isCOBOL Evolve : Appendices : Library Routines : S$IO
S$IO
The S$IO routine provides a low-level interface to sequential files allowing them to be managed without knowing their FD.
The configuration properties iscobol.file.linesequential and iscobol.file.linesequential.FileName specify which file handler is used for line sequential files.
The configuration properties iscobol.file.sequential and iscobol.file.sequential.FileName specify which file handler is used for binary sequential files.
Note - due to the use of external data items, this routine is not thread safe.
Syntax:
 CALL "S$IO" USING opCode 
                   parameters
            GIVING returnCode
Parameters:
opCode
Specifies the file handling function to be performed.
 
Valid values, defined in isfilesys.def are:
 
Opens an existing file
 
Closes an opened file
 
Creates an empty file
 
Reads a record from a file
 
Writes data into file
 
Rewrites data into file
parameters
Parameters depend on the opcode.
Return code:
returnCode contains useful information such as file handles and record sizes or zero if an error occurs. Check the external variable F_ERRNO for additional information on the error.
Examples:
Example - create a sequential file, write some records and then close it
       working-storage section.
       ...
       copy "isfilesys.def".
       77  f                       handle .
       77  file-io                 pic x(128).
 
 
       01  sio-lparms.
           03 max-rec-sz pic 9.
           03 filler     pic x value ",".
           03 file-type  signed-short.
           03 filler     pic x value ",".
           03 block-sz   pic 9 value 0.
 
       01  rec-buffer.
           03 rec-val    pic 9(5).
           03 filler     pic x value x"00".
       ...
       procedure division.
       ...
           set s-make-function to true
           call "s$io" using sio-function, 
                             file-io, 
                             sio-lparms
           if return-code = 0
              display message F_ERRNO 
                      icon    mb-error-icon
                      title   "S$IO Error: make" 
           end-if           
 
      *opening 
           display label line 4 title "Opening file..."
           set s-open-function to true
           move foutput to open-mode
           call "s$io" using sio-function, 
                             file-io, 
                             open-mode, 
                             max-rec-sz, 
                             seq-type, 
                             0, 
                             0  
 
           if return-code > 0
              move return-code to f
           else
              display message F_ERRNO 
                      icon    mb-error-icon
                      title   "S$IO Error: open" 
           end-if
 
      *record writing
           move 0 to rec-val.
           display label line 6 title "Writing into file..."  
           set s-write-function to true
           perform 5 times
              add 1 to rec-val
              call "s$io" using sio-function, 
                                f, 
                                rec-buffer, 
                                0, 
                                0
              if return-code = 0
                 display message F_ERRNO 
                         icon    mb-error-icon
                         title   "S$IO Error: write" 
              end-if
           end-perform
 
      *close file  
           display label line 8 title "Closing file..."
           set s-close-function to true.
           call "s$io" using sio-function, 
                             f.
 
           if return-code > 0
              move return-code to f
           else
              display message F_ERRNO 
                      icon    mb-error-icon
                      title   "S$IO Error: close" 
           end-if
...