g_file_error_from_errno ()

GFileError
g_file_error_from_errno (gint err_no);

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

Normally a GFileError value goes into a GError returned from a function that manipulates files. So you would 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 nul-terminated, so for text files you can 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.

Note that the name for the temporary file is constructed by appending up to 7 characters to filename .

Since 2.8

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's a directory doesn't matter since the existence test is TRUE. With the current set of available tests, there's 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.

You should 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 you actually perform the operation. For example, you might think you could use G_FILE_TEST_IS_SYMLINK to know whether it is safe to write to a file without being tricked into writing into a different location. It doesn't work!

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// 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 doesn't matter, but if your program is setuid or setgid it means that these tests will give you 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.

The parameter is a string that should follow the rules for mkstemp() templates, i.e. contain the string "XXXXXX". g_mkstemp() is slightly more flexible than mkstemp() in that the sequence does not have to occur at the very end of the template. The X string will be modified to form the name of a file that didn't exist. The string should be in the GLib file name encoding. Most importantly, on Windows it should be in UTF-8.

g_mkstemp_full ()

gint
g_mkstemp_full (gchar *tmpl,
                gint flags,
                gint mode);

Opens a temporary file. See the mkstemp() documentation on most UNIX-like systems.

The parameter is a string that should follow the rules for mkstemp() templates, i.e. contain the string "XXXXXX". g_mkstemp_full() is slightly more flexible than mkstemp() in that the sequence does not have to occur at the very end of the template and you can pass a mode and additional flags . The X string will be modified to form the name of a file that didn't exist. The string should be in the GLib file name encoding. Most importantly, on Windows it should be in UTF-8.

Since 2.22

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 containing a sequence of six 'X' characters, as the parameter to g_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.

Upon success, and if name_used is non-NULL, the actual name used is returned in name_used . 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.

Since 2.4

g_mkdir_with_parents ()

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

Create a directory if it doesn't already exist. Create intermediate parent directories as needed, too.

Since 2.8

g_mkdtemp ()

gchar *
g_mkdtemp (gchar *tmpl);

Creates a temporary directory. See the mkdtemp() documentation on most UNIX-like systems.

The parameter is a string that should follow the rules for mkdtemp() templates, i.e. contain the string "XXXXXX". g_mkdtemp() is slightly more flexible than mkdtemp() in that the sequence does not have to occur at the very end of the template and you can pass a mode and additional flags . The X string will be modified to form the name of a directory that didn't exist. The string should be in the GLib file name encoding. Most importantly, on Windows it should be in UTF-8.

Since 2.30

g_mkdtemp_full ()

gchar *
g_mkdtemp_full (gchar *tmpl,
                gint mode);

Creates a temporary directory. See the mkdtemp() documentation on most UNIX-like systems.

The parameter is a string that should follow the rules for mkdtemp() templates, i.e. contain the string "XXXXXX". g_mkdtemp() is slightly more flexible than mkdtemp() in that the sequence does not have to occur at the very end of the template and you can pass a mode . The X string will be modified to form the name of a directory that didn't exist. The string should be in the GLib file name encoding. Most importantly, on Windows it should be in UTF-8.

Since 2.30

g_dir_make_tmp ()

gchar *
g_dir_make_tmp (const gchar *tmpl,
                GError **error);

Creates a subdirectory 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 containing a sequence of six 'X' characters, as the parameter to g_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_mkdtemp() (and mkdtemp()) tmpl is not modified, and might thus be a read-only literal string.

Since 2.30

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(). Note that the ordering is not defined.

g_dir_read_name ()

const gchar *
g_dir_read_name (GDir *dir);

Retrieves the name of another entry in the directory, or NULL. The order of entries returned from this function is not defined, and may vary by file system or other operating-system dependent factors.

NULL may also be returned in case of errors. On Unix, you can check errno to find out if NULL was returned because of an error.

On Unix, the '.' and '..' entries are omitted, and the returned name is in the on-disk encoding.

On Windows, as is true of all GLib functions which operate on filenames, the returned name is in UTF-8.

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.

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()).

If filename is the name of an empty, regular file, the function will successfully return an empty GMappedFile. In other cases of size 0 (e.g. device files such as /dev/null), error will be set to the GFileError value G_FILE_ERROR_INVAL.

Since 2.8

g_mapped_file_new_from_fd ()

GMappedFile *
g_mapped_file_new_from_fd (gint fd,
                           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()).

Since 2.32

g_mapped_file_ref ()

GMappedFile *
g_mapped_file_ref (GMappedFile *file);

Increments the reference count of file by one. It is safe to call this function from any thread.

Since 2.22

g_mapped_file_unref ()

void
g_mapped_file_unref (GMappedFile *file);

Decrements the reference count of file by one. If the reference count drops to 0, unmaps the buffer of file and frees it.

It is safe to call this function from any thread.

Since 2.22

g_mapped_file_free ()

void
g_mapped_file_free (GMappedFile *file);

This call existed before GMappedFile had refcounting and is currently exactly the same as g_mapped_file_unref().

