FBB::FileSystem(3bobcat)
Wraps std::filesystem
(libbobcat-dev_6.07.00)
2005-2025
NAME
FBB::Filesystem - class offering std::filesystem facilities
SYNOPSIS
#include <bobcat/filesystem>
Linking option: -lbobcat
This header file also includes the std::chrono header file.
DESCRIPTION
The Bobcat class FileSystem is a plain wrapper around the facilities
offered by the C++ std::filesystem namespace. FileSystem was
developed because the use of the std::filesystem facilities is considered
overly complex: too many free functions having signatures resembling C,
and therefore not object-based. Its std::filesystem::path type offers
several nice features which are then usable via the path member functions,
but functions manipulating the file system aren't members, but are defined as
free functions requiring path arguments.
The class FileSystem offers almost all std::filesystem facilities via
its member functions. Except for some (static) members all facilities
operate on data stored inside FileSystem objects.
The class FileSystem is an extensive class: over-all it contains about 60
constructors, operators and members. It'll probably take a while before a
mental picture of what the class offers has been attained, but at least it
embeds all components of the std::filesystem namespace.
Note:
- The class FileSystem uses std::chrono::file_clock, which is
available since the C++-2a standard: specify the --std=c++2a
(or more recent) compiler option when using FileSystem.
NAMESPACE
FBB
All constructors, members, operators and manipulators, mentioned in this
man-page, are defined in the namespace FBB.
INHERITS FROM
FBB::FS - internally used only, covered in this man-page
TYPEDEFS AND ENUMS
Typedefs:
- DirEntry - std::filesystem::directory_entry
- DirIter - std::filesystem::directory_iterator
- EC - std::error_code
- FileClock - std::chrono::file_clock
- FileType - std::filesystem::file_type
- Path - std::filesystem::path
- Perms - std::filesystem::perms
- RecursiveIter - std::filesystem::recursive_directory_iterator
- FileStatus - std::filesystem::file_status
- SystemClock - std::chrono::system_clock
FSOptions:
- enum FSOptions:
contains the following values, inherited by
FileSystem. Options up to CP_MASK are primarily
used by the copy member, options beyond CP_MASK are used by
setPermissions:
NEW copy is only performed if the destination
doesn't yet exist
REPLACE copy is only performed if the destination
exists but it is replaced
UPDATE copy is only performed if the destination
is older than the filesystem entry to copy
RECURSIVE directories are recursively copied; can be
combined with CP_SYMLINKS, SKIP_SYMLINKS,
ONLY_DIRS
CP_SYMLINKS symlinks are copied as symlinks
SKIP_SYMLINKS symlinks are ignored
ONLY_DIRS only the directory structure is copied
other entries in directories are ignored
SYMLINK with copy: define a symlink to the current
entry
HARDLINK with copy: define a hard link to the current
entry
FILE with copy: only files are processed, not
directories
CP_SYMLINK copies a symlink to a symlink
NEW_SYMLINK defines a non-existing (directory) symlink
NEW_LINK create_hard-link
CP_MASK all the above enum values
RESET replace the current permissions
ADD add to the current permissions
REMOVE remove the specified permissions
All bit-wise operators are available for FSOptions values.
STATIC DATA MEMBER
The class FileSystem defines one static data member:
std::error_code s_errorCode. All FileSystem objects can use this
error_code object after calling their function call operator. E.g.,
FileSystem fs;
fs();
Once fs() has been called members called by fs accepting
error_code arguments receive s_error_code as their argument. It's also
possible to use other error_code objects, or not to use error_code
arguments (which is the default). See also the description of the function
call operator below.
CONSTRUCTORS
Path arguments can also be arguments of types from which Path
objects can be constructed (e.g., std::string, char const *, raw string
literal).
FileSystem objects contain two data members: a Path and an
EC *. When FileSystem objects are initialized their EC * is set to
0.
