GET
The GET # statement reads data from a file or port device by bytes or record positions.
Syntax
- GET #fileNumber&, [position][, {targetVariable|targetArray()}]
Description
- fileNumber& is the file or port number used in the OPEN AS BINARY or RANDOM statement.
- The INTEGER or LONG byte position in a BINARY file or the record position in a RANDOM file must be greater than zero.
- The position can be omitted if the GET operations are consecutive based on the targetVariable TYPE byte size.
- The targetVariable type or FIELD variable size determines the byte size and the next position in the file.
- The first byte position in a file is 1.
- GET does not require a byte or record position or targetVariable (or comma) when using a FIELD statement.
- QB64 can PUT the entire contents of an array to a file and later GET those contents to a targetArray() (include brackets).
- GET may ignore the end of a file and return bad data. If the EOF function returns -1 after a GET operation, it indicates that the data has ended.
DO UNTIL EOF(1) GET #1, , value% IF NOT (EOF(1)) THEN PUT #2, , value% LOOP |
Availability
-
all -
all -
-
yes -
yes -
yes
- Since arrays in TYPEs were implemented in QB64-PE v4.5.0, this statement was adapted to properly handle it (see Example 3).
Examples
- Example 1
- Opening a RANDOM file using LEN to calculate and LEN = to designate the file record size.
TYPE variabletype x AS INTEGER ' '2 bytes y AS STRING * 12 ''12 bytes z AS LONG ' '4 bytes END TYPE ' '18 bytes total DIM record AS variabletype DIM newrec AS variabletype file$ = "testrand.inf" '<<<< filename may overwrite existing file number% = 1 '<<<<<<<<<< record number to write cannot be zero RecordLEN% = LEN(record) PRINT RecordLEN%; "bytes" record.x = 255 record.y = "Hello world!" record.z = 65535 PRINT record.x, record.y, record.z OPEN file$ FOR RANDOM AS #1 LEN = RecordLEN% PUT #1, number%, record 'change record position number to add records CLOSE #1 OPEN file$ FOR RANDOM AS #2 LEN = RecordLEN% NumRecords% = LOF(2) \ RecordLEN% PRINT NumRecords%; "records" GET #2, NumRecords%, newrec 'GET last record available CLOSE #2 PRINT newrec.x, newrec.y, newrec.z END |
18 bytes 255 Hello world! 65535 1 records 255 Hello world! 65535 |
Explanation The byte size of the record TYPE determines the LOF byte size of the file and can determine the number of records. To read the last record GET the number of records. To add a new record, use the number of records + 1 to PUT new record data. |
- Example 2
- Placing the contents of a numerical array into a BINARY file. You may want to put the array size at the beginning too.
DIM SHARED array(100) AS INTEGER FOR i = 1 TO 100 array(i) = i NEXT PrintArray 'display array contents OPEN "BINFILE.BIN" FOR BINARY AS #1 PUT #1, , array() ERASE array 'clear element values from array and display empty PrintArray CLOSE #1 OPEN "BINFILE.BIN" FOR BINARY AS #2 GET #2, , array() CLOSE #2 PrintArray 'display array after transfer from file END SUB PrintArray FOR i = 1 TO 100 PRINT array(i); NEXT PRINT "done" PRINT END SUB |
- Example 3
- Placing the contents of a nested numerical array into a BINARY file. You may want to put the array size at the beginning too.
TYPE test aaa(2) AS DOUBLE END TYPE DIM a(1) AS test PRINT "Generating values..." FOR y = 0 TO 1 FOR x = 0 TO 2 a(y).aaa(x) = (x + 1) * (y + 1) PRINT (x + 1) * (y + 1); NEXT x, y PRINT OPEN "s_test.dat" FOR BINARY AS #1 PRINT PRINT "Saving nested array content to file s_test.dat" PUT #1, , a() CLOSE #1 ERASE a 'delete content for a() and all nested arrays in a (see ERASE for more info) PRINT PRINT "Reading saved content..." OPEN "s_test.dat" FOR BINARY AS #1 GET #1, , a() CLOSE #1 FOR y = 0 TO 1 FOR x = 0 TO 2 PRINT a(y).aaa(x); NEXT x NEXT y |
See also