INPUT (file mode) - mkilgore/QB64pe GitHub Wiki

The OPEN statement is used to open a file or COM serial communications port for program input or output.

OPEN fileName$ [FOR] [{ACCESS|{LOCK|SHARED}}][{READ|WRITE}] AS [#]fileNumber& [LEN]

OPEN modeLetter$, [#]fileNumber&, fileName$[,]

• The fileName$ is a STRING variable or literal file name (path optional) in quotes.
• FOR mode can be: APPEND (write to end), BINARY (read/write), INPUT (read), OUTPUT (write new) or RANDOM (read/write).
• GW-BASIC's modeLetter$ is a STRING variable or the letter "A", "B", "I", "O" or "R" designating the OPEN modes above.
• fileNumber& can be any positive INTEGER or LONG whole number value or an unused value determined by the FREEFILE function.
• LEN = or recordLength is optional to denote the RANDOM file record byte length (default = 128) or sequential (default = 512) load buffer.

• QB64 can open as many files as your computer memory can handle. QBasic could only open about 15 at a time.
• QB64 will allocate 4 bytes of memory for every possible file number up to the highest number used in a program.
• mode defaults to RANDOM if the mode or FOR access statement is omitted. (see open modes described below)
• Only the fileName$, fileNumber& and LEN = recordLength values can use variable values in the QBasic syntax.
• If LEN = is ommitted, sequential file record sizes default to 512 and RANDOM to 128 bytes in Qbasic.
• fileName$ can be up to 255 characters with no limit on file name extension length in QB64.
• Once a file or port is opened, it can be used in any program procedure using the assigned file number.
• The "SCRN:" device is supported in version 1.000 and up (see Example 3).
• Devices such as "KYBD:", "CONS:", "COMn" and "LPTn:" are not supported in QB64..

Note: OPEN "LPTn" is not supported by QB64, but may be supported directly by your operating system.

• OPEN COM can also be used for serial port access in QB64.

• Illegal QB64 Windows filename characters are " * / \ | ? : < > . Multiple dots (periods) are allowed.
• Possible OPEN errors include "Bad file name or number", "Bad File Mode", "File Not Found" or "Path Not Found".
  • An OPEN file not found error may occur if CHR$(0) to (31) are used in a Windows file name.
• QB64 does not have DOS file name limitations.

• ACCESS clause limits file access to READ, WRITE or READ WRITE on a network.
• LOCK clause can specify SHARED or a LOCK READ or LOCK WRITE file lock in an OPEN statement working on a network.
• A separate LOCK statement can lock or UNLOCK file access on a network using a format that can lock specific records.
• If another process already has access to a specified file, program access is denied for that file OPEN access. A "Permission Denied" error 70 will be returned. A network program must be able to handle a denial of access error.

• FOR mode can be:
  • OUTPUT: Sequential mode creates a new file or erases an existing file for new program output. Use WRITE # to write numerical or text data or PRINT # for text. OUTPUT clears files of all data and clears the receive buffer on other devices such as COM.
  • APPEND: Sequential mode creates a new file if it doesn't exist or appends program output to the end of an existing file. Use WRITE # for numerical or text data or PRINT # for text as in the OUTPUT mode. APPEND does not remove previous data.
  • INPUT : Sequential mode only reads input from an existing file. File error if file does not exist. Use INPUT # for comma separated numerical or text data and LINE INPUT # or INPUT$ to only read text data. Use _FILEEXISTS or _DIREXISTS to avoid errors.
  • BINARY: Creates a new file when it doesn't exist or reads and writes to an existing binary file. Use GET # to read or PUT # to write byte positions simultaneously. LEN = statements are ignored in this mode.
  • RANDOM: Creates a new file when it doesn't exist or reads or writes to an existing random file record. Use GET # or PUT # to read or write to file records. A LEN = statement can define the byte size of a record (no LEN statement defaults to 128 bytes)
  • Modes INPUT, BINARY and RANDOM allow a file to be concurrently opened in a different mode and number.

• Mode letter is a variable or literal STRING letter value as one of the following:
  • "A" = APPEND.
  • "B" = BINARY.
  • "I" = INPUT.
  • "O" = OUTPUT.
  • "R" = RANDOM.

Example 1: Function that displays errors and the number of errors in QBasic filenames. Returns 0 when filename is OK.

FUNCTION CheckName% (Filename$)
  'NOTE: Function also displays filename errors so LOCATE on screen before call!
  DIM L AS INTEGER, DP AS INTEGER, XL AS INTEGER
  L = LEN(Filename$): DP = INSTR(Filename$, "."): IF...THEN DP THEN XL = L - DP 'extension
  IF...THEN L = 0 OR (boolean) L > 12 OR (boolean) DP > 9 OR (boolean) XL > 3 THEN 
    CheckName% = -1: COLOR 12: PRINT "Illegal format!"&#59; : EXIT FUNCTION
  END IF
  FOR...NEXT i% = 1 TO L      'check each filename character"
     code% = ASC(MID$(Filename$, i%, 1)): COLOR 10      ' see ASCII codes
     SELECT CASE code%       'check for errors and highlight in red
	'CASE 34, 42 TO 44, 47, 58 TO 63, 91 TO 93, 124: E% = E% + 1: COLOR 12 ' '''QBasic errors'''
        CASE 34, 42, 47, 58, 60, 62, 92, 124: E% = E% + 1: COLOR 12 ' '''QB64 errors'''
        CASE 46: dot% = dot% + 1: IF...THEN dot% > 1 THEN E% = E% + 1: COLOR 12
     END SELECT     
     PRINT CHR$(code%)&#59;  'use LOCATE before FUNCTION call to place print
  NEXT  
  CheckName% = E%
END FUNCTION '' ''

                         <span style="color:#54FC54&#59;">Hello</span><span style="color:red&#59;">,</span><span style="color:#54FC54&#59;">~1.mp3</span>  <span style="color:yellow&#59;">Total Errors</span> = <span style="color:yellow&#59;">1</span>

Note: The screen output displays filename characters in green except for red comma QBasic error.

FOR...NEXT i = 1 TO 2
    PRINT (file statement) #i, "Hello World, Screen and File version"
NEXT '' ''

Note: Linux or Mac file names can use a path destination such as ".\SCRN:" to use SCRN: as an actual file name.

OPEN "test.tst" FOR (file statement) OUTPUT AS #1
PRINT (file statement) #1, "If test.tst didn't exist:"
PRINT (file statement) #1, "A new file was created named test.tst and then deleted."
PRINT (file statement) #1, "If test.tst did exist:"
PRINT (file statement) #1, "It was overwritten with this and deleted."
CLOSE #1

OPEN "test.tst" FOR (file statement) INPUT (file mode) AS #1
DO UNTIL EOF(1)
INPUT (file statement) #1, a$
PRINT a$
LOOP
CLOSE #1

KILL "test.tst"

END

If test.tst didn't exist:
A new file was created named test.tst and then deleted.
If test.tst did exist:
It was overwritten with this and deleted.

Warning: Make sure you don't have a file named test.tst before you run this or it will be overwritten.

• PRINT (file statement), INPUT (file statement)
• GET, PUT, WRITE (file statement)
• INPUT$, LINE INPUT (file statement)
• CLOSE, LOF, EOF, LOC
• SEEK (statement), SEEK
• OPEN COM, LEN, RESET
• FIELD, TYPE
• _FILEEXISTS, _DIREXISTS
• _OPENCLIENT, _OPENHOST, _OPENCONNECTION (TCP/IP)
• _SNDOPEN, _LOADIMAGE