Native File Read R←⎕NREAD Y

This monadic function reads data from a native file. Y is a 3- or 4-element integer vector whose elements are as follows:

`[1]`	negative tie number,
`[2]`	conversion code (see below),
`[3]`	count. If this value is `¯1` , all of the elements defined by `Y[2]` are read from the position specified by `Y[4]` to the end of the file. This may result in the last few bytes in the file being ignored if they do not form a complete element.
`[4]`	start byte, counting from 0. If this value omitted or is `¯1` , data is read starting from the current position in the file (initially `0` ).

Notes

8 ⎕NINFO ⊃Y can be used to report the current position of the file pointer.

Y[2] specifies conversion to an APL internal form as follows. Note that the internal formats for character arrays differ between the Unicode and Classic Editions.

If both Y[3] and Y[4] have the value ¯1, then ⎕NREAD reads data from the current position in the file to the end of the file.

⎕NREAD can be used with any file. However, calling ⎕NREAD with at least one of Y[3 4] set to ¯1 is intended for regular files only; using on pipes, FIFOs or other special types of file is not recommended.

Table 1: Unicode Edition: Conversion Codes
Value	Number of bytes read	Result Type	Result shape
11	count	1 bit Boolean	8 `×` count
80	count	8 bits character	count
82 ¹	count	8 bits character	count
83	count	8 bits integer	count
160	2 `×` count	16-bits character	count
163	2 `×` count	16 bits integer	count
320	4 `×` count	32-bits character	count
323	4 `×` count	32 bits integer	count
645	8 `×` count	64 bits floating	count
1287	16 `×` count	128 bits decimal	count
1289	16 `×` count	128 bits complex	count

Table 2: Classic Edition: Conversion Codes
Value	Number of bytes read	Result Type	Result shape
11	count	1 bit Boolean	8 `×` count
82	count	8 bits character	count
83	count	8 bits integer	count
163	2 `×` count	16 bits integer	count
323	4 `×` count	32 bits integer	count
645	8 `×` count	64 bits floating	count
1287	16 `×` count	128 bits decimal	count
1289	16 `×` count	128 bits complex	count

Example

      DATA←⎕NREAD ¯1 160 (0.5×⎕NSIZE ¯1) 0 ⍝ Unicode
      DATA←⎕NREAD ¯1 82 (⎕NSIZE ¯1) 0      ⍝ Classic
      DATA←⎕NREAD ¯1 82 ¯1 0       ⍝ Shorter version

Conversion code 82 is permitted in the Unicode Edition for compatibility and causes 1-byte data on file to be translated (according to ⎕NXLATE ) from ⎕AV indices into normal (Unicode) characters of type 80, 160 or 320. ↩