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File Error Information Several file system intrinsics are designed specifically for handling errors. If an I/O error occurs, most file system intrinsics return a condition code indicating this. Three intrinsics are used to determine the nature of the error, to return an error message, and to print a file information display. These are described in the following paragraphs. Returning file system error codes with FCHECK The FCHECK intrinsic returns an error code that indicates the nature of a file system I/O error. A table of error codes appears in the MPE/iX Intrinsics Reference Manual (32650-90028), or you can use FERRMSG (described below) to display an error message.
NOTE FCHECK cannot be used to determine a file system error number for a failed HPFOPEN call. Check the status parameter of HPFOPEN for this information.
FCHECK has five optional parameters. The filenum parameter indicates the file for which error information is to be returned. If you set this parameter to zero, FCHECK assumes that you want information about the last failed FOPEN call. The error code is returned in the errorcode parameter. Three other parameters give additional information about file system errors. The tlog parameter returns the number of halfwords read or written if an I/O error occurs. The blknum parameter gives the logical record count for a spoolfile or the physical record count for any other type of file. The numrecs parameter returns the number of logical records in the block where an error occurred. You must use the FCHECK intrinsic prior to calling FERRMSG, since the error code returned by FCHECK is used as a parameter in the call to FERRMSG. Returning error messages with FERRMSG The FERRMSG intrinsic is used following a call to FCHECK, to return an error message explaining the nature of a file system error. It has three required parameters: errorcode is the error number returned by FCHECK, msgbuf returns the error message, and msglgth returns the length of the error message returned in msgbuf. Example 2-11 demonstrates how to use FCHECK and FERRMSG to return an error message. This example shows a call to FCLOSE. If this returns a CCL condition, a call to FCHECK requests the error code; then FERRMSG returns the error message associated with this code: _________________________________________________ | | | | | | | FCLOSE(FILENUM,1,0); | | IF < | | THEN BEGIN | | FCHECK(FILENUM,ERRNUM); | | FERRMSG(ERRNUM,MESSAGE,LENGTH); | | PRINT(MESSAGE,-LENGTH,0); | | END; | | TERMINATE; | | | _________________________________________________ Example 2-11. Using FERRMSG to Return an Error Message If the FCHECK code has no assigned meaning, the following message appears: UNDEFINED ERROR errorcode Displaying file error information with PRINTFILEINFO The PRINTFILEINFO intrinsic (spelled PRINT'FILE'INFO for SPL users) prints a file information display on the job or session list device. The information shown depends upon whether or not a file was opened when the error occurred. The significance of the fields on these displays is explained in detail in the MPE/iX Intrinsics Reference Manual (32650-90028). For files not yet opened, or for which the FOPEN intrinsic failed, the display is shown in example 2-12. ______________________________________________________________ | | | | | +F-I-L-E---I-N-F-O-R-M-A-T-I-O-N---D-I-S-P-L-A-Y+ | | ! FILE NUMBER 5 IS UNDEFINED. ! | | ! ERROR NUMBER: 2 RESIDUE: 0 (WORDS) ! | | ! BLOCK NUMBER: 0 NUMREC: 0 ! | | +-----------------------------------------------+ | | | ______________________________________________________________ Example 2-12. File Information Display - Unopened File For files that were open when a CCG (EOF error) or CCL (irrecoverable file error) was returned, the file information display appears as shown in example 2-13. ______________________________________________________________ | | | | | +-F-I-L-E---I-N-F-O-R-M-A-T-I-O-N---D-I-S-P-L-A-Y+ | | ! FILE NAME IS TREEFILE.PSMG.LOZAR ! | | ! FOPTIONS: NEW,ASCII,FORMAL,F,NOCCTL,FEQ, ! | | ! NOLABEL ! | | ! AOPTIONS: INPUT,NOMR,NOLOCK,DEF,BUF,NOMULTI, ! | | ! WAIT,NOCOPY ! | | ! DEVICE TYPE: 0 DEVICE SUBTYPE: 9 ! | | ! LDEV: 2 DRT: 4 UNIT: 1 ! | | ! RECORD SIZE: 256 BLOCK SIZE: 256 (BYTES) ! | | ! EXTENT SIZE: 128 MAX EXTENTS: 8 ! | | ! RECPTR: 0 RECLIMIT: 1023 ! | | ! LOGCOUNT: 0 PHYSCOUNT: 0 ! | | ! EOF AT: 0 LABEL ADDR: %00201327630 ! | | ! FILE CODE: 0 ID IS PAULA ULABELS: 0 ! | | ! PHYSICAL STATUS: 1000000000000001 ! | | ! NUMBER WRITERS: 0 NUMBER READERS: 1 ! | | ! ERROR NUMBER: 0 RESIDUE: 0 ! | | ! BLOCK NUMBER: 0 NUMREC: 1 ! | | +------------------------------------------------+ | | | ______________________________________________________________ Example 2-13. File Information Display - Opened File Writing a file system error check procedure Error checking intrinsics can be used throughout a program every time there is an intrinsic call. Instead of repeating a call to PRINTFILEINFO many times, it is more efficient to write an error check procedure and call this procedure where necessary. Example 2-14 is a sample error check procedure, named FILERROR. This procedure is declared at the beginning of the program; from that point on, it can be called with a single statement. The procedure contains two parameters. FILENO is an identifier through which the file number is passed; PRINTFILEINFO then prints a file information display for that file. QUITNO is part of the abort message printed by the QUIT intrinsic. This enables you to determine the point at which the process was aborted. For more information, refer to the Process Management Programmer's Guide (32650-90023). ________________________________________________ | | | | | PROCEDURE FILERROR(FILENO,QUITNO); | | VALUE QUITNO; | | INTEGER FILENO,QUITNO; | | BEGIN | | PRINTFILEINFO(FILENO); | | QUIT(QUITNO); | | END; | | | ________________________________________________ example 2-14. Error Check Procedure Using PRINTFILEINFO