11.6.1.2485
WRITE-LINE
 
FILE
 
( c-addr u fileid -- ior )

Write u characters from c-addr followed by the implementation-dependent line terminator to the file identified by fileid starting at its current position. ior is the implementation-defined I/O result code.

At the conclusion of the operation, FILE-POSITION returns the next file position after the last character written to the file, and FILE-SIZE returns a value greater than or equal to the value returned by FILE-POSITION.

Testing:
: line1 S" Line 1" ;

T{ fn1 W/O OPEN-FILE SWAP fid1 ! -> 0 }T
T{ line1 fid1 @ WRITE-LINE -> 0 }T
T{ fid1 @ CLOSE-FILE -> 0 }T