This manual describes how to install and use Numdiff, a program which compares putatively similar files line by line and field by field, ignoring small numeric differences or/and different numeric formats.
Copyright (C) 2005, 2006 Ivano Primi ivprimi(at)libero(dot)it
Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2 or any later version published by the Free Software Foundation; with no Invariant Sections, with the Front-Cover Texts being "Numdiff User Manual, version 4.0", and with no Back-Cover Texts. A copy of the license is included in GNU Free Documentation License.
Numdiff (also written numdiff) is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version.
Numdiff is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
You should have received a copy of the GNU General Public License along with the program; if not, write to the Free Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA .
I want to thank Mr. Norman Clerman norm(dot)opcon(at)fuse(dot)net for several suggestions he gave me to improve the readability and the effectiveness of the output produced by Numdiff. Moreover, he pointed out the need to implement a filter to resynchronize the lines between two files in case of addition or deletion of one or more lines. I have to give him credit for the urge to prepare the version 4.0.0 of Numdiff.
Moreover, I want to thank my friend Mariapia Palombaro since she removed some errors while reviewing the first version of this document.
Computer users often find occasion to ask how two files differ. Perhaps one file is a newer version of the other file. Or maybe the two files started out as identical copies but were changed by different people.
There are several ways to think about the differences between two files. One way to think of the differences is as a series of lines that were deleted from, inserted in, or changed in one file to produce the other file. The well-known diff program compares two files line by line, finds groups of lines that differ, and reports each group of differing lines. Without particular options, the diff program considers any change in the amount or in the type of the characters as a relevant difference. However, trough some command line options it also provides ways to suppress certain kinds of differences that are not important to the user. For instance, diff provides ways to ignore differences in the amount of white space between words or lines, or differences in alphabetic case.
Another way to think of the differences is as a series of words that were deleted from, inserted in, or changed in one file to produce the other file. Here “word” refers to a sequence of non white-space characters delimited by a couple of white-spaces, one before and the other one after the word.
The less known wdiff program by Franc,ois Pinard <[email protected]> compares words in two files and reports the differences.
At last, one can think of the differences between two files as a sequence of pairs of bytes that can be either identical or different. The cmp program reports the differences between two files byte by byte, instead of line by line or word by word. As a result, it is often more useful than diff or wdiff for comparing binary files.
However, none of these approaches turns out to be good when you want to compare a couple of text files composed partially or entirely by numerical fields. Indeed, when you compare a couple of such files, what you want to obtain usually is a list of the numerical fields in the second file which numerically differ from the corresponding fields in the first file. But, as you probably knows, a same number can be written using different notations and programs like diff or wdiff can not recognize whether a difference between two numeric fields is only due to the notation or is actually a difference of numerical values.
For instance, 11.23 and 11.2300000 are the same number but represented in different ways. While, if you are interested in numerical values, it is obvious that the difference in the representation is not meaningful and then it should be ignored, however diff and wdiff consider the previous one as a relevant difference and there is no way for you to tell these programs to ignore it !
Another example of this type is given by 98765.4321 and 9.87654321E04 where the difference is only due to the use of the scientific notation in place of the common notation.
Moreover, depending on your country you could stick to different conventions in writing numbers. For instance, the amount “three hundred millions and fifty-two thousands of dollars and forty-six cents” is usually written by an Italian accountant as 300.052.000,46$ while an American accountant would write 300,052,000.46$. Of course, 300.052.000,46$ and 300,052,000.46$ represent the same amount of money but diff and wdiff would report a difference, which probably is not what you would in a similar case.
At last, sometimes you could want to ignore even differences in numerical values as long as they do not overcome a certain threshold. In other words, you could desire to suppress all “small” numerical differences too.
For instance, it could happen that you want to ignore all numerical differences whose absolute value is not greater than 0.0001. If this is the case, then the numerical fields 33 and 33.00009 must be considered equal, while 33 and 33.00011 must be reported as different.
However, diff and wdiff can not be used to ignore “small” numerical differences, since they do not even know what a numerical difference is.
What I have been saying till now explains why I decided to implement a new program with the capability to “appropriately” compare files containing numerical fields. In writing this program I was inspired by ndiff, a GPL'ed software by Nelson H. Baabe of the Salt Lake City University. The author of ndiff had the same good reasons as me to write ndiff. Actually ndiff is a good tool and I used it for a while. But I did not completely like the way it works and so numdiff was born. Although ndiff inspired numdiff, they are completely different from the viewpoint of the source code: numdiff has been entirely written from scratch.
numdiff can be used to compare putatively similar files line by line and field by field, ignoring small numeric differences or/and different numeric formats. numdiff takes two mandatory arguments, the paths of the two files to compare, and, after splitting them into lines and the lines into fields according to a given list of field delimiters, it compares every field of every line of the first file with the field of the second file at the same position (here position refers both to the line number and to the location within the line). If the compared fields are both legal numerical values, then numdiff performs a numerical comparison between them, else it performs a literal comparison, that is to say the usual byte by byte comparison. In case of literal comparison, two fields are regarded as equal if they are formed by the same sequence of characters. In case of numerical comparison and without specific command line options, two fields are regarded as equal if their numerical difference is zero. Be careful ! If you do not explicitly specify a list of field delimiters by the option -s, then numdiff takes as field delimiters the characters newline (`\n', ASCII code 0x0A), horizontal tabulation (`\t', ASCII code 0x09), and blank (` ', ASCII code 0x20).
