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File Utilities
File Utilities — various file-related functions
#include &glib.h&
#include &glib/gstdio.h&
( err_no);
*filename,
**contents,
*filename,
*contents,
*filename,
**name_used,
*filename,
*pathname,
int mode);
*filename,
*filename,
int flags,
int mode);
*oldfilename,
*newfilename);
*filename,
int mode);
*filename,
struct stat *buf);
*filename,
struct stat *buf);
*filename);
*filename);
*filename);
*filename,
*filename,
FILE *stream);
*filename,
int mode);
*filename,
int mode);
*filename,
int mode);
Description
There is a group of functions which wrap the common POSIX functions
dealing with filenames (, , , ,
, , , ). 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 ,
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
Values corresponding to errno codes returned from file operations
on UNIX. Unlike errno codes,
values are available on
all systems, even Windows. The exact meaning of each code depends on what
sort of file operation 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
Ope only the owner of the
file (or other resource) or processes with special privileges can
perform the operation.
G_FILE_ERROR_ISDIR
F you cannot open a directory
for writing, or create or remove hard links to it.
G_FILE_ERROR_ACCES
P 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
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
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
G_FILE_ERROR_NOSPC
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
G_FILE_ERROR_NFILE
There are too many distinct file openings in the
entire system.
G_FILE_ERROR_BADF
B 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
B there is no process reading from the
other end of a pipe.
Every library function that returns this
error code also generates a `SIGPIPE' 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 tem the call might
work if you try again later.
G_FILE_ERROR_INTR
Inter an asynchronous signal
occurred and prevented completion of the call.
happens, you should try the call again.
G_FILE_ERROR_IO
Input/ usually used for physical read
or write errors. i.e. the disk or other physical device hardware
is returning errors.
G_FILE_ERROR_PERM
Ope only the owner of the
file (or other resource) or processes with special privileges can
perform the operation.
G_FILE_ERROR_NOSYS
Func this indicates that the
system is missing some functionality.
G_FILE_ERROR_FAILED
Does not correspond to a UNIX this
is the standard "failed for unspecified reason" error code present in
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
enumeration. See
for information on
error domains.
enum GFileTest
typedef enum
G_FILE_TEST_IS_REGULAR
G_FILE_TEST_IS_SYMLINK
G_FILE_TEST_IS_DIR
G_FILE_TEST_IS_EXECUTABLE = 1 && 3,
G_FILE_TEST_EXISTS
A test to perform on a file using .
G_FILE_TEST_IS_REGULAR
if the file is a regular file (not a directory).
Note that this test will also return
if the tested file is a symlink
to a regular file.
G_FILE_TEST_IS_SYMLINK
if the file is a symlink.
G_FILE_TEST_IS_DIR
if the file is a directory.
G_FILE_TEST_IS_EXECUTABLE
if the file is executable.
G_FILE_TEST_EXISTS
if the file exists.
It may or may not be a regular file.
g_file_error_from_errno ()
g_file_error_from_errno
( err_no);
constant based on the passed-in errno.
For example, if you pass in EEXIST this function returns
. Unlike errno values, you can portably
assume that all
values will exist.
Normally a
value goes into a
from a function that manipulates files. So you would use
when constructing a .
err_no :
an "errno" value
Returns :
corresponding to the given errno
g_file_get_contents ()
g_file_get_contents
*filename,
**contents,
Reads an entire file into allocated memory, with good error
If the call was successful, it returns
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
for the length argument. If the call was not successful, it returns
and sets error. The error domain is . Possible error
codes are those in the
enumeration. In the error case,
contents is set to
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
error :
return location for a , or
Returns :
on success,
if an error occurred
g_file_set_contents ()
g_file_set_contents
*filename,
*contents,
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 sucessful, it returns . If the call was not successful,
it returns
and sets error. The error domain is .
Possible error codes are those in the
enumeration.
filename :
name of a file to write contents to, in the GLib file name
contents :
string to write to the file
length :
length of contents, or -1 if contents is a nul-terminated string
error :
return location for a , or
Returns :
on success,
if an error occurred
g_file_test ()
g_file_test
*filename,
if any of the tests in the bitfield test are
. For example, (G_FILE_TEST_EXISTS |
G_FILE_TEST_IS_DIR) will return
the check whether it's a directory doesn't matter since the existence
test is . With the current set of available tests, there's no point
passing in more than one test at a time.
Apart from
all tests follow symbolic links,
so for a symbolic link to a regular file
will return
Note, that for a dangling symbolic link
will return
for all other flags.
You should never use
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
to know whether it is safe to write to a file without being
tricked into writing into a different location. It doesn't work!
