String Handles

Handles are the values that represent I/O in Idio. Obviously that means files and pipes and other traditional operating system I/O entities but also strings which is more unusual.

We can create input (to be read from) and output (to be written to) string handles which can subsequently be manipulated almost identically to regular I/O handles.

Having written to an output string handle we must call get-output-string to get the accumulated string back. You might compare with this having to run cat to retrieve the output you had written to a file.

input-string-handles.idio

;; normally the input string would not be static
ish := open-input-string "hello\nworld\n"

printf "line 1 is %s\n" (read-line ish)
printf "line 2 is %s\n" (read-line ish)

;; good housekeeping
close-handle ish

$ idio input-string-handles
line 1 is hello
line 2 is world

Let’s try reading from a regular file, writing it out to a string handle then printing the content of the string handle.

Warning

This assumes that output-string-handles.idio is in the current directory. Adjust as appropriate for your system.

Ordinary files are not searched for on IDIOLIB.

output-string-handles.idio

;; open ourselves -- inception!
fh := open-input-file "output-string-handles.idio"

;; create our destination string
osh := (open-output-string)

while #t {
  ln := handle-line fh
  line := read-line fh

  if (eof? fh) (break) {
    hprintf osh "line %2d: %s\n" ln line
  }
}

;; otherwise we waste a file descriptor
close-handle fh

printf "%s" (get-output-string osh)

;; osh would be garbage collected when it went out of scope
close-handle osh

$ idio output-string-handles
line  1: ;; open ourselves -- inception!
line  2: fh := open-input-file "output-string-handles.idio"
line  3:
line  4: ;; create our destination string
line  5: osh := (open-output-string)
line  6:
line  7: while #t {
line  8:   ln := handle-line fh
line  9:   line := read-line fh
line 10:
line 11:   if (eof? fh) (break) {
line 12:     hprintf osh "line %2d: %s\n" ln line
line 13:   }
line 14: }
line 15:
line 16: ;; otherwise we waste a file descriptor
line 17: close-handle fh
line 18:
line 19: printf "%s" (get-output-string osh)
line 20:
line 21: ;; osh would be garbage collected when it went out of scope
line 22: close-handle osh

Last built at 2024-05-21T06:11:41Z+0000 from 77077af (dev) for Idio 0.3