For instance, if the file list1 contains the data
accident 123 23Joshua 34.55 +3+4i water dog -3455.321 cat 2.345678e-9 .0005-6.23e2iand file list2 contains the data
Accident 123 23456 34.5500 +3.0001+4i dog -3455.320098 Cat +2.345678e-9 -6.23e2i $$$ A new linethen the output of the command `numdiff list1 list2' will be:
----------------
##1 #:1 <== accident
==> Accident
@ @@
##1 #:3 <== 23Joshua
==> 23456
@ @@
##1 #:5 <== +3+4i
==> +3.0001+4i
@ Absolute error = 1.0000000000e-4, Relative error = 2.0000000000e-5
##1 #>6 <== water
==>
@ Line 1 in file "list2" is shorter!
----------------
##2 #:2 <== -3455.321
==> -3455.320098
@ Absolute error = 9.0200000000e-4, Relative error = 2.6104672633e-7
##2 #:3 <== cat
==> Cat
@ @@
##2 #:5 <== .0005-6.23e2i
==> -6.23e2i
@ Absolute error = 5.0000000000e-4, Relative error = 8.0256821830e-7
##2 #>6 <==
==> $$$
@ Line 2 in file "list1" is shorter!
----------------
##3 #>1 <==
==> A new line
@ Line 3 in file "list1" is shorter!
----------------
##4 <==
==>
+++ File "list1" differs from file "list2"
At the same time numdiff will print the following error message on stderr:
*** End of file "list1" reached
Likely the files "list1" and "list2" do not have the same number of lines !
I have to remark that numdiff can recognize complex numbers, provided that they are written in the form a+bi or a-bi with no extra characters between the values a, b and the sign + or - (actually the symbol i used to represent the imaginary unit can be changed by a suitable command line option, but we shall see it in Invoking). If you do not know what complex numbers are, do not worry ! In this case probably you will never manage files containing complex numbers and so you can happily continue to ignore them. :) Even if the output of numdiff is self-explanatory, in the next section I will explain in details all you have to know about it.
Let us go back to the previous example. If the files list1 and list2 contain the data
accident 123 23Joshua 34.55 +3+4i water dog -3455.321 cat 2.345678e-9 .0005-6.23e2iand
Accident 123 23456 34.5500 +3.0001+4i dog -3455.320098 Cat +2.345678e-9 -6.23e2i $$$ A new linerespectively, then the output of the command `numdiff list1 list2' will be:
----------------
##1 #:1 <== accident
==> Accident
@ @@
##1 #:3 <== 23Joshua
==> 23456
@ @@
##1 #:5 <== +3+4i
==> +3.0001+4i
@ Absolute error = 1.0000000000e-4, Relative error = 2.0000000000e-5
##1 #>6 <== water
==>
@ Line 1 in file "list2" is shorter!
----------------
##2 #:2 <== -3455.321
==> -3455.320098
@ Absolute error = 9.0200000000e-4, Relative error = 2.6104672633e-7
##2 #:3 <== cat
==> Cat
@ @@
##2 #:5 <== .0005-6.23e2i
==> -6.23e2i
@ Absolute error = 5.0000000000e-4, Relative error = 8.0256821830e-7
##2 #>6 <==
==> $$$
@ Line 2 in file "list1" is shorter!
----------------
##3 #>1 <==
==> A new line
@ Line 3 in file "list1" is shorter!
----------------
##4 <==
==>
+++ File "list1" differs from file "list2"
numdiff prints a report on the standard output for every field of the first file which differs from the corresponding field of the second one.
First this report indicates the location of the field, that is to say the number of the line where the field appears and its position within the line (this is “1” if it is the first field of its line, “2” if it is the second field of the line, “3” if it is the third one and so on. Fields are numerated starting from the left hand of the line and proceeding towards the right hand). For each report the line number is introduced by the symbol “##”, while the field number by “#:”. Then numdiff shows in what the difference consists. For instance,
##1 #:1 <== accident
==> Accident
@ @@
means that the first field of the first line is “accident” in the first file, while in the second file it appears as “Accident”. This difference could then be canceled by removing “accident” from the first file and inserting “Accident” in place of it. The arrows “<==” and “==>” try to visualize this idea. Analogously,
##2 #:2 <== -3455.321
==> -3455.320098
@ Absolute error = 9.0200000000e-4, Relative error = 2.6104672633e-7
means that the second field of the second line is “-3455.321” in the first file and “-3455.320098” in the second one. Since the contents of the field are numerical in both files, numdiff also prints the absolute and relative errors.
The absolute error (or absolute difference) is given by the absolute value of the difference between the values appearing in the two files.
The relative error (or relative difference) is actually defined in a more complicated way. If “n1” is the value appearing in the first file and “n2” is the value in the second file, then the absolute error is given by the formula “A=|n1-n2|”, while the relative error “R” is given by:
If the contents of a field are, in at least one of the compared files, non-numerical, then the output line reporting absolute and relative errors is