Name

enum GFileError

typedef enum
{
  G_FILE_ERROR_EXIST, G_FILE_ERROR_ISDIR, G_FILE_ERROR_ACCES, G_FILE_ERROR_NAMETOOLONG, G_FILE_ERROR_NOENT, G_FILE_ERROR_NOTDIR,
  G_FILE_ERROR_NXIO, G_FILE_ERROR_NODEV, G_FILE_ERROR_ROFS, G_FILE_ERROR_TXTBSY, G_FILE_ERROR_FAULT, G_FILE_ERROR_LOOP, G_FILE_ERROR_NOSPC,
  G_FILE_ERROR_NOMEM, G_FILE_ERROR_MFILE, G_FILE_ERROR_NFILE, G_FILE_ERROR_BADF, G_FILE_ERROR_INVAL, G_FILE_ERROR_PIPE, G_FILE_ERROR_AGAIN,
  G_FILE_ERROR_INTR, G_FILE_ERROR_IO, G_FILE_ERROR_PERM, G_FILE_ERROR_NOSYS, G_FILE_ERROR_FAILED
} GFileError;

Values corresponding to errno codes returned from file operations on UNIX. Unlike errno codes, GFileError values are available on all systems, even Windows. The exact meaning of each code depends on what sort of file operation was performed; the UNIX documentation gives more details. The following error code descriptions come from the GNU C Library manual, and are under the copyright of that manual.

It's not very portable to make detailed assumptions about exactly which errors will be returned from a given operation. Some errors don't occur on some systems, etc., sometimes there are subtle differences in when a system will report a given error, etc.

G_FILE_ERROR

#define G_FILE_ERROR g_file_error_quark ()

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

enum GFileTest

typedef enum
{
  G_FILE_TEST_IS_REGULAR    = 1 << 0,
  G_FILE_TEST_IS_SYMLINK    = 1 << 1,
  G_FILE_TEST_IS_DIR        = 1 << 2,
  G_FILE_TEST_IS_EXECUTABLE = 1 << 3,
  G_FILE_TEST_EXISTS        = 1 << 4
} GFileTest;

A test to perform on a file using g_file_test().

g_file_error_from_errno ()

GFileError  g_file_error_from_errno         (gint err_no);

Gets a GFileError constant based on the passed-in errno. For example, if EEXIST is passed-in this function returns G_FILE_ERROR_EXIST. Unlike errno values, portably assume that all GFileError values will exist.

Normally a GFileError value goes into a GError returned from a function that manipulates files. Use g_file_error_from_errno() when constructing a GError.

g_file_get_contents ()

gboolean    g_file_get_contents             (const gchar *filename, gchar **contents, gsize *length, GError **error);

Reads an entire file into allocated memory, with good error checking.

If the call was successful, it returns TRUE and sets contents to the file contents and length to the length of the file contents in bytes. The string stored in contents will be null-terminated, so for text files pass NULL for the length argument. If the call was not successful, it returns FALSE and sets error. The error domain is G_FILE_ERROR. Possible error codes are those in the GFileError enumeration. In the error case, contents is set to NULL and length is set to zero.

g_file_set_contents ()

gboolean    g_file_set_contents        (const gchar *filename, const gchar *contents, gssize length, GError **error);

Writes all of contents to a file named filename, with good error checking. If a file called filename already exists it will be overwritten.

This write is atomic in the sense that it is first written to a temporary file which is then renamed to the final name. Notes:

If the call was successful, it returns TRUE. If the call was not successful, it returns FALSE and sets error. The error domain is G_FILE_ERROR. Possible error codes are those in the GFileError enumeration.

g_file_test ()

gboolean    g_file_test         (const gchar *filename, GFileTest test);

Returns TRUE if any of the tests in the bitfield test are TRUE. For example, (G_FILE_TEST_EXISTS | G_FILE_TEST_IS_DIR) will return TRUE if the file exists; the check whether it is a directory does not matter since the existence test is TRUE. With the current set of available tests, there is no point passing in more than one test at a time.

Apart from G_FILE_TEST_IS_SYMLINK all tests follow symbolic links, so for a symbolic link to a regular file g_file_test() will return TRUE for both G_FILE_TEST_IS_SYMLINK and G_FILE_TEST_IS_REGULAR.

Note, that for a dangling symbolic link g_file_test() will return TRUE for G_FILE_TEST_IS_SYMLINK and FALSE for all other flags.

Never use g_file_test() to test whether it is safe to perform an operation, because there is always the possibility of the condition changing before the actual operation is perfromed. For example,the use of G_FILE_TEST_IS_SYMLINK to know whether it is is safe to write to a file without being tricked into writing into a different location. It does not work.