Since 2.8

g_mapped_file_get_length ()

gsize
g_mapped_file_get_length (GMappedFile *file);

Returns the length of the contents of a GMappedFile.

Since 2.8

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.

If the file is empty then NULL is returned.

Since 2.8

g_mapped_file_get_bytes ()

GBytes *
g_mapped_file_get_bytes (GMappedFile *file);

Creates a new GBytes which references the data mapped from file . The mapped contents of the file must not be modified after creating this bytes object, because a GBytes should be immutable.

Since 2.34

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.

On POSIX systems file descriptors are implemented by the operating system. On Windows, it's the C library that implements open() and file descriptors. The actual Win32 API for opening files is quite different, see MSDN documentation for CreateFile(). The Win32 API uses file handles, which are more randomish integers, not small integers like file descriptors.

Because file descriptors are specific to the C library on Windows, the file descriptor returned by this function makes sense only to functions in the same C library. Thus if the GLib-using code uses a different C library than GLib does, the file descriptor returned by this function cannot be passed to C library functions like write() or read().

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

Since 2.6

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 your C library manual for more details about how rename() works on your system. It is not possible in general on Windows to rename a file that is open to some process.

Since 2.6

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. The mode argument is ignored on Windows.

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

Since 2.6

g_stat ()

int
g_stat (const gchar *filename,
        GStatBuf *buf);

A wrapper for the POSIX stat() function. The stat() function returns information about a file. On Windows the stat() function in the C library checks only the FAT-style READONLY attribute and does not look at the ACL at all. Thus on Windows the protection bits in the st_mode field are a fabrication of little use.

On Windows the Microsoft C libraries have several variants of the stat struct and stat() function with names like _stat(), _stat32(), _stat32i64() and _stat64i32(). The one used here is for 32-bit code the one with 32-bit size and time fields, specifically called _stat32().

In Microsoft's compiler, by default struct stat means one with 64-bit time fields while in MinGW struct stat is the legacy one with 32-bit fields. To hopefully clear up this messs, the gstdio.h header defines a type GStatBuf which is the appropriate struct type depending on the platform and/or compiler being used. On POSIX it is just struct stat, but note that even on POSIX platforms, stat() might be a macro.

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

Since 2.6

g_lstat ()

int
g_lstat (const gchar *filename,
         GStatBuf *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 your C library manual for more details about lstat().

Since 2.6

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 your 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.

Since 2.6

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 your C library manual for more details about how remove() works on your system. 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 you can't infer too much 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().

Since 2.6

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 your C library manual for more details about how rmdir() works on your system.

Since 2.6

g_fopen ()

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

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

Because file descriptors are specific to the C library on Windows, and a file descriptor is part of the FILE struct, the FILE* returned by this function makes sense only to functions in the same C library. Thus if the GLib-using code uses a different C library than GLib does, the FILE* returned by this function cannot be passed to C library functions like fprintf() or fread().

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

Since 2.6

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 your C library manual for more details about freopen().

Since 2.6

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.

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 FAT-style READONLY attribute. It does not touch any ACL. Software that needs to manage file permissions on Windows exactly should use the Win32 API.

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

Since 2.8

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 file protection mechanism is not at all POSIX-like, and the underlying function in the C library only checks the FAT-style READONLY attribute, and does not look at the ACL of a file at all. This function is this in practise almost useless on Windows. Software that needs to handle file permissions on Windows more exactly should use the Win32 API.

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

Since 2.8

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 necessary.

On POSIX systems file descriptors are implemented by the operating system. On Windows, it's the C library that implements creat() and file descriptors. The actual Windows API for opening files is different, see MSDN documentation for CreateFile(). The Win32 API uses file handles, which are more randomish integers, not small integers like file descriptors.

Because file descriptors are specific to the C library on Windows, the file descriptor returned by this function makes sense only to functions in the same C library. Thus if the GLib-using code uses a different C library than GLib does, the file descriptor returned by this function cannot be passed to C library functions like write() or read().

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

Since 2.8

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 your C library manual for more details about chdir().

Since 2.8

g_utime ()

int
g_utime (const gchar *filename,
         struct utimbuf *utb);

A wrapper for the POSIX utime() function. The utime() function sets the access and modification timestamps of a file.

See your C library manual for more details about how utime() works on your system.

Since 2.18

g_close ()

gboolean
g_close (gint fd,
         GError **error);

This wraps the close() call; in case of error, errno will be preserved, but the error will also be stored as a GError in error .

Besides using GError, there is another major reason to prefer this function over the call provided by the system; on Unix, it will attempt to correctly handle EINTR, which has platform-specific semantics.

Since 2.36

enum 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 you were performing; 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

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

GDir

typedef struct _GDir GDir;

An opaque structure representing an opened directory.

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.

GStatBuf

typedef struct _stat32 GStatBuf;

A type corresponding to the appropriate struct type for the stat() system call, depending on the platform and/or compiler being used.

See g_stat() for more information.