DIFF: list differences in source file

Description

Compares program source files, indicating lines that have been added or deleted. Does not correctly identify large numbers of inserts, line moves, or many other changes.

Categories

Compare & Search
Program Development
Program Maintenance

Related files

DIFF: Object file for utility.

User Instructions

DIFF compares two 80-character files and attempts to list differences between them, ignoring line numbers. The report produced by DIFF can be for all lines or just those lines that have changed. Several languages are supported, or the user can choose the columns to be compared.

If only changed lines are to shown, the report lists the line numbers from the first file in column 1, line numbers from the second in column 2, and the related text to the right. This report is located in the library #[uid]+DIFF, where [uid] is the user's initials.

Programmer Instructions

DIFF uses GETPARMS for all screens, so it can be run under program control.

DOC         Documentation screen; no data elements.  Press
            (RETURN) to continue.

OPTIONS     Enter data and press (RETURN) to continue.

  MODE      FILE        Set to LIB to compare files with
                        matching names in two libraries.

  REPLACE   NO          Set to YES to scratch listings from
                        previous DIFF sessions without
                        warning.

  LISTOPT   L           Listing option.  Set to 'L' to list
                        all lines or 'C' to list only changed
                        lines.

FORMAT      Enter data and press (RETURN) to continue.

  FORMAT    (blank)     Selects language to be processed.
                        Choose from (A)ssembler, (B)ASIC,
                        (C)OBOL, PL/(I), (R)PG, or 'X' for
                        other.

  LEFT      01          The columns to be compared.
  RIGHT     80          Works only with 'X' format choice
                        (above).

FILES       Enter data and press (RETURN) to continue.

  F1NAME    (blank)     The name and location of the "old"
  F1LIB     (blank)     file.
  F1VOL     (blank)

  F2NAME    (blank)     The name and location of the "new"
  F2LIB     (blank)     file.
  F2VOL     (blank)

  LISTNAME  (blank)     The name and location of the listing
  LISTLIB   #[uid]+DIFF file to be created.  If the file name
  LISTVOL   [spoolvol]  is left blank, the F2NAME will be
                        used.

EOJ         Press PF(01) to run again; (RETURN) to exit the
            program.

Example of use

DIFF's primary purpose is to show the differences between two copies of a source file. It might be used as a diagnostic tool in trying to explain program errors, or perhaps incorporated into software installation to record changes made. In conjunction with the COMPRLIB utility (which calls DIFF), it can help manage program development and maintenance activities.

Comments

DIFF works best with small changes and few differences between files. It is easily confused by large deletes and inserts, and does not properly recognize lines that have been moved (i.e. an implied delete and insert). The listings are somewhat difficult to read, since examples from both files are mixed.