File System

File and path utilities: existence checks, permissions, mkdir/rmdir, copy/move, size, mtime, and safe path building.

Source code:

`file_exists()`¶

The file_exists() function checks if a given file exists within a specified directory and is a regular file.

BOOL file_exists(
    const char *directory,
    const char *filename
);

Parameters

Key	Type	Description
`directory`	`const char *`	The path to the directory where the file is expected to be located.
`filename`	`const char *`	The name of the file to check for existence.

Returns

Returns TRUE if the file exists and is a regular file, otherwise returns FALSE.

Notes

This function constructs the full file path by combining directory and filename, then checks if the file exists and is a regular file using is_regular_file().

`file_permission()`¶

The file_permission() function retrieves the permission mode of a specified file path.

mode_t file_permission(const char *path);

Parameters

Key	Type	Description
`path`	`const char *`	The file path whose permission mode is to be retrieved.

Returns

Returns the permission mode of the file as a mode_t value. If the file does not exist or an error occurs, returns 0.

Notes

This function internally uses stat() to obtain the file’s mode and extracts the permission bits using bitwise operations.

`file_remove()`¶

file_remove() deletes a specified file from a given directory if it exists and is a regular file.

int file_remove(
    const char *directory,
    const char *filename
);

Parameters

Key	Type	Description
`directory`	`const char *`	The path to the directory containing the file.
`filename`	`const char *`	The name of the file to be removed.

Returns

Returns 0 on success, or -1 if the file does not exist or is not a regular file.

Notes

This function checks if the file exists and is a regular file before attempting to delete it.

`file_size()`¶

file_size() returns the size of a file in bytes, given its path.

off_t file_size(const char *path);

Parameters

Key	Type	Description
`path`	`const char *`	Path to the file whose size is to be determined.

Returns

Returns the file size in bytes on success. Returns 0 if the file does not exist or an error occurs.

Notes

This function uses stat() to retrieve file information. If stat() fails, the function returns 0.

`filesize()`¶

filesize() returns the size of a file in bytes by using the stat() system call.

off_t filesize(const char *path);

Parameters

Key	Type	Description
`path`	`const char *`	Path to the file whose size is to be determined.

Returns

Returns the size of the file in bytes. If the file does not exist or an error occurs, returns 0.

Notes

This function relies on stat(), which may fail if the file does not exist or if there are insufficient permissions.

`filesize2()`¶

filesize2() returns the size of an open file descriptor in bytes.

off_t filesize2(int fd);

Parameters

Key	Type	Description
`fd`	`int`	The file descriptor of the open file.

Returns

Returns the size of the file in bytes. If an error occurs, returns 0.

Notes

This function uses fstat() to retrieve the file size.

`is_directory()`¶

The is_directory() function checks whether the given path corresponds to a directory by using the stat() system call.

BOOL is_directory(const char *path);

Parameters

Key	Type	Description
`path`	`const char *`	The file system path to check.

Returns

Returns TRUE if the path is a directory, otherwise returns FALSE.

Notes

This function relies on stat() to determine the file type. If stat() fails, the function returns FALSE.

`is_regular_file()`¶

The is_regular_file() function checks if the given path corresponds to a regular file.

BOOL is_regular_file(const char *path);

Parameters

Key	Type	Description
`path`	`const char *`	The file system path to check.

Returns

Returns TRUE if the path corresponds to a regular file, otherwise returns FALSE.

Notes

[‘This function uses stat() to determine the file type.’, ‘If stat() fails, the function returns FALSE.’]

`lock_file()`¶

The lock_file() function applies an advisory write lock to the specified file descriptor using the fcntl system call.

int lock_file(int fd);

Parameters

Key	Type	Description
`fd`	`int`	The file descriptor of the file to be locked.

Returns

Returns 0 on success. On failure, returns -1 and sets errno to indicate the error.

Notes

This function uses fcntl with F_SETLKW to apply a blocking write lock. Ensure that the file descriptor is valid before calling this function.

`mkrdir()`¶

mkrdir() creates a directory and all its parent directories if they do not exist, similar to the mkdir -p command.

int mkrdir(
    const char *path,
    int xpermission
);

Parameters

Key	Type	Description
`path`	`const char *`	The directory path to be created.
`xpermission`	`int`	The permission mode for the created directories.

Returns

Returns 0 on success, or -1 if an error occurs.

Notes

If a directory in the path already exists, it is not modified. The function ensures that all parent directories are created as needed.

`newdir()`¶

newdir() creates a new directory with the specified permissions, ensuring that the umask is set to zero for controlled permission handling.

int newdir(
    const char *path,
    int xpermission
);

Parameters

Key	Type	Description
`path`	`const char *`	The path of the directory to be created.
`xpermission`	`int`	The permission mode for the new directory.

Returns

Returns 0 on success, or -1 if an error occurs.

Notes

This function ensures that the umask is cleared before creating the directory to allow precise permission control.

`newfile()`¶

newfile() creates a new file with the specified permissions, optionally overwriting an existing file.

int newfile(
    const char *path,
    int rpermission,
    BOOL overwrite
);

Parameters

Key	Type	Description
`path`	`const char *`	The file path to create.
`permission`	`int`	The file permission mode (e.g., 0660).
`overwrite`	`BOOL`	If `TRUE`, an existing file will be truncated; otherwise, creation fails if the file exists.

