since: 2.66


g_file_set_contents_full (
  const gchar* filename,
  const gchar* contents,
  gssize length,
  GFileSetContentsFlags flags,
  int mode,
  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.

flags control the properties of the write operation: whether it’s atomic, and what the tradeoff is between returning quickly or being resilient to system crashes.

As this function performs file I/O, it is recommended to not call it anywhere where blocking would cause problems, such as in the main loop of a graphical application. In particular, if flags has any value other than G_FILE_SET_CONTENTS_NONE then this function may call fsync().

If G_FILE_SET_CONTENTS_CONSISTENT is set in flags, the operation is atomic in the sense that it is first written to a temporary file which is then renamed to the final name.


  • On UNIX, if filename already exists hard links to filename will break. Also since the file is recreated, existing permissions, access control lists, metadata etc. may be lost. If filename is a symbolic link, the link itself will be replaced, not the linked file.

  • On UNIX, if filename already exists and is non-empty, and if the system supports it (via a journalling filesystem or equivalent), and if G_FILE_SET_CONTENTS_CONSISTENT is set in flags, the fsync() call (or equivalent) will be used to ensure atomic replacement: filename will contain either its old contents or contents, even in the face of system power loss, the disk being unsafely removed, etc.

  • On UNIX, if filename does not already exist or is empty, there is a possibility that system power loss etc. after calling this function will leave filename empty or full of NUL bytes, depending on the underlying filesystem, unless G_FILE_SET_CONTENTS_DURABLE and G_FILE_SET_CONTENTS_CONSISTENT are set in flags.

  • On Windows renaming a file will not remove an existing file with the new name, so on Windows there is a race condition between the existing file being removed and the temporary file being renamed.

  • On Windows there is no way to remove a file that is open to some process, or mapped into memory. Thus, this function will fail if filename already exists and is open.

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.

If the file didn’t exist before and is created, it will be given the permissions from mode. Otherwise, the permissions of the existing file may be changed to mode depending on flags, or they may remain unchanged.

Available since: 2.66



Type: const gchar*

Name of a file to write contents to, in the GLib file name encoding.

The data is owned by the caller of the function.
The value is a file system path, using the OS encoding.

Type: An array of guint8

String to write to the file.

The length of the array is specified in the length argument.
The data is owned by the caller of the function.

Type: gssize

Length of contents, or -1 if contents is a nul-terminated string.


Type: GFileSetContentsFlags

Flags controlling the safety vs speed of the operation.


Type: int

File mode, as passed to open(); typically this will be 0666


Type: GError **

The return location for a recoverable error.

The argument can be NULL.
If the return location is not NULL, then you must initialize it to a NULL GError*.
The argument will left initialized to NULL by the function if there are no errors.
In case of error, the argument will be set to a newly allocated GError; the caller will take ownership of the data, and be responsible for freeing it.

Return value

Type: gboolean

TRUE on success, FALSE if an error occurred.