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(guile.info)File Ports

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File Ports
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The following procedures are used to open file ports.  See also Note:
open, for an interface to the Unix `open'
system call.

 - primitive: open-file filename modes
     Open the file whose name is STRING, and return a port representing
     that file.  The attributes of the port are determined by the MODE
     string.  The way in which this is interpreted is similar to C
     stdio:

     The first character must be one of the following:

    `r'
          Open an existing file for input.

    `w'
          Open a file for output, creating it if it doesn't already
          exist or removing its contents if it does.

    `a'
          Open a file for output, creating it if it doesn't already
          exist.  All writes to the port will go to the end of the file.
          The "append mode" can be turned off while the port is in use
          Note: fcntl.

     The following additional characters can be appended:

    `+'
          Open the port for both input and output.  E.g., `r+': open an
          existing file for both input and output.

    `0'
          Create an "unbuffered" port.  In this case input and output
          operations are passed directly to the underlying port
          implementation without additional buffering.  This is likely
          to slow down I/O operations.  The buffering mode can be
          changed while a port is in use Note: setvbuf.


    `l'
          Add line-buffering to the port.  The port output buffer will
          be automatically flushed whenever a newline character is
          written.

     In theory we could create read/write ports which were buffered in
     one direction only.  However this isn't included in the current
     interfaces.

     If a file cannot be opened with the access requested, `open-file'
     throws an exception.

 - procedure: open-input-file filename
     Open FILENAME for input.  Equivalent to
          (open-file FILENAME "r")

 - procedure: open-output-file filename
     Open FILENAME for output.  Equivalent to
          (open-file FILENAME "w")

 - primitive: port-mode port
     Returns the port modes associated with the open port PORT.  These
     will not necessarily be identical to the modes used when the port
     was opened, since modes such as "append" which are used only during
     port creation are not retained.

 - primitive: port-filename port
     Return the filename associated with PORT.  This function returns
     the strings "standard input", "standard output" and "standard
     error" when called on the current input, output and error ports
     respectively.

 - primitive: set-port-filename! port filename
     Change the filename associated with PORT, using the current input
     port if none is specified.  Note that this does not change the
     port's source of data, but only the value that is returned by
     `port-filename' and reported in diagnostic output.