Comparing two sequential Files

[nikos]

What is the best possible way to compare two sequential files in a COBOL program? I'm trying to create one file that contains matched data, and one file that contains items that did not match. Can anyone provide me with some pseudocode?

 

[GeorgiK]

Hi,<br><br>It is not so easy to do comparing of two files.<br>First check your operating system utilities, for example:<br>for MS DOS/Windows use: FC file1 file2<br>for CompaqVMS use: Difference file1 file2<br>...<br>These utilities work intelligently, e.g. they don't match<br>each *pair* of records (one from file1 and one from file2)<br>but jump thru records which are &quot;non-comparable&quot; from<br>one file with records from another ... (it is very good<br>for comparing text files). There are also many switches<br>provided with them (especially for Diff for VAX/Alpha<br>VMS computers)<br>If you have to do comparing in your COBOL program,<br>try to read files alternatively:<br><br>&nbsp;&nbsp;OPEN INPUT FILE1 FILE2. (output file3)<br><br>&nbsp;&nbsp;MOVE 0 TO END1 END2.<br><br>PERFORM COMPARE-IT UNTIL END1 = 1 OR END2 = 1.<br><br>THE-END.<br>&nbsp;&nbsp;CLOSE FILE1 FILE2. (file3)<br>&nbsp;&nbsp;STOP RUN.<br><br>COMPARE-IT.<br>&nbsp;&nbsp;READ FILE1 AT END MOVE 1 TO END1.<br>&nbsp;&nbsp;READ FILE2 AT END MOVE 1 TO END2.<br>&nbsp;&nbsp;IF RECORD-1 NOT = RECORD-2<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;DISPLAY &quot;*** file1: ***&quot;<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;DISPLAY RECORD-1.<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;DISPLAY &quot;-------------------------&quot;<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;DISPLAY &quot;*** file2: ***&quot;<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;DISPLAY RECORD-2.<br>(YOU CAN ALSO USE WRITE RECORD-3 to file-3 if you want the differencies<br>written in a separate file)<br><br>note that this is simple checking. If your files are formatted it could work.<br>The real thing is to ignore or not to ignore &quot;white space&quot; (repetitive blanks,<br>tabs etc), to ignore upper and lower case etc.<br><br>Georgi, ;-)

 

[amosgreg]

Another way would be if the files are keyed,<br>(Psudo Code)<br>Sort both files on the same key<br>read 1 record from both files (Prime Read)<br>&nbsp;&nbsp;&nbsp;Move each record to a single working storage area of the length of the record&nbsp;&nbsp;File-1-rec and&nbsp;&nbsp;File-2-rec&nbsp;&nbsp;<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(Also define the Key File-1-rec-key) <br><br>Set up Loop<br><br>Evaluate True<br><br>&nbsp;&nbsp;&nbsp;When File 1 End of File<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;write file 2 until End of File<br>&nbsp;&nbsp;&nbsp;When File 2 End of File&nbsp;&nbsp;<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;write file 2 until End of File<br><br>&nbsp;&nbsp;&nbsp;When File-1-rec-key = File-2-rec-key&nbsp;&nbsp;<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;If File-1-rec = File-2-rec&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;write record same file<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;else write differance file&nbsp;&nbsp;with both records or the record of choice<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;end-if<br><br>&nbsp;&nbsp;&nbsp;When file-1-rec-key &gt; File-2-rec-key<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;write differance file&nbsp;&nbsp;with both records or the record of choice<br><br>&nbsp;&nbsp;&nbsp;When file-1-rec-key &lt; File-2-rec-key<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;write differance file&nbsp;&nbsp;with both records or the record of choice<br>&nbsp;&nbsp;&nbsp;&nbsp;<br>&nbsp;&nbsp;&nbsp;End-Evaluate<br><br><br><br>This code works very well and effeciently ( I bult a file compare just this way. 450 byte file structure and the whole compare code with comments was 26 lines.<br><br>remember the Evaluate criteria that it executes only the first condition that is satisfied, which is why the EOF check are first.<br><br>Hope this helps<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Greg&nbsp;&nbsp;<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<br>&nbsp;&nbsp;&nbsp;<br><br><br> <p>Greg Amos<br><a href=mailto:amosgreg@ix(dot)netcom(dot)com replace(dot)>amosgreg@ix(dot)netcom(dot)com replace(dot)</a><br><a href= > </a><br>