GLib Reference Manual: File Utilities

## File Utilities File Utilities — various file-related functions |

## Synopsis

    #include <glib.h>
    #include <glib/gstdio.h>

    enum                GFileError;
    #define             G_FILE_ERROR
    enum                GFileTest;
    GFileError          g_file_error_from_errno             (gint err_no);
    gboolean            g_file_get_contents                 (const gchar *filename,
                                                             gchar **contents,
                                                             gsize *length,
                                                             GError **error);
    gboolean            g_file_set_contents                 (const gchar *filename,
                                                             const gchar *contents,
                                                             gssize length,
                                                             GError **error);
    gboolean            g_file_test                         (const gchar *filename,
                                                             GFileTest test);
    gint                g_mkstemp                           (gchar *tmpl);
    gint                g_mkstemp_full                      (gchar *tmpl,
                                                             gint flags,
                                                             gint mode);
    gint                g_file_open_tmp                     (const gchar *tmpl,
                                                             gchar **name_used,
                                                             GError **error);
    gchar *             g_file_read_link                    (const gchar *filename,
                                                             GError **error);
    gint                g_mkdir_with_parents                (const gchar *pathname,
                                                             gint mode);
    gchar *             g_mkdtemp                           (gchar *tmpl);
    gchar *             g_mkdtemp_full                      (gchar *tmpl,
                                                             gint mode);
    gchar *             g_dir_make_tmp                      (const gchar *tmpl,
                                                             GError **error);

                        GDir;
    GDir *              g_dir_open                          (const gchar *path,
                                                             guint flags,
                                                             GError **error);
    const gchar *       g_dir_read_name                     (GDir *dir);
    void                g_dir_rewind                        (GDir *dir);
    void                g_dir_close                         (GDir *dir);

                        GMappedFile;
    GMappedFile *       g_mapped_file_new                   (const gchar *filename,
                                                             gboolean writable,
                                                             GError **error);
    GMappedFile *       g_mapped_file_new_from_fd           (gint fd,
                                                             gboolean writable,
                                                             GError **error);
    GMappedFile *       g_mapped_file_ref                   (GMappedFile *file);
    void                g_mapped_file_unref                 (GMappedFile *file);
    void                g_mapped_file_free                  (GMappedFile *file);
    gsize               g_mapped_file_get_length            (GMappedFile *file);
    gchar *             g_mapped_file_get_contents          (GMappedFile *file);
    GBytes *            g_mapped_file_get_bytes             (GMappedFile *file);

    int                 g_open                              (const gchar *filename,
                                                             int flags,
                                                             int mode);
    int                 g_rename                            (const gchar *oldfilename,
                                                             const gchar *newfilename);
    int                 g_mkdir                             (const gchar *filename,
                                                             int mode);
    typedef             GStatBuf;
    int                 g_stat                              (const gchar *filename,
                                                             GStatBuf *buf);
    int                 g_lstat                             (const gchar *filename,
                                                             GStatBuf *buf);
    int                 g_unlink                            (const gchar *filename);
    int                 g_remove                            (const gchar *filename);
    int                 g_rmdir                             (const gchar *filename);
    FILE *              g_fopen                             (const gchar *filename,
                                                             const gchar *mode);
    FILE *              g_freopen                           (const gchar *filename,
                                                             const gchar *mode,
                                                             FILE *stream);
    int                 g_chmod                             (const gchar *filename,
                                                             int mode);
    int                 g_access                            (const gchar *filename,
                                                             int mode);
    int                 g_creat                             (const gchar *filename,
                                                             int mode);
    int                 g_chdir                             (const gchar *path);
    int                 g_utime                             (const gchar *filename,
                                                             struct utimbuf *utb);
    gboolean            g_close                             (gint fd,
                                                             GError **error);

## Description

There is a group of functions which wrap the common POSIX functions dealing with filenames (`g_open()`, `g_rename()`, `g_mkdir()`, `g_stat()`, `g_unlink()`, `g_remove()`, `g_fopen()`, `g_freopen()`). The point of these wrappers is to make it possible to handle file names with any Unicode characters in them on Windows without having to use ifdefs and the wide character API in the application code.

The pathname argument should be in the GLib file name encoding. On POSIX this is the actual on-disk encoding which might correspond to the locale settings of the process (or the `G_FILENAME_ENCODING` environment variable), or not.

