NV Exec README

AUTHOR

     Benjamin Cox


ABOUT

     NV Exec (N-Variant Executor) is a program designed to bring an
N-Variant System Framework into execution.  For more information on
the N-Variant System Framework itself refer to the following paper:
<http://www.cs.virginia.edu/~evans/pubs/nvariant/usenix06-packaged.pdf>


USAGE

     To invoke an N-Variant System framework using NV Exec, call NV
Exec with the command lines of the different variants separated by
"---".  For example:
    nvexec ENV=V1 ./v1_prog v1_arg --- ENV=V2 ./v2_prog v2_arg

     This command will invoke an N-Variant system with the first
variant executing v1_prog with the environment variable ENV=V1 and
v1_arg as its only argument.  The second variant will execute v2_prog
with the environment variable ENV=V2 and v2_arg as its only
argument.


COMPILING: 

 1.  Unpack the tarball:              #> tar -xzvf nvexec.tar.gz
 2.  Move into NV Exec's directory:   #> cd nvexec
 3.  Compile the program:             #> make


FAQs:

Q1: My binary has one or more equals ('=') characters as part of
    its name, how do I keep NV Exec from interpreting it as an
    environment variable?

A:  The easiest way to do this is to rename your binaries. If this
    isn't an option, just like executing the binary from the shell you
    will need to place a backslash "\" before each equals ('=')
    character.  NV Exec will see this and interpret it correctly.
    The shell from which you call NV Exec may remove a single '\'
    from the command line argument.  If this is the case (it is with
    /bin/sh) you'll need to put two backslashes before the equals sign
    to ensure the backslash is included in the arguments.  For
    example, to run the variants "prog.v=1" and "prog.v=2" you will
    need to type the following command into the shell:

      nvexec ENV=V1 ./prog.v\\=1 v1_arg --- ENV=V2 ./prog.v\\=2 v2_arg

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Q2: One or more of my variants require that it be passed "---" as an
    argument, what do I do to keep NV Exec from interpreting it as the
    delimiter between different variant command lines?

A:  You will need to modify the source code to do this.  Simply change
    the DELIMITER string found in nvexec.c to something that works
    for you.

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Q3: I don't want to recompile NV Exec each time I run into a conflict
    with the delimiter, what else can I do?

A:  Since this program is licensed under the GNU Public License you can
    easily modify the source code to dynamically set the delimiter.

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