- Filesystem():
The default constructor constructs an empty object, not using the
class's static s_errorCode object;
- Filesystem(Path const &path, bool useEC = true):
The object is initialized with a copy of path. By default useEC
== true, in which case it uses the class's static s_errorCode
object;
- Filesystem(Path &&path, EC &ec):
The object is initialized with a copy of path, passing ec to
members supporting EC arguments;
- Filesystem(Path const &tmp, bool useEC = true):
The object moves tmp to its internal path. By default useEC
== true, in which case it uses the class's static s_errorCode
object;
- Filesystem(Path &&tmp, EC &ec):
The object moves tmp to its internal path, passing ec to
members supporting EC arguments.
Copy and move constructors (and assignment operators) are available. The
newly constructed or assigned object use the same EC specification as
their source (right-hand side) objects.
OVERLOADED OPERATORS
Type arguments can be arguments of type FileSystem, Path or types
from which Path objects can be constructed (e.g., std::string, char
const *, raw string literal).
MEMBER FUNCTIONS
Type arguments can be arguments of type FileSystem, Path or types
from which Path objects can be constructed (e.g., std::string, char
const *, raw string literal).
All members can use EC objects to prevent exceptions being thrown when
the members cannot perform their tasks.
- FileSystem absolute() const:
returns a FileSystem object containing the absolute path of the
calling object's Path, which does not have to exist. Relative
directory specifications are kept: absolute simply prefixes the
current working directory to the calling object's Path;
- FileSystem canonical() const:
returns a FileSystem object containing the canonical absolute path
of the calling object's Path, from which all relative
specifications have been removed. Path must refer to an existing
file system entry;
- bool copy(Type const &dest, FSOptions cpOptions = DEFAULT):
copies the object's file system entry to dest. It is covered in
detail in the section COPYING FILE SYSTEM ENTRIES below;
- uintmax_t count() const:
returns the number of hard-link counts of the calling FileSystem
object. The file system entry must exist;
- char const *c_str() const:
returns the calling object's PATH specification as a NTBS;
- static FileSystem cwd([EC &ec]):
this static member returns the current working directory (cwd). If the
cwd cannot be determined then an exception is thrown, unless an EC
argument is specified, in which case the EC argument provides
information about the failure;
- FileSystem destination() const:
returns a FileSystem object containing the (symlink) destination of
the calling object, which must refer to a symlink;
- DirEntry directory() const:
returns a DirEntry for the calling object. The calling object does
not have to refer to a directory, and not even to an existing file
system entry;
- Ranger<DirIter> dirRange() const:
returns a pair of directory iterators non-recursively visiting all
entries referred to by the calling object, which must specify a
directory name (see also the member recursiveRange). Example:
for (auto const &entry: fs.dirRange())
cout << entry << '\n';
- static std::error_code &errorCode():
this static member returns a reference to FileSystem's static
(modifiable) EC data member.
- bool exists() const:
returns true if the current object's file system entry exists;
- static bool exists(FileStatus status):
returns true if status indicates that the current file system
entry exists (see also the member status below);
- std::string extension() const:
returns the extension (including the initial dot (.) of the calling
object);
- FileClock::time_point fcModification() const:
returns the FileClock::time_point of the (existing) file system
entry represented by the calling object;
- std::string filename() const:
returns the filename (i.e., the path name from which all but the last
element has been removed). If the calling object doesn't contain a
filename (as with ./ or /) then and empty string is
returned;
- bool hasExtension() const:
returns true if the calling object's Path has an extension;
- bool hasFilename() const:
returns true if the calling object's Path contains characters
after its final / character;
- bool isAbsolute() const:
returns true if the calling object's Path starts with /;
- bool isRelative() const:
returns true if the calling object's Path does not start with
/;
- bool knownStatus() const:
this member only returns false for
std::filesystem::file_status{}. The member status is probably
more useful: non-existing entries show status values
FileType::not_found or FileType::unknown.
