SPIFF 1 "February 2, 1988"

Table of contents


NAME

spiff - make controlled approximate comparisons between files

SYNOPSIS

spiff [ -s script ] [ -f sfile ] [ -bteviqcdwm ] [ -a \(br -r value ] -value file1 file2

DESCRIPTION

Spiff compares the contents of file1 and file2 and prints a description of the important differences between the files. White space is ignored except to separate other objects. Spiff maintains tolerances below which differences between two floating-point numbers are ignored. Differences in floating-point notation (such as 3.4 3.40 and 3.4e01) are treated as unimportant. User-specified delimited strings (i.e. comments) can also be ignored. Inside other user-specified delimited strings (i.e. quoted strings) whitespace can be significant.

Spiff's operation can be altered via command line options, a command script, and with commands that are embedded in the input files.

The following options affect spiff's overall operation.

-q
suppresses warning messages.
-v
use a visually oriented display. Works only in MGR windows.

Spiff has several flags to aid differencing of various programming languages. See EXAMPLES for a detailed description of the effects of these flags.
-C
treat the input files as C program source code.
-S
treat the input files as Bourne shell program source code.
-F
treat the input files as Fortran program source code.
-M
treat the input files as Modula-2 program source code.
-L
treat the input files as Lisp program source code.

By default, the output looks somewhat similar in appearance to the output of diff(1). Lines with differences are printed with the differences highlighted. If stdout is a terminal, as determined by isatty(), then highlighting uses standout mode as determined by termcap. If stdout is not a tty, then the underlining (via underscore/backspace/char) is used to highlight differences. The following option can control the format of the ouput.
-t
produce output in terms of individual tokens. This option is most useful for debugging as the output produced is verbose to the point of being unreadable.

The following option controls the differencing algorithm.
-e
compare each token in the files with the object in the same ordinal position in the other file. If the files have a different number of objects, a warning message is printed and the objects at the end of the longer file are ignored. By default, spiff uses a Miller/Myers algorithm to find a minimal edit sequence that will convert the contents of the first file into the second.
-<decimal-value>
sets a limit on the total number of insertions and deletions that will be considered. If the files differ by more than the stated amount, the program will give up, print a warning message, and exit.

The following options control the command script. More than one of each may appear at a time. The commands accumulate.
-f
a command script to be taken from file sfile
-s
causes the following argument to be taken as a command script.

The following options control how individual objects are compared.
-b
treat all objects (including floating-point numbers) as literals.
-c
ignore differences between upper and lower case.

The following commands will control how the files are parsed.
-w
treat white space as objects. Each white space character will be treated as a separate object when the program is comparing the files.
-m
treat leading sign characters ( + and - ) as separate even if they are followed by floating-point numbers.
-d
treat integer decimal numbers (such as 1987) as real numbers (subject to tolerances) rather than as literal strings.

The following three flags are used to set the default tolerances. The floating-point-numbers may be given in the formats accepted by atof(3).
-a
specifies an absolute value for the tolerance in floating-point numbers. The flag -a1e-2 will cause all differences greater than 0.01 to be reported.
-r
specifies a relative tolerance. The value given is interpreted as a fraction of the larger (in absolute terms) of the two floating-point numbers being compared. Thus, the flag -r0.1 will cause the two floating-point numbers 1.0 and 0.9 to be deemed within tolerance. The numbers 1.0 and 0.89 will be outside the tolerance.
-i
causes differences between floating-point numbers to be ignored.

If more than one -a, or -i flag appear on the command line, the tolerances will be OR'd together (i.e. any difference that is within any of the tolerances will be ignored).

