get_current_dir               (void);
    G_CONST_RETURN gchar* g_basename            (const gchar *file_name);
    #define     g_dirname
    gboolean    g_path_is_absolute              (const gchar *file_name);
    G_CONST_RETURN 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_path                    (const gchar *separator,
                                                 const gchar *first_element,
                                                 ...);

    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 ()

    G_CONST_RETURN 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

### 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_getenv ()

    G_CONST_RETURN 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 any sequence of bytes. 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.

`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. Furthermore, this function can't be guaranteed to operate in a threadsafe way.

`variable` : | the environment variable to remove, must not contain '='.

Since 2.4

### g_get_user_name ()

    G_CONST_RETURN 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 ()

    G_CONST_RETURN 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 ()

    G_CONST_RETURN 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

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

Since 2.6

### g_get_user_data_dir ()

    G_CONST_RETURN 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

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

Since 2.6

### g_get_user_config_dir ()

    G_CONST_RETURN 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

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

Since 2.6

### g_get_home_dir ()

    G_CONST_RETURN gchar* g_get_home_dir        (void);

Gets the current user's home directory.

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

Returns : | the current user's home directory.

### g_get_tmp_dir ()

    G_CONST_RETURN 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.

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 ()

    G_CONST_RETURN gchar* g_basename            (const gchar *file_name);

### Warning

`g_basename` is deprecated 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.

This function is deprecated and will be removed in the next major release of GLib. 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.

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, i.e. it contains a full path from the root directory such as '/usr/local' on UNIX or 'C:\windows' on Windows systems.

`file_name` : | a file name.
Returns : | `TRUE` if `file_name` is an absolute path.

### g_path_skip_root ()

    G_CONST_RETURN 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_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_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.

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);

Specifies a function to be called at normal program termination.

`func` : | the function to call on normal program termination.

### g_parse_debug_string ()

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

Parses a string containing debugging options separated by ':' 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.

`string` : | a list of debug options separated by ':' or "all" to set all flags.
`keys` : | pointer to an array of GDebugKey which associate strings with bit flags.
`nkeys` : | the number of GDebugKey in the array.
Returns : | the combined set of bit flags.

### struct GDebugKey

    struct GDebugKey {

      gchar *key;
      guint	 value;
    };

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

### GVoidFunc ()

    void        (*GVoidFunc)                    (void);

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.

`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.