To check for specific statuses the functions
bool is_WHATEVER(file_status status) or
bool is_WHATEVER(path const &entry [, EC &ec])
can also be used;
- bool mkDir() const:
returns true if the (plain) directory name stored in the calling
oblect could be created. This member does not create nested
sub-directories, but the directory name specified as the last
(/-separated) component of the calling object's Path is
created if its parent directories already exist;
- bool mkDir(Type const &reference) const:
same as the previous member, but the created directory receives the
same attributes (permissions) as reference;
- bool mkDirs() const:
returns true if the last component of the calling object's Path
could be created and its parent components could either be created or
already existed as directories. Only the directories are constructed,
not their entries. Use the copy member (see section COPYING
FILE SYSTEM ENTRIES below) to copy directories and their file system
entries;
- SystemClock::time_point modification() const:
returns the SystemClock::time_point of the (existing) file system
entry represented by the calling object;
- FileSystem [const] &noEC() [const]:
if the calling object uses an EC, then the EC won't be used
anymore after calling this member;
- FileSystem parent() const:
returns a FileSystem object initialized with the parent Path of
the calling object. The parent is equal to the calling object's
Path from which its filename has been removed (returning an
empty object if the calling object merely contains `/');
- Path const &path() const:
returns the current object's Path data member. When inserting
path() into an ostream Path is surrounded by double
quotes. If that's not required call the string member;
- Perms permissions() const:
returns the permissions of the calling object, which must refer to an
existing file system entry. The returned Perms value consists of
bitwise or-ed values of the std::filesystem::perms enum class, but
can be statically cast to mode_t values which are used as argument
to chmod(2);
- Ranger<[Const]Iter> range() [const]:
returns a pair of iterators visiting all components of the calling
object's Path.Example:
for (auto const &comp: fs.range())
cout << comp << '\n';
- FileSystem relative() const:
returns a copy of the calling object from which an initial `/' has
been removed;
- bool remove() const:
returns true if the current object's file system entry has been
removed;
- size_t removeAll() const:
returns the number of (recursively) removed file system entries
starting at the calling object's Path. The calling object doesn't
have to specify a directory;
- bool rename(Type const &newName) const:
returns true if the current file system entry could be renamed to
newName. The calling object's Path is not altered;
- bool resize(std::uintmax_t size) const:
returns true if the current file system entry could be resized to
size;
- bool sameAs(Type const &other) const:
returns true if other refers to the same file system entry as
the calling object. It is called by operator== as its lhs
member;
- FileSystem &setCwd():
changes the current process's current working directory to the
directory specified by the calling object;
- static FileSystem setCwd(Path const &path [, EC &ec]):
this static member changes the current process's current working
directory to the directory specified by its Path argument;
- FileSystem &setExtension(std::string const &ext):
changes the filename extension of the current object to ext. A dot
(.) is used to separate the current object's stem (see below)
and the extension. The resulting file name only has a single dot;
- FileSystem &setFilename(std::string const &newName):
changes the current object's file name (including its extension) to
newName. If the current object refers to an existing file system
entry then that file system entry is kept as-is;
- bool setModification(FBB::DateTime const &time):
changes the modification time of the current file system entry to the
time time-specification;
- bool setModification(SystemClock::time_point const &time):
changes the modification time of the current file system entry to the
time time-specification;
- FileSystem [const] &setPermissions(PermType perms,
FSOptions opt = RESET) [const]:
changes the permissions of the current file system entry to perms,
which must be statically castable to Perms. Example:
// change "entry's" permissions to -rw-------
FileSystem{ "entry" }.setPermissions(0600);
- bool setType(FileType type, bool destination = true):
it's unclear what this function is used for. It calls
filesystem::(symlink_)status, using symlink_status when called
as type(false). It returns false if type doesn't match the
current file system entry referred, but the type itself isn't
modified;
- uintmax_t size() const:
returns the size in bytes of the current file system entry;
- FileStatus status(bool destination = true) const:
returns the filesystem::status of the current file system entry. If
the current object is a symlink and the symlink's status is requested
then call status(false);
- FileSystem stem() const:
returns the file name of the current object without its extension;
- std::string string() const:
returns the current object's Path data member as a std::string;
- static FileSystem tmpDir(Type arg [= true]):
this static member returns the file system's directory which is by
default used for temporary files. By default tmpDir uses
FileSystem::s_errorCode objct, when calling tmpDir(false) no
EC object is used;
- static FileSystem tmpDir(EC &ec):
this static member returns the file system's directory using the
specified EC object when determining the temporay directory;
- FileType type(bool destination = true) const:
returns the FileType of the current file system entry. If the
current object refers to a symlink call type(false) to receive the
symlink's type.