On Windows the GLib file name encoding is UTF-8. Note that the Microsoft C library does not use UTF-8, but has separate APIs for current system code page and wide characters (UTF-16). The GLib wrappers call the wide character API if present (on modern Windows systems), otherwise convert to/from the system code page.

Another group of functions allows to open and read directories in the GLib file name encoding. These are `g_dir_open()`, `g_dir_read_name()`, `g_dir_rewind()`, `g_dir_close()`.

## Details

### 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 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_EXIST` | Operation not permitted; only the owner of the file (or other resource) or processes with special privileges can perform the operation.
`G_FILE_ERROR_ISDIR` | File is a directory; you cannot open a directory for writing, or create or remove hard links to it.
`G_FILE_ERROR_ACCES` | Permission denied; the file permissions do not allow the attempted operation.
`G_FILE_ERROR_NAMETOOLONG` | Filename too long.
`G_FILE_ERROR_NOENT` | No such file or directory. This is a "file doesn't exist" error for ordinary files that are referenced in contexts where they are expected to already exist.
`G_FILE_ERROR_NOTDIR` | A file that isn't a directory was specified when a directory is required.
`G_FILE_ERROR_NXIO` | No such device or address. The system tried to use the device represented by a file you specified, and it couldn't find the device. This can mean that the device file was installed incorrectly, or that the physical device is missing or not correctly attached to the computer.
`G_FILE_ERROR_NODEV` | The underlying file system of the specified file does not support memory mapping.
`G_FILE_ERROR_ROFS` | The directory containing the new link can't be modified because it's on a read-only file system.
`G_FILE_ERROR_TXTBSY` | Text file busy.
`G_FILE_ERROR_FAULT` | You passed in a pointer to bad memory. (GLib won't reliably return this, don't pass in pointers to bad memory.)
`G_FILE_ERROR_LOOP` | Too many levels of symbolic links were encountered in looking up a file name. This often indicates a cycle of symbolic links.
`G_FILE_ERROR_NOSPC` | No space left on device; write operation on a file failed because the disk is full.
`G_FILE_ERROR_NOMEM` | No memory available. The system cannot allocate more virtual memory because its capacity is full.
`G_FILE_ERROR_MFILE` | The current process has too many files open and can't open any more. Duplicate descriptors do count toward this limit.
`G_FILE_ERROR_NFILE` | There are too many distinct file openings in the entire system.
`G_FILE_ERROR_BADF` | Bad file descriptor; for example, I/O on a descriptor that has been closed or reading from a descriptor open only for writing (or vice versa).
`G_FILE_ERROR_INVAL` | Invalid argument. This is used to indicate various kinds of problems with passing the wrong argument to a library function.
`G_FILE_ERROR_PIPE` | Broken pipe; there is no process reading from the other end of a pipe. Every library function that returns this error code also generates a 'SIGPIPE' signal; this signal terminates the program if not handled or blocked. Thus, your program will never actually see this code unless it has handled or blocked 'SIGPIPE'.
`G_FILE_ERROR_AGAIN` | Resource temporarily unavailable; the call might work if you try again later.
`G_FILE_ERROR_INTR` | Interrupted function call; an asynchronous signal occurred and prevented completion of the call. When this happens, you should try the call again.
`G_FILE_ERROR_IO` | Input/output error; usually used for physical read or write errors. i.e. the disk or other physical device hardware is returning errors.
`G_FILE_ERROR_PERM` | Operation not permitted; only the owner of the file (or other resource) or processes with special privileges can perform the operation.
`G_FILE_ERROR_NOSYS` | Function not implemented; this indicates that the system is missing some functionality.
`G_FILE_ERROR_FAILED` | Does not correspond to a UNIX error code; this is the standard "failed for unspecified reason" error code present in all GError error code enumerations. Returned if no specific code applies.

### 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_TEST_IS_REGULAR` | `TRUE` if the file is a regular file (not a directory). Note that this test will also return `TRUE` if the tested file is a symlink to a regular file.
`G_FILE_TEST_IS_SYMLINK` | `TRUE` if the file is a symlink.
`G_FILE_TEST_IS_DIR` | `TRUE` if the file is a directory.
`G_FILE_TEST_IS_EXECUTABLE` | `TRUE` if the file is executable.
`G_FILE_TEST_EXISTS` | `TRUE` if the file exists. It may or may not be a regular file.

