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27.9.2 String Ports

The following allow string ports to be opened by analogy to R4R* file port facilities:

call-with-output-string proc Scheme Procedure
scm_call_with_output_string (proc) C Function
Calls the one-argument procedure proc with a newly created output port. When the function returns, the string composed of the characters written into the port is returned.

call-with-input-string string proc Scheme Procedure
scm_call_with_input_string (string, proc) C Function
Calls the one-argument procedure proc with a newly created input port from which string's contents may be read. The value yielded by the proc is returned.

with-output-to-string thunk Scheme Procedure
Calls the zero-argument procedure thunk with the current output port set temporarily to a new string port. It returns a string composed of the characters written to the current output.

with-input-from-string string thunk Scheme Procedure
Calls the zero-argument procedure thunk with the current input port set temporarily to a string port opened on the specified string. The value yielded by thunk is returned.

open-input-string str Scheme Procedure
scm_open_input_string (str) C Function
Take a string and return an input port that delivers characters from the string. The port can be closed by close-input-port, though its storage will be reclaimed by the garbage collector if it becomes inaccessible.

open-output-string Scheme Procedure
scm_open_output_string () C Function
Return an output port that will accumulate characters for retrieval by get-output-string. The port can be closed by the procedure close-output-port, though its storage will be reclaimed by the garbage collector if it becomes inaccessible.

get-output-string port Scheme Procedure
scm_get_output_string (port) C Function
Given an output port created by open-output-string, return a string consisting of the characters that have been output to the port so far.

A string port can be used in many procedures which accept a port but which are not dependent on implementation details of fports. E.g., seeking and truncating will work on a string port, but trying to extract the file descriptor number will fail.