COPYING FILE SYSTEM ENTRIES
The member copy(Type const &dest, FSOptions cpOptions = DEFAULT)'s
first argument specifies the name of the copied file or directory. It's second
argument specifies the type of the copy-operation. Options can be combined
using binary operators (usually bit_or). The following combinations are
valid:
- FILE - unconditionally copies the current entry to dest;
- FILE | NEW - the current entry is copied to dest if dest
does not yet exist;
- FILE | REPLACE - the current entry is copied to dest if dest
already exists;
- FILE | UPDATE - the current entry is only copied to dest if it is
younger than dest;
- CP_SYMLINK - the current entry must be a symlink, dest may not
yet exist and becomes a symlink to the same destination as the
current entry's destination;
- NEW_LINK - dest may not yet exist. It becomes a hard-link to the
current entry. The current object must exist;
- NEW_SYMLINK - dest may not yet exist. It becomes a symlink to the
current entry. If the current entry is itself a symlink then dest
becomes a symlink to the current entry, and not to the entry the
current object refers to. The current object does not have to be an
existing file system entry;
- RECURSIVE - the current entry is recursively copied to dest. If
the current entry isn't a directory then the entry itself is copied as
if RECURSIVE was not specified;
- RECURSIVE | CP_SYMLINKS - like using RECURSIVE but existing
symlinks are copied as symlinks;
- RECURSIVE | ONLY_DIRS - like using RECURSIVE but only the
directory structure is copied;
- RECURSIVE | SKIP_SYMLINKS - like using RECURSIVE but existing
symlinks are not copied;
EXAMPLE
#include <iostream>
#include <string>
#include <exception>
#include <bobcat/filesystem>
using namespace std;
using namespace FBB;
int main(int argc, char **argv)
{
if (argc == 1)
{
cout << "1st arg: an existing file\n"
"2nd arg (optional): a directory owned by the caller\n";
return 1;
}
FileSystem fs{ argv[1] };
if (not fs.exists())
cout << "No such file " << argv[1] << '\n';
else
cout << "last modification date of " << argv[1] << ": " <<
fs.modification() << '\n';
cout << oct << "Permissions: 0" <<
static_cast<size_t>(fs.permissions()) << dec << '\n';
if (argc > 2)
{
cout << "Entries of " << argv[2] << ":\n";
FileSystem fs2{ argv[2] };
for (auto const &entry: fs2.dirRange())
cout << " " << entry << '\n';
cout << fs2.errorCode().message() << '\n';
}
}
FILES
bobcat/filesystem - defines the class interface
SEE ALSO
bobcat(7), chmod(2), datetime(3bobcat), ranger(3bobcat)
BUGS
None Reported.
BOBCAT PROJECT FILES
- https://fbb-git.gitlab.io/bobcat/: gitlab project page;
Debian Bobcat project files:
- libbobcat6: debian package containing the shared library, changelog
and copyright note;
- libbobcat-dev: debian package containing the
static library, headers, manual pages, and developer info;
BOBCAT
Bobcat is an acronym of `Brokken's Own Base Classes And Templates'.
COPYRIGHT
This is free software, distributed under the terms of the
GNU General Public License (GPL).
AUTHOR
Frank B. Brokken (f.b.brokken@rug.nl).