### 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.

`err_no` : | an "errno" value
Returns : | GFileError corresponding to the given `errno`

### 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.

`filename` : | name of a file to read contents from, in the GLib file name encoding. [type filename]
`contents` : | location to store an allocated string, use `g_free()` to free the returned string. [out][array length=length][element-type guint8]
`length` : | location to store length in bytes of the contents, or `NULL`. [allow-none]
`error` : | return location for a GError, or `NULL`
Returns : | `TRUE` on success, `FALSE` if an error occurred

### 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:

- 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 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`.

`filename` : | name of a file to write `contents` to, in the GLib file name encoding. [type filename]
`contents` : | string to write to the file. [array length=length][element-type guint8]
`length` : | length of `contents`, or -1 if `contents` is a nul-terminated string
`error` : | return location for a GError, or `NULL`
Returns : | `TRUE` on success, `FALSE` if an error occurred

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!

    1
    2
    3
    4
    5
    6
    /* 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.

`filename` : | a filename to test in the GLib file name encoding
`test` : | bitfield of GFileTest flags
Returns : | whether a test was `TRUE`

### 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.

`tmpl` : | template filename. [type filename]
Returns : | A file handle (as from `open()`) to the file opened for reading and writing. The file is opened in binary mode on platforms where there is a difference. The file handle should be closed with `close()`. In case of errors, -1 is returned and `errno` will be set.

### 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.

`tmpl` : | template filename. [type filename]
`flags` : | flags to pass to an `open()` call in addition to O_EXCL and O_CREAT, which are passed automatically
`mode` : | permissions to create the temporary file with
Returns : | A file handle (as from `open()`) to the file opened for reading and writing. The file handle should be closed with `close()`. In case of errors, -1 is returned and `errno` will be set.

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.

`tmpl` : | Template for file name, as in `g_mkstemp()`, basename only, or `NULL` for a default template. [type filename][allow-none]
`name_used` : | location to store actual name used, or `NULL`. [out][type filename]
`error` : | return location for a GError
Returns : | A file handle (as from `open()`) to the file opened for reading and writing. The file is opened in binary mode on platforms where there is a difference. The file handle should be closed with `close()`. In case of errors, -1 is returned and `error` will be set.

### 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.

`filename` : | the symbolic link
`error` : | return location for a GError
Returns : | A newly-allocated string with the contents of the symbolic link, or `NULL` if an error occurred.

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.

`pathname` : | a pathname in the GLib file name encoding
`mode` : | permissions to use for newly created directories
Returns : | 0 if the directory already exists, or was successfully created. Returns -1 if an error occurred, with errno set.

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.

`tmpl` : | template directory name. [type filename]
Returns : | A pointer to `tmpl`, which has been modified to hold the directory name. In case of errors, `NULL` is returned and `errno` will be set.

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.

`tmpl` : | template directory name. [type filename]
`mode` : | permissions to create the temporary directory with
Returns : | A pointer to `tmpl`, which has been modified to hold the directory name. In case of errors, `NULL` is returned, and `errno` will be set.

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.

`tmpl` : | Template for directory name, as in `g_mkdtemp()`, basename only, or `NULL` for a default template. [type filename][allow-none]
`error` : | return location for a GError
Returns : | The actual name used. This string should be freed with `g_free()` when not needed any longer and is is in the GLib file name encoding. In case of errors, `NULL` is returned and `error` will be set. [type filename]

Since 2.30

### 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()`. Note that the ordering is not defined.

`path` : | the path to the directory you are interested in. On Unix in the on-disk encoding. On Windows in UTF-8
`flags` : | Currently must be set to 0. Reserved for future use.
`error` : | return location for a GError, or `NULL`. If non-`NULL`, an error will be set if and only if `g_dir_open()` fails.
Returns : | a newly allocated GDir on success, `NULL` on failure. If non-`NULL`, you must free the result with `g_dir_close()` when you are finished with it.

### 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.

`dir` : | a GDir* created by `g_dir_open()`
Returns : | The entry's name or `NULL` if there are no more entries. The return value is owned by GLib and must not be modified or freed.

### 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.

`dir` : | a GDir* created by `g_dir_open()`

### g_dir_close ()

    void                g_dir_close                         (GDir *dir);

Closes the directory and deallocates all related resources.

`dir` : | a GDir* created by `g_dir_open()`

### 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()`).

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.

`filename` : | The path of the file to load, in the GLib filename encoding
`writable` : | whether the mapping should be writable
`error` : | return location for a GError, or `NULL`
Returns : | a newly allocated GMappedFile which must be unref'd with `g_mapped_file_unref()`, or `NULL` if the mapping failed.

