isCOBOL Evolve : Appendices : Library Routines : CBL_READ_FILE
CBL_READ_FILE
The CBL_READ_FILE library routine reads bytes from a file.
Syntax:
 CALL "CBL_READ_FILE" USING fileHandle
                            offset
                            byteCount
                            flags
                            buffer
                     GIVING returnCode
Parameters:
fileHandle
PIC X(4) COMP-X
A handle returned from CBL_OPEN_FILE.
offset
PIC X(8) COMP-X
The offset in the file at which to read. This field is limited to a maximum value of 4294967295 unless accessMode is set to 64 when the file is opened using CBL_OPEN_FILE or CBL_CREATE_FILE.
byteCount
PIC X(4) COMP-X
Specifies the number of bytes to read.
flags
PIC X COMP-X
Possible values are:
0... Returns read content in the buffer field
128... Returns the file size in the offset field
buffer
PIC X(n)
Receives the read bytes .
Return code:
returnCode can be any numeric data item and provides additional information:
0
Operation successful.
>0
Error status.
Examples:
Example - Read the first three bytes of an opened file
working-storage section.
...
01 file-handle pic x(4) comp-x.
01 ofs         pic x(8) comp-x.
01 cnt         pic x(4) comp-x.
01 flg         pic x comp-x value 0.
01 buff        pic x(3).
...
procedure division.
... 
move 1 to ofs.
move 3 to cnt.
call "cbl_read_file" using file-handle, ofs,
                           cnt, flg, buff.