/* DON'T DO THIS */
 if (!g_file_test (filename, G_FILE_TEST_IS_SYMLINK)) {
   fd = g_open (filename, O_WRONLY);
   /* write to fd */
 }

Another thing to note is that G_FILE_TEST_EXISTS and G_FILE_TEST_IS_EXECUTABLE are implemented using the access() system call. This usually does not matter, but if the program is setuid or setgid it means that these tests will give the answer for the real user ID and group ID, rather than the effective user ID and group ID.

On Windows, there are no symlinks, so testing for G_FILE_TEST_IS_SYMLINK will always return FALSE. Testing for G_FILE_TEST_IS_EXECUTABLE will just check that the file exists and its name indicates that it is executable, checking for well-known extensions and those listed in the PATHEXT environment variable.

g_mkstemp ()

gint        g_mkstemp            (gchar *tmpl);

Opens a temporary file. See the mkstemp() documentation on most UNIX-like systems. This is a portability wrapper, which simply calls mkstemp() on systems that have it, and implements it in GLib otherwise.

The parameter is a string that should match the rules for mkstemp(), i.e. end in "XXXXXX". The X string will be modified to form the name of a file that did not exist. The string should be in the GLib file name encoding. Most importantly, on Windows it should be in UTF-8.

g_file_open_tmp ()

gint        g_file_open_tmp             (const gchar *tmpl, gchar **name_used, GError **error);

Opens a file for writing in the preferred directory for temporary files (as returned by g_get_tmp_dir()).

tmpl should be a string in the GLib file name encoding ending with six 'X' characters, as the parameter to g_mkstemp() (or mkstemp()). However, unlike these functions, the template should only be a basename, no directory components are allowed. If template is NULL, a default template is used.

Note that in contrast to g_mkstemp() (and mkstemp()) tmpl is not modified, and might thus be a read-only literal string.

The actual name used is returned in name_used if non-NULL. This string should be freed with g_free() when not needed any longer. The returned name is in the GLib file name encoding.

g_file_read_link ()

gchar*      g_file_read_link                (const gchar *filename, GError **error);

Reads the contents of the symbolic link filename like the POSIX readlink() function. The returned string is in the encoding used for filenames. Use g_filename_to_utf8() to convert it to UTF-8.

g_mkdir_with_parents ()

int         g_mkdir_with_parents            (const gchar *pathname, int mode);

Create a directory if it does not already exist. Create intermediate parent directories as needed, too.

GDir

typedef struct _GDir GDir;

An opaque structure representing an opened directory.

g_dir_open ()

GDir*       g_dir_open            (const gchar *path, guint flags, GError **error);

Opens a directory for reading. The names of the files in the directory can then be retrieved using g_dir_read_name().

g_dir_read_name ()

const gchar* g_dir_read_name         (GDir *dir);

Retrieves the name of the next entry in the directory. The '.' and '..' entries are omitted. On Windows, the returned name is in UTF-8. On Unix, it is in the on-disk encoding.

g_dir_rewind ()

void        g_dir_rewind                    (GDir *dir);

Resets the given directory. The next call to g_dir_read_name() will return the first entry again.

g_dir_close ()

void        g_dir_close                     (GDir *dir);

Closes the directory and deallocates all related resources.

GMappedFile

typedef struct _GMappedFile GMappedFile;

The GMappedFile represents a file mapping created with g_mapped_file_new(). It has only private members and should not be accessed directly.

g_mapped_file_new ()

GMappedFile* g_mapped_file_new              (const gchar *filename, gboolean writable, GError **error);

Maps a file into memory. On UNIX, this is using the mmap() function.

If writable is TRUE, the mapped buffer may be modified, otherwise it is an error to modify the mapped buffer. Modifications to the buffer are not visible to other processes mapping the same file, and are not written back to the file.

Note that modifications of the underlying file might affect the contents of the GMappedFile. Therefore, mapping should only be used if the file will not be modified, or if all modifications of the file are done atomically (e.g. using g_file_set_contents()).

g_mapped_file_free ()

void        g_mapped_file_free              (GMappedFile *file);

Unmaps the buffer of file and frees it.

g_mapped_file_get_length ()

gsize       g_mapped_file_get_length        (GMappedFile *file);

Returns the length of the contents of a GMappedFile.

g_mapped_file_get_contents ()

gchar*      g_mapped_file_get_contents      (GMappedFile *file);

Returns the contents of a GMappedFile.