If no default tolerances is set on the command line, the program will use a default tolerance of '-a


SCRIPT COMMANDS

A script consists of commands, one per line. Each command consists of a keyword possibly followed by arguments. Arguments are separated by one or more tabs or spaces. The commands are:

literal BEGIN-STRING [END-STRING [ESCAPE-STRING]]
Specifies the delimiters surrounding text that is to be treated as a single literal object. If only one argument is present, then only that string itself is treated as a literal. If only two arguments are present, they are taking as the starting and ending delimiters respectively. If three arguments are present, they are treated as the start delimiter, end delimiter, and a string that may be used to escape an instance of the end delimiter.
beginchar BEGINNING-OF-LINE-CHARACTER
Set the beginning of line character for BEGIN-STRING's in comments. The default is `^'.
endchar END-OF-LINE-CHARACTER
Set the end of line character for END-STRING's in comments. The default is `$'.
addalpha NEW-ALPHA-CHARACTER
Add NEW-ALPHA-CHARACTER to the set of characters allowed in literal strings. By default, spiff parses sequences of characters that begin with a letter and followed by zero or more letters or numbers as a single literal token. This definition is overly restrictive when dealing with programming languages. For example, in the C programming language, the underscore character is allowed in identifiers.
comment BEGIN-STRING [END-STRING [ESCAPE-STRING]]
Specifies the delimiters surrounding text that is to be ignored entirely (i.e. viewed as comments). The operation of the comment command is very similar to the literal command. In addition, if the END-STRING consists of only the end of line character, the end of line will delimit the end of the comment. Also, if the BEGIN-STRING starts with the beginning of line character, only lines that begin with the BEGIN-STRING will be ignored.

More than one comment specification and more than one literal string specification may be specified at a time.
nestcom BEGIN-STRING [END-STRING [ESCAPE-STRING]]
Similar to the comment command, but allows comments to be nested. Note, due to the design of the parser nested comments can not have a BEGIN-STRING that starts with the beginning of line character.
resetcomments
Clears the list of comment specifications.
resetliterals
Clears the list of literal specifications.
tol [aVALUE\(brrVALUE\(bri\(brd . . . [ ; aVALUE\(brrVALUE\(bri\(brd . . . ] . . . ]
set the tolerance for floating-point comparisons. The arguments to the tol command are a set of tolerance specifications separated by semicolons. If more than one a,r,d, or i appears within a specification, then the tolerances are OR'd together (i.e. any difference that is within any tolerance will be ignored). The semantics of a,r, and i are identical to the -a, and -i flags. The d means that the default tolerance (as specified by the invocation options) should be used. If more than one specification appears on the line, the first specification is applied to the first floating-point number on each line, the second specification to the second floating-point number one each line of the input files, and so on. If there are more floating-point numbers on a given line of input than tolerance specifications, the last specification is used repeatedly for all remaining floating-point numbers on that line.
command STRING
lines in the input file that start with STRING will be interpreted as command lines. If no "command" is given as part of a -s or -f then it will be impossible to embed commands in the input files.
rem
#
used to place human readable remarks into a command script. Note that the use of the `#' character differs from other command languages (for instance the Bourne shell). Spiff will only recognize the `#' as beginning a comment when it is the first non-blank character on the command line. A `#' character appearing elsewhere will be treated as part of the command. Cautious users should use `rem'. Those hopelessly addicted to `#' as a comment character can have command scripts with a familiar format.

Tolerances specified in the command scripts have precedence over the tolerance specified on the invocation command line. The tolerance specified in file1 has precedence over the tolerance specified in file2.


VISUAL MODE

If spiff is invoked with the -v option, it will enter an interactive mode rather than produce an edit sequence. Three windows will be put on the screen. Two windows will contain corresponding segments of the input files. Objects that appear in both segments will be examined for differences and if any difference is found, the objects will be highlighted in reverse video on the screen. Objects that appear in only one window will have a line drawn through them to indicate that they aren't being compared with anything in the other text window. The third window is a command window. The command window will accept a single tolerance specification (followed by a newline) in a form suitable to the tol command. The tolerance specified will then be used as the default tolerance and the display will be updated to highlight only those objects that exceed the new default tolerance. Typing m (followed by a newline) will display the next screenful of text. Typing q (followed by a newline) will cause the program to exit.