Another thing to note is that
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
will always return . Testing for
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
Returns :
whether a test was
g_mkstemp ()
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".
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
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 ()
g_file_open_tmp
**name_used,
Opens a file for writing in the preferred directory for temporary
files (as returned by ).
tmpl should be a string in the GLib file name encoding containing
a sequence of six 'X' characters, as the parameter to .
However, unlike these functions, the template should only be a
basename, no directory components are allowed. If template is
, a default template is used.
Note that in contrast to
(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-. This
string should be freed with
when not needed any longer.
The returned name is in the GLib file name encoding.
tmpl :
Template for file name, as in , basename only,
or , to a default template
name_used :
location to store actual name used
error :
return location for a
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 ()
g_file_read_link
*filename,
Reads the contents of the symbolic link filename like the POSIX
readlink() function.
The returned string is in the encoding used
for filenames. Use
to convert it to UTF-8.
filename :
the symbolic link
error :
return location for a
Returns :
A newly allocated string with the contents of the symbolic link,
if an error occurred.
g_mkdir_with_parents ()
g_mkdir_with_parents
*pathname,
int 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.
typedef struct _GDir GD
An opaque structure representing an opened directory.
g_dir_open ()
g_dir_open
Opens a directory for reading. The names of the files in the
directory can then be retrieved using .
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 , or .
If non-, an error will be set if and only if
Returns :
a newly allocated
on success,
on failure.
If non-, you must free the result with
when you are finished with it.
g_dir_read_name ()
g_dir_read_name
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 * created by
Returns :
The entry's name or
if there are no
more entries. The return value is owned by GLib and
must not be modified or freed.
g_dir_rewind ()
g_dir_rewind
Resets the given directory. The next call to
will return the first entry again.
dir :
a * created by
g_dir_close ()
g_dir_close
Closes the directory and deallocates all related resources.
dir :
a * created by
GMappedFile
typedef struct _GMappedFile GMappedF
represents a file mapping created with
. It has only private members and should
not be accessed directly.
g_mapped_file_new ()
g_mapped_file_new
*filename,
Maps a file into memory. On UNIX, this is using the mmap() function.
If writable is , 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 . 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 ).
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 , or
Returns :
a newly allocated
which must be freed
if the mapping failed.
g_mapped_file_free ()
g_mapped_file_free
Unmaps the buffer of file and frees it.
file :
g_mapped_file_get_length ()
g_mapped_file_get_length
Returns the length of the contents of a .
file :
Returns :
the length of the contents of file.
g_mapped_file_get_contents ()
g_mapped_file_get_contents
Returns the contents of a .
Note that the contents may not be zero-terminated,
even if the
is backed by a text file.
file :
Returns :
the contents of file.
*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 (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().
g_rename ()
*oldfilename,
*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 Win9x it is not possible
to rename a file if a file with the new name already exists. Also
it is not possible in general on Windows to rename an open file.
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
g_mkdir ()
*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 the 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
*filename,
struct stat *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 READONLY attribute and does not look
at the ACL at all. Thus the protection bits in the st_mode field
are a fabrication of little use.
See the 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
g_lstat ()
*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
is identical to .
See the 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
g_unlink ()
*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
g_remove ()
*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
g_rmdir ()
*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
g_fopen ()
*filename,
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 (UTF-8 on Windows)
mode :
a string describing the mode in which the file should be
Returns :
A FILE pointer if the file was successfully
opened, or
if an error occurred
g_freopen ()
*filename,
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 (UTF-8 on Windows)
mode :
a string describing the mode in which the file should be
stream :
an existing stream which will be reused, or
Returns :
A FILE pointer if the file was successfully
opened, or
if an error occurred.
g_chmod ()
*filename,
int mode);
A wrapper for the POSIX chmod() function. The chmod() function is
used to set the permissions of a file system object. Note that on
Windows the file protection mechanism is not at all POSIX-like, and
the underlying chmod() function in the C library just sets or
clears the READONLY attribute. It does not touch any ACL. Software
that needs to manage file permissions on Windows exactly should
use the Win32 API.
See the C library manual for more details about chmod().
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.
g_access ()
*filename,
int mode);
A wrapper for the POSIX access() function. This function is used to
test a pathname for one or several of read, write or execute
permissions, or just existence. On Windows, the underlying access()
function in the C library only checks the READONLY attribute, and
does not look at the ACL at all. Software that needs to handle file
permissions on Windows more exactly should use the Win32 API.
See the C library manual for more details about access().
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
g_creat ()
*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. Note that 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 something different.
See the 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().
g_chdir ()
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.