Note that the contents may not be zero-terminated, even if the GMappedFile is backed by a text file.

g_open ()

int         g_open            (const gchar *filename, int flags, int mode);

A wrapper for the POSIX open() function. The open() function is used to convert a pathname into a file descriptor. Note that on POSIX systems file descriptors are implemented by the operating system. On Windows, it is the C library that implements open() and file descriptors. The actual Windows API for opening files is something different.

See the C library manual for more details about open().

g_rename ()

int         g_rename             (const gchar *oldfilename, const gchar *newfilename);

A wrapper for the POSIX rename() function. The rename() function renames a file, moving it between directories if required.

See the C library manual for more details about how rename() . Note in particular that on Win9x it is not possible to rename a file if a file with the new name already exists. Also it is not possible in general on Windows to rename an open file.

g_mkdir ()

int         g_mkdir               (const gchar *filename, int mode);

A wrapper for the POSIX mkdir() function. The mkdir() function attempts to create a directory with the given name and permissions.

See the C library manual for more details about mkdir().

g_stat ()

int         g_stat              (const gchar *filename, struct stat *buf);

A wrapper for the POSIX stat() function. The stat() function returns information about a file.

See the C library manual for more details about stat().

g_lstat ()

int         g_lstat          (const gchar *filename, struct stat *buf);

A wrapper for the POSIX lstat() function. The lstat() function is like stat() except that in the case of symbolic links, it returns information about the symbolic link itself and not the file that it refers to. If the system does not support symbolic links g_lstat() is identical to g_stat().

See the C library manual for more details about lstat().

g_unlink ()

int         g_unlink               (const gchar *filename);

A wrapper for the POSIX unlink() function. The unlink() function deletes a name from the filesystem. If this was the last link to the file and no processes have it opened, the diskspace occupied by the file is freed.

See the C library manual for more details about unlink(). Note that on Windows, it is in general not possible to delete files that are open to some process, or mapped into memory.

g_remove ()

int         g_remove               (const gchar *filename);

A wrapper for the POSIX remove() function. The remove() function deletes a name from the filesystem.

See the C library manual for more details about remove(). On Unix, remove() removes also directories, as it calls unlink() for files and rmdir() for directories. On Windows, although remove() in the C library only works for files, this function tries first remove() and then if that fails rmdir(), and thus works for both files and directories. Note however, that on Windows, it is in general not possible to remove a file that is open to some process, or mapped into memory.

If this function fails on Windows not much can be infered from the errno value. rmdir() is tried regardless of what caused remove() to fail. Any errno value set by remove() will be overwritten by that set by rmdir().

g_rmdir ()

int         g_rmdir               (const gchar *filename);

A wrapper for the POSIX rmdir() function. The rmdir() function deletes a directory from the filesystem.

See the C library manual for more details about  rmdir().

g_fopen ()

FILE*       g_fopen               (const gchar *filename, const gchar *mode);

A wrapper for the POSIX fopen() function. The fopen() function opens a file and associates a new stream with it.

See the C library manual for more details about fopen().

g_freopen ()

FILE*       g_freopen            (const gchar *filename, const gchar *mode, FILE *stream);

A wrapper for the POSIX freopen() function. The freopen() function opens a file and associates it with an existing stream.

See the C library manual for more details about freopen().

g_chmod ()

int         g_chmod             (const gchar *filename, int mode);

A wrapper for the POSIX chmod() function. The chmod() function is used to set the permissions of a file system object. Note that on Windows the file protection mechanism is not at all POSIX-like, and the underlying chmod() function in the C library just sets or clears the READONLY attribute. It does not touch any ACL. Software that needs to manage file permissions on Windows exactly should use the Win32 API.

See the C library manual for more details about chmod().

g_access ()

int         g_access            (const gchar *filename, int mode);

A wrapper for the POSIX access() function. This function is used to test a pathname for one or several of read, write or execute permissions, or just existence. On Windows, the underlying access() function in the C library only checks the READONLY attribute, and does not look at the ACL at all. Software that needs to handle file permissions on Windows more exactly should use the Win32 API.

See the C library manual for more details about access().

g_creat ()

int         g_creat               (const gchar *filename, int mode);

A wrapper for the POSIX creat() function. The creat() function is used to convert a pathname into a file descriptor, creating a file if necessar. Note that on POSIX systems file descriptors are implemented by the operating system. On Windows, it is the C library that implements creat() and file descriptors. The actual Windows API for opening files is something different.

See the C library manual for more details about creat().

g_chdir ()

int         g_chdir             (const gchar *path); 

A wrapper for the POSIX chdir() function. The function changes the current directory of the process to path.

See the C library manual for more details about chdir().