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Before Scheme can access a file for reading or writing, it is necessary
to open a port to the file. This section describes procedures used to
open ports to files. Such ports are closed (like any other port) by
close-port. File ports are automatically closed if and when they
are reclaimed by the garbage collector.
Before opening a file for input or output, by whatever method, the
filename argument is converted to canonical form by calling the
procedure merge-pathnames with filename as its sole
argument. Thus, filename can be either a string or a pathname,
and it is merged with the current pathname defaults to produce the
pathname that is then opened.
It is an error if procedure does not accept one argument.
These procedures obtain a textual port obtained by opening the named
file for input or output as if by open-input-file or
open-output-file. The port and procedure are then passed
to a procedure equivalent to call-with-port.
It is an error if procedure does not accept one argument.
These procedures obtain a binary port obtained by opening the named
file for input or output as if by open-binary-input-file or
open-binary-output-file. The port and procedure are then
passed to a procedure equivalent to call-with-port.
The file named by filename is opened for input or output as if
by open-input-file or open-output-file, and the new port
is made to be the value returned by current-input-port or
current-output-port (as used by (read), (write
obj), and so forth). The thunk is then called with no
arguments. When the thunk returns, the port is closed and the
previous default is restored. It is an error if thunk does not
accept zero arguments. Both procedures return the values yielded by
thunk. If an escape procedure is used to escape from the
continuation of these procedures, they behave exactly as if the
current input or output port had been bound dynamically with
parameterize.
These procedures are deprecated; instead use
parameterize along with call-with-binary-input-file or
call-with-binary-output-file.
Takes a filename for an existing file and returns a textual
input port or binary input port that is capable of delivering data
from the file. If the file does not exist or cannot be opened, an
error an error that satisfies file-error? is signaled.
Takes a filename naming an output file to be created and returns
a textual output port or binary output port that is capable of writing
data to a new file by that name. If a file with the given name
already exists, the effect is unspecified. (In that case, MIT/GNU
Scheme overwrites an existing file.) If the file cannot be opened, an
error that satisfies file-error? is signalled.
The optional argument append? is an MIT/GNU Scheme extension. If
append? is given and not #f, the file is opened in
append mode. In this mode, the contents of the file are not
overwritten; instead any characters written to the file are appended to
the end of the existing contents. If the file does not exist, append
mode creates the file and writes to it in the normal way.
Takes a filename referring to an existing file and returns an
I/O port that is capable of both reading from and writing to
the file. If the file cannot be opened, an error that satisfies
file-error? is signalled.
This procedure is often used to open special files. For example, under unix this procedure can be used to open terminal device files, PTY device files, and named pipes.
This procedure closes all file ports that are open at the time that it is called, and returns an unspecified value.
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