## 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_test                     (const gchar *filename,
                                                 GFileTest test);
    gint        g_mkstemp                       (gchar *tmpl);
    gint        g_file_open_tmp                 (const gchar *tmpl,
                                                 gchar **name_used,
                                                 GError **error);
    gchar*      g_file_read_link                (const gchar *filename,
                                                 GError **error);

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

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

## 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` | This file is of a type that doesn't support 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 symlink or directory)
`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 `errno`. 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
`contents` : | location to store an allocated string
`length` : | location to store length in bytes of the contents, or `NULL`
`error` : | return location for a GError, or `NULL`
Returns : | `TRUE` on success, `FALSE` if an error occurred

### 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 is safe to write to a file without being tricked into writing into a different location. It doesn't 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 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. 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 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
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.

### 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.

`tmpl` : | Template for file name, as in `g_mkstemp()`, basename only
`name_used` : | location to store actual name used
`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

### struct GDir

    struct 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()`.

`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 ()

    G_CONST_RETURN 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.

`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()`

### 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's 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()`.

`filename` : | a pathname in the GLib file name encoding
`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. Note in particular that on Windows, it is in general not possible to rename a file if a file with the new name already exists. Also it is not possible in general to rename an open file.

`oldfilename` : | a pathname in the GLib file name encoding
`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.

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

`filename` : | a pathname in the GLib file name encoding
`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

### 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()`.

`filename` : | a pathname in the GLib file name encoding
`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,
                                                 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()`.

`filename` : | a pathname in the GLib file name encoding
`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
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.

`filename` : | a pathname in the GLib file name encoding
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
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 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()`.

`filename` : | a pathname in the GLib file name encoding
`mode` : | a string describing the mode in which the file should be opened
Returns : | A <typename>FILE</typename> 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 the C library manual for more details about `freopen()`.

`filename` : | a pathname in the GLib file name encoding
`mode` : | a string describing the mode in which the file should be opened
`stream` : | an existing stream which will be reused, or `NULL`
Returns : | A <typename>FILE</typename> pointer if the file was successfully opened, or `NULL` if an error occurred.

Since 2.6