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()`).

`fd` : | The file descriptor of the file to load
`writable` : | whether the mapping should be writable
`error` : | return location for a GError, or `NULL`
Returns : | a newly allocated GMappedFile which must be unref'd with `g_mapped_file_unref()`, or `NULL` if the mapping failed.

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.

`file` : | a GMappedFile
Returns : | the passed in GMappedFile.

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

`file` : | a GMappedFile

### g_mapped_file_free ()

    void                g_mapped_file_free                  (GMappedFile *file);

### Warning

`g_mapped_file_free` has been deprecated since version 2.22 and should not be used in newly-written code. Use `g_mapped_file_unref()` instead.

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

`file` : | a GMappedFile

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.

`file` : | a GMappedFile
Returns : | the length of the contents of `file`.

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.

`file` : | a GMappedFile
Returns : | the contents of `file`, or `NULL`.

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.

`file` : | a GMappedFile
Returns : | A newly allocated GBytes referencing data from `file`. [transfer full]

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()`.

`filename` : | a pathname in the GLib file name encoding (UTF-8 on Windows)
`flags` : | as in `open()`
`mode` : | as in `open()`
Returns : | a new file descriptor, or -1 if an error occurred. The return value can be used exactly like the return value from `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.

`oldfilename` : | a pathname in the GLib file name encoding (UTF-8 on Windows)
`newfilename` : | a pathname in the GLib file name encoding
Returns : | 0 if the renaming succeeded, -1 if an error occurred

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()`.

`filename` : | a pathname in the GLib file name encoding (UTF-8 on Windows)
`mode` : | permissions to use for the newly created directory
Returns : | 0 if the directory was successfully created, -1 if an error occurred

Since 2.6

### 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.

### 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()`.

`filename` : | a pathname in the GLib file name encoding (UTF-8 on Windows)
`buf` : | a pointer to a stat struct, which will be filled with the file information
Returns : | 0 if the information was successfully retrieved, -1 if an error occurred

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()`.

`filename` : | a pathname in the GLib file name encoding (UTF-8 on Windows)
`buf` : | a pointer to a stat struct, which will be filled with the file information
Returns : | 0 if the information was successfully retrieved, -1 if an error occurred

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.

`filename` : | a pathname in the GLib file name encoding (UTF-8 on Windows)
Returns : | 0 if the name was successfully deleted, -1 if an error occurred

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()`.

`filename` : | a pathname in the GLib file name encoding (UTF-8 on Windows)
Returns : | 0 if the file was successfully removed, -1 if an error occurred

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.

`filename` : | a pathname in the GLib file name encoding (UTF-8 on Windows)
Returns : | 0 if the directory was successfully removed, -1 if an error occurred

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 partof the FILE struct, the FILE pointer 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 pointer 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()`.

`filename` : | a pathname in the GLib file name encoding (UTF-8 on Windows)
`mode` : | a string describing the mode in which the file should be opened
Returns : | A FILE pointer if the file was successfully opened, or `NULL` if an error occurred

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()`.

`filename` : | a pathname in the GLib file name encoding (UTF-8 on Windows)
`mode` : | a string describing the mode in which the file should be opened
`stream` : | an existing stream which will be reused, or `NULL`. [allow-none]
Returns : | A `FILE` pointer if the file was successfully opened, or `NULL` if an error occurred.

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()`.

`filename` : | a pathname in the GLib file name encoding (UTF-8 on Windows)
`mode` : | as in `chmod()`
Returns : | zero if the operation succeeded, -1 on error.

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()`.

`filename` : | a pathname in the GLib file name encoding (UTF-8 on Windows)
`mode` : | as in `access()`
Returns : | zero if the pathname refers to an existing file system object that has all the tested permissions, or -1 otherwise or on error.

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()`.

`filename` : | a pathname in the GLib file name encoding (UTF-8 on Windows)
`mode` : | as in `creat()`
Returns : | a new file descriptor, or -1 if an error occurred. The return value can be used exactly like the return value from `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()`.

`path` : | a pathname in the GLib file name encoding (UTF-8 on Windows)
Returns : | 0 on success, -1 if an error occurred.

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.

`filename` : | a pathname in the GLib file name encoding (UTF-8 on Windows)
`utb` : | a pointer to a struct utimbuf.
Returns : | 0 if the operation was successful, -1 if an error occurred

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.

`fd` : | A file descriptor
`error` : | a GError

Since 2.36