Returns

Returns a file descriptor on success, or -1 on failure.

Notes

This function sets umask(0) to ensure the specified permissions are applied.

`open_exclusive()`¶

open_exclusive() opens a file with exclusive access, ensuring that no other process can lock it simultaneously.

int open_exclusive(
    const char *path,
    int flags,
    int rpermission
);

Parameters

Key	Type	Description
`path`	`const char *`	The file path to be opened.
`flags`	`int`	Flags for opening the file. If set to 0, default flags (`O_RDWR \| O_NOFOLLOW`) are used.
`permission`	`int`	The file permission mode, used when creating a new file.

Returns

Returns a file descriptor on success, or -1 on failure.

Notes

This function applies an exclusive lock (LOCK_EX | LOCK_NB) to the file, ensuring that no other process can acquire a lock on it.

`rmrcontentdir()`¶

The function rmrcontentdir recursively removes the contents of a directory without deleting the directory itself.

int rmrcontentdir(const char *root_dir);

Parameters

Key	Type	Description
`root_dir`	`const char *`	Path to the directory whose contents should be removed.

Returns

Returns 0 on success, or -1 if an error occurs.

Notes

This function does not remove the root directory itself, only its contents. It skips special entries like . and .. and handles both files and subdirectories recursively.

`rmrdir()`¶

rmrdir() recursively removes a directory and all its contents, including subdirectories and files.

int rmrdir(
    const char *root_dir
);

Parameters

Key	Type	Description
`path`	`const char *`	The path of the directory to be removed.

Returns

Returns 0 on success, or -1 if an error occurs.

Notes

This function removes all files and subdirectories within the specified directory before deleting the directory itself.

`subdir_exists()`¶

Checks if a given subdirectory exists within a specified directory.

BOOL subdir_exists(
    const char *directory,
    const char *subdir
);

Parameters

Key	Type	Description
`directory`	`const char *`	The path of the parent directory.
`subdir`	`const char *`	The name of the subdirectory to check.

Returns

Returns TRUE if the subdirectory exists, otherwise returns FALSE.

Notes

This function constructs the full path of the subdirectory and verifies its existence using is_directory().

`unlock_file()`¶

The unlock_file() function releases an advisory lock on a file descriptor using the fcntl system call.

int unlock_file(int fd);

Parameters

Key	Type	Description
`fd`	`int`	The file descriptor of the file to be unlocked.

Returns

Returns 0 on success, or -1 if an error occurs.

Notes

This function is typically used in conjunction with lock_file() to manage file locking in multi-process environments.

`copyfile()`¶

Copies a file from source to destination using kernel-space operations for efficiency.

int copyfile(
    const char* source,
    const char* destination,
    int permission,
    BOOL overwrite
);

Parameters

Key	Type	Description
`source`	`const char *`	Path to the source file.
`destination`	`const char *`	Path to the destination file.
`permission`	`int`	The permission mode for the destination file.
`overwrite`	`BOOL`	If `TRUE`, an existing destination file will be overwritten; otherwise, the copy fails if the file exists.

Returns

Returns 0 on success, or -1 on error.

`read_process_cmdline()`¶

Reads the command-line arguments of a process into a buffer.

int read_process_cmdline(
    char *bf,
    size_t bfsize,
    pid_t pid
);

Parameters

Key	Type	Description
`bf`	`char *`	Buffer to receive the command-line string.
`bfsize`	`size_t`	Size of the buffer in bytes.
`pid`	`pid_t`	Process ID to read. Pass `0` for the current process.

Returns

Returns 0 on success, or -1 on error.

Notes

On Linux, this function reads from /proc/[pid]/cmdline.

`set_cloexec()`¶

Sets the FD_CLOEXEC flag on a file descriptor to prevent inheritance by child processes.

int set_cloexec(
    int fd
);

Parameters

Key	Type	Description
`fd`	`int`	The file descriptor to modify.

Returns

Returns 0 on success, or -1 on error.

`set_nonblocking()`¶

Sets a file descriptor to non-blocking mode.

int set_nonblocking(
    int fd
);

Parameters

Key	Type	Description
`fd`	`int`	The file descriptor to set to non-blocking mode.

Returns

Returns 0.

file_exists()¶

file_permission()¶

file_remove()¶

file_size()¶

filesize()¶

filesize2()¶

is_directory()¶

is_regular_file()¶

lock_file()¶

mkrdir()¶

newdir()¶

newfile()¶

open_exclusive()¶

rmrcontentdir()¶

rmrdir()¶

subdir_exists()¶

unlock_file()¶

copyfile()¶

read_process_cmdline()¶

set_cloexec()¶

set_nonblocking()¶

`file_exists()`¶

`file_permission()`¶

`file_remove()`¶

`file_size()`¶

`filesize()`¶

`filesize2()`¶

`is_directory()`¶

`is_regular_file()`¶

`lock_file()`¶

`mkrdir()`¶

`newdir()`¶

`newfile()`¶

`open_exclusive()`¶

`rmrcontentdir()`¶

`rmrdir()`¶

`subdir_exists()`¶

`unlock_file()`¶

`copyfile()`¶

`read_process_cmdline()`¶

`set_cloexec()`¶

`set_nonblocking()`¶