WRITESEQF

    WRITESEQF expression { ON | TO } file.variable [ ON ERROR statements ]  \
              { THEN statements [ ELSE statements ] | ELSE statements }

The sequential file must be open, and the end-of-file marker must be reached before you can write to the file. You can use the FILEINFO function to determine the number of the line about to be written.

Normally, when you write a record using the WRITESEQ statement, the record is moved to a buffer that is periodically written to disk. If a system failure occurs, you could lose all the updated records in the buffer. The WRITESEQF statement forces the buffer contents to be written to disk; the program does not execute the statement following the WRITESEQF statement until the buffer is successfully written to disk.

A WRITESEQF statement following several WRITESEQ statements ensures that all buffered records are written to disk. WRITESEQF is intended for logging applications and should not be used for general programming. It increases the disk I/O of your program and therefore degrades performance. file.variable specifies a file opened for sequential access.

The value of expression is written to the file as the next line, and the THEN statements are executed. If THEN statements are not specified, program execution continues with the next statement; if the specified file cannot be accessed or does not exist, the ELSE statements are executed; any THEN statements are ignored.

If expression or file.variable evaluates to the null value, the WRITESEQF statement fails and the program terminates with a run-time error message.

The ON ERROR Clause

The ON ERROR clause is optional in the WRITESEQF statement. Its syntax is the same as that of the ELSE clause. The ON ERROR clause lets you specify an alternative for program termination when a fatal error is encountered while the WRITESEQF statement is being processed.