The READU procedure reads unformatted binary data from a file into IDL variables. READU transfers data directly with no processing of any kind performed on the data.
READU, Unit, Var1, ..., Varn [, TRANSFER_COUNT=variable]
The IDL file unit from which input is taken.
Named variables to receive the data. For non-string variables, the number of bytes required for Var are read. When READU is used with a variable of type string, IDL reads exactly the number of bytes contained in the existing string. For example, to read a 5-character string, enter:
temp = '12345' READU, unit, temp
Set this keyword to a named variable in which to return the number of elements transferred by the input operation. Note that the number of elements is not the same as the number of bytes (except in the case where the data type being transferred is bytes). For example, transferring 256 floating-point numbers yields a transfer count of 256, not 1024 (the number of bytes transferred).
This keyword is useful with files opened with the RAWIO keyword to the OPEN routines. Normally, attempting to read more data than is available from a file causes the unfilled space to be zeroed and an error to be issued. This does not happen with files opened with the RAWIO keyword. Instead, the programmer must keep track of the transfer count.
The following keywords are obsolete:
For information on obsolete keywords, See Obsolete Features.
The following commands can be used to open the IDL distribution file people.dat and read an image from that file:
; Open the file for reading as file unit 1: OPENR, 1, FILEPATH('people.dat', SUBDIR = ['examples','data']) ; The image is a 192 by 192 byte array, so make B that size: B = BYTARR(192, 192) ; Read the data into B: READU, 1, B ; Close the file: CLOSE, 1 ; Display the image: TV, B
READ/READF, READS, WRITEU, Files and Input/Output, Unformatted Input/Output with Structures.