Close an open file descriptor
Int_Type close (FD_Type fd)
The close function is used to close an open file descriptor
created by the open function. Upon success 0 is returned,
otherwise the function returns -1 and sets errno accordingly.
Close an open file descriptor
Int_Type _close (Int_Type fd)
The _close function is used to close the underlying integer
open file descriptor. Upon success 0 is returned, otherwise the
function returns -1 and sets errno accordingly.
Duplicate a file descriptor
FD_Type dup_fd (FD_Type fd)
The dup_fd function duplicates a specified file descriptor and
returns the duplicate. If the function fails, NULL will be
returned and errno set accordingly.
This function is essentially a wrapper around the POSIX dup
function.
Duplicate a file descriptor
Int_Type dup2_fd (FD_Type fd, int newfd)
The dup2_fd function makes newfd a copy of the
specified file descriptor fd. Upon success returns newfd,
otherwise it returns -1 and sets errno accordingly.
Get the underlying integer file descriptor
Int_Type _fileno (File_Type|FD_Type fp)
The _fileno function returns the underlying integer
descriptor for a specified stdio File_Type or
FD_Type object. Upon failure it returns -1 and sets
errno accordingly.
Convert a stdio File_Type object to a FD_Type descriptor
FD_Type fileno (File_Type fp)
The fileno function returns the FD_Type descriptor
associated with the stdio File_Type file pointer. Upon failure,
NULL is returned.
Closing the resulting file descriptor will have no effect.
Determine if an open file descriptor refers to a terminal
Int_Type isatty (FD_Type or File_Type fd)
This function returns 1 if the file descriptor fd refers to a
terminal; otherwise it returns 0. The object fd may either
be a File_Type stdio descriptor or a lower-level FD_Type
object.
Reposition a file descriptor's file pointer
Long_Type lseek (FD_Type fd, LLong_Type ofs, int mode)
The lseek function repositions the file pointer associated
with the open file descriptor fd to the offset ofs
according to the mode parameter. Specifically, mode must be
one of the values:
SEEK_SET Set the offset to ofs from the beginning of the file
SEEK_CUR Add ofs to the current offset
SEEK_END Add ofs to the current file size
lseek returns -1 and sets errno. If
successful, it returns the new filepointer offset.
Not all file descriptors are capable of supporting the seek operation, e.g., a descriptor associated with a pipe.
By using SEEK_END with a positive value of the ofs
parameter, it is possible to position the file pointer beyond the
current size of the file.
Open a file
FD_Type open (String_Type filename, Int_Type flags [,Int_Type mode])
The open function attempts to open a file specified by the
filename parameter according to the flags parameter,
which must be one of the following values:
O_RDONLY (read-only)
O_WRONLY (write-only)
O_RDWR (read/write)
flags may also be bitwise-or'd with any of the
following:
O_BINARY (open the file in binary mode)
O_TEXT (open the file in text mode)
O_CREAT (create the file if it does not exist)
O_EXCL (fail if the file already exists)
O_NOCTTY (do not make the device the controlling terminal)
O_TRUNC (truncate the file if it exists)
O_APPEND (open the file in append mode)
O_NONBLOCK (open the file in non-blocking mode)
If O_CREAT is used for the flags parameter then the
mode parameter must be present. mode specifies the
permissions to use if a new file is created. The actual file
permissions will be affected by the process's umask via
mode&~umask. The mode parameter's value is
constructed via bitwise-or of the following values:
S_IRWXU (Owner has read/write/execute permission)
S_IRUSR (Owner has read permission)
S_IWUSR (Owner has write permission)
S_IXUSR (Owner has execute permission)
S_IRWXG (Group has read/write/execute permission)
S_IRGRP (Group has read permission)
S_IWGRP (Group has write permission)
S_IXGRP (Group has execute permission)
S_IRWXO (Others have read/write/execute permission)
S_IROTH (Others have read permission)
S_IWOTH (Others have write permission)
S_IXOTH (Others have execute permission)
open returns a file descriptor object
(FD_Type), otherwise NULL is returned and errno
is set.
If you are not familiar with the open system call, then it
is recommended that you use fopen instead and use the higher
level stdio interface.
Read from an open file descriptor
UInt_Type read (FD_Type fd, Ref_Type buf, UInt_Type num)
The read function attempts to read at most num bytes
into the variable indicated by buf from the open file
descriptor fd. It returns the number of bytes read, or -1
upon failure and sets errno. The number of bytes
read may be less than num, and will be zero if an attempt is
made to read past the end of the file.
read is a low-level function and may return -1 for a variety
of reasons. For example, if non-blocking I/O has been specified for
the open file descriptor and no data is available for reading then
the function will return -1 and set errno to EAGAIN.
Write to an open file descriptor
UInt_Type write (FD_Type fd, BString_Type buf)
The write function attempts to write the bytes specified by
the buf parameter to the open file descriptor fd. It
returns the number of bytes successfully written, or -1 and sets
errno upon failure. The number of bytes written may be less
than length(buf).