LIMITS

Each input file can be no longer that 10,000 lines long or contain more than 50,000 tokens. Longer files will be truncated. No line can be longer than 1024 characters. Newlines will be inserted every 1024 characters.

EXAMPLES

spiff -e -d foo bar
this invocation (using exact match algorithm and treating integer numbers as if they were floats) is very useful for examining large tables of numbers.
spiff -0 foo bar
compare the two files, quitting after the first difference is found. This makes the program operate roughly like cmp(1).
spiff -0 -q foo bar
same as the above, but no output is produced. The return code is still useful.
spiff -w -b foo bar
will make the program operate much like diff(1).
spiff -a1e-5 -r0.001 foo bar
compare the contents of the files foo and bar and ignore all differences between floating-point numbers that are less than or equal to 0.00001 or 0.1% of the number of larger magnitude.
tol a.01 r.01
will cause all differences between floating-point numbers that are less than or equal to 0.01 or 1% of the number of larger magnitude to be ignored.
tol a.01 r.01 ; i
will cause the tolerance in the previous example to be applied to the first floating-point number on each line. All differences between the second and subsequent floating-point numbers on each line will be ignored.
tol a.01 r.01 ; i ; a.0001
like the above except that only differences between the second floating-point number on each line will be ignored. The differences between third and subsequent floating-point numbers on each number will be ignored if they are less than or equal to 0.0001.

A useful script for examing C code is:

literal  "    "    \
comment  /*  */
literal  &&
literal  \(br\(br
literal  <=
literal  >=
literal  !=
literal  ==
literal  --
literal  ++
literal  <<
literal  >>
literal  ->
addalpha _
tol      a0

A useful script for shell programs is:

literal  '    '    \
comment  #    $
tol      a0

A useful script for Fortran programs is:

literal ' ' '
comment ^C $
tol     a0

A useful script for Modula 2 programs is:

literal ' '
literal " "
nestcom (* *)
literal :=
literal <>
literal <=
literal >=
tol     a0

A useful script for Lisp programs is:

literal " "
comment ; $
tol     a0

DIAGNOSTICS

Spiff's exit status is 0 if no differences are found, 1 if differences are found, and 2 upon error.

BUGS

In C code, escaped newlines will appear as differences.

Comments are treated as token delimiters.

Comments in Basic don't work right. The line number is not ignored.

Continuation lines in Fortran comments don't work.

There is no way to represent strings specified using a Hollerith notation in Fortran.

In formatted English text, hyphenated words, movements in pictures, footnotes, etc. will be reported as differences.

STRING's in script commands can not include whitespace.

Visual mode does not handle tabs properly. Files containing tabs should be run through expand(1) before trying to display them with visual mode.

In visual mode, the text windows appear in a fixed size and font. Lines longer than the window size will not be handled properly.

Objects (literal strings) that contain newlines cause trouble in several places in visual mode.

Visual mode should accept more than one tolerance specification.

When using visual mode or the exact match comparison algorithm, the program should do the parsing on the fly rather than truncating long files.


AUTHOR

Daniel Nachbar

COPYRIGHT

                 Copyright (c) 1988 Bellcore
                     All Rights Reserved
Permission is granted to copy or use this program,
EXCEPT that it may not be sold for profit, the copyright
notice must be reproduced on copies, and credit should
be given to Bellcore where it is due.
         BELLCORE MAKES NO WARRANTY AND ACCEPTS
            NO LIABILITY FOR THIS PROGRAM.


SEE ALSO

atof(3) isatty(2) diff(1) cmp(1) expand(1) mgr(1L)

"Spiff -- A Program for Making Controlled Approximate Comparisons of Files", by Daniel Nachbar.

"A File Comparison Program" by Webb Miller and Eugene W. Myers in Software - Practice and Experience, Volume 15(11), pp.1025-1040, (November 1985).