User`s guide

DIFFERENCES
lists the differences on the terminal (or sends the differences to an output file if one
is specified). RT–11 then searches DU0 for more files with the file name PROG1 and
DU1 for PROG2 files with matching file types.
Some Uses of the DIFFERENCES Command
• Comparing two similar versions of a file
The DIFFERENCES command is useful when you want to compare two similar
versions of a source or binary program, typically an updated version against
a backup version. A file comparison listing highlights the changes made to a
program during an editing session.
• Creating command files to install patches
The DIFFERENCES command is also useful for creating command files that
can install patches to backup versions of programs so they match the updated
versions. The /SLP:filespec and /SIPP:filespec options are designed especially for
this purpose. The default file type for the output file created by /SLP is SLP,
while the default file type for the output file created by SIPP is COM. You cannot
use wildcards when creating SLP or SIPP command files.
Comparing Text Files
During a text comparison, RT–11 compares the two specified files, character for
character, and lists any lines that contain differences. By default, the listing is
displayed on the terminal screen. You can redirect the listing from the terminal to a
file by using the /OUTPUT:filespec option, or to the printer by using the /PRINTER
option.
Blank lines and the RETURN character are ignored; but all other characters, including
line feeds, tabs, and spaces are compared. By default, even differences between
uppercase and lowercase characters are listed.
If you compare two files that are identical, RT–11 does not create a listing but
displays the following message on the terminal screen:
?SRCCOM-I-No differences found
If you compare two files that are different, RT–11 produces a listing of the differences
and displays the following message on the terminal screen:
?SRCCOM-W-Files are different
If you use wildcards in the command line, RT–11 always displays the specifications
of the files being compared regardless of whether or not there are differences.
Two Example Files
To understand how to interpret the output listing, first look at the following
two sample FORTRAN text files: EXAMP.ONE and EXAMP.TWO. Notice the two
differences between the files:
• In line 7, the first file has go to 10, while the second file has go to 100.
78 RT–11 Command Descriptions