13.1.6 String Ports
A string port reads or writes from a byte string. An input string port can be created from either a byte string or a string; in the latter case, the string is effectively converted to a byte string using string->bytes/utf-8. An output string port collects output into a byte string, but get-output-string conveniently converts the accumulated bytes to a string.
Input and output string ports do not need to be explicitly closed. The file-position procedure works for string ports in position-setting mode.
Byte Strings also provides information on bytestrings.
procedure
(string-port? p) → boolean?
p : port?
Added in version 6.0.1.6 of package base.
procedure
(open-input-bytes bstr [name]) → (and/c input-port? string-port?)
bstr : bytes? name : any/c = 'string
> (define sp (open-input-bytes #"(apples 42 day)")) > (define sexp1 (read sp)) > (first sexp1) 'apples
> (rest sexp1) '(42 day)
> (read-line (open-input-bytes #"the cow jumped over the moon\nthe little dog\n")) "the cow jumped over the moon"
procedure
(open-input-string str [name]) → (and/c input-port? string-port?)
str : string? name : any/c = 'string
> (define sp (open-input-string "(λ (x) x)")) > (read sp) '(λ (x) x)
> (define names (open-input-string "Günter Harder\nFrédéric Paulin\n")) > (read-line names) "Günter Harder"
> (read-line names) "Frédéric Paulin"
procedure
(open-output-bytes [name]) → (and/c output-port? string-port?)
name : any/c = 'string
> (define op1 (open-output-bytes)) > (write '((1 2 3) ("Tom" "Dick") ('a 'b 'c)) op1) > (get-output-bytes op1) #"((1 2 3) (\"Tom\" \"Dick\") ((quote a) (quote b) (quote c)))"
> (define op2 (open-output-bytes)) > (write "Hi " op2) > (write "there" op2) > (get-output-bytes op2) #"\"Hi \"\"there\""
> (define op3 (open-output-bytes)) > (write-bytes #"Hi " op3) 3
> (write-bytes #"there" op3) 5
> (get-output-bytes op3) #"Hi there"
procedure
(open-output-string [name]) → (and/c output-port? string-port?)
name : any/c = 'string
> (define op1 (open-output-string)) > (write '((1 2 3) ("Tom" "Dick") ('a 'b 'c)) op1) > (get-output-string op1) "((1 2 3) (\"Tom\" \"Dick\") ((quote a) (quote b) (quote c)))"
> (define op2 (open-output-string)) > (write "Hi " op2) > (write "there" op2) > (get-output-string op2) "\"Hi \"\"there\""
> (define op3 (open-output-string)) > (write-string "Hi " op3) 3
> (write-string "there" op3) 5
> (get-output-string op3) "Hi there"
procedure
(get-output-bytes out [ reset? start-pos end-pos]) → bytes? out : (and/c output-port? string-port?) reset? : any/c = #f start-pos : exact-nonnegative-integer? = 0 end-pos : exact-nonnegative-integer? = #f
If reset? is true, then all bytes are removed from the port, and the port’s position is reset to 0; if reset? is #f, then all bytes remain in the port for further accumulation (so they are returned for later calls to get-output-bytes or get-output-string), and the port’s position is unchanged.
The start-pos and end-pos arguments specify the range of bytes in the port to return; supplying start-pos and end-pos is the same as using subbytes on the result of get-output-bytes, but supplying them to get-output-bytes can avoid an allocation. The end-pos argument can be #f, which corresponds to not passing a second argument to subbytes.
> (define op (open-output-bytes)) > (write '((1 2 3) ("Tom" "Dick") ('a 'b 'c)) op) > (get-output-bytes op) #"((1 2 3) (\"Tom\" \"Dick\") ((quote a) (quote b) (quote c)))"
> (get-output-bytes op #f 3 16) #" 2 3) (\"Tom\" "
> (get-output-bytes op #t) #"((1 2 3) (\"Tom\" \"Dick\") ((quote a) (quote b) (quote c)))"
> (get-output-bytes op) #""
procedure
(get-output-string out) → string?
out : (and/c output-port? string-port?)
> (define i (open-input-string "hello world")) > (define o (open-output-string)) > (write (read i) o) > (get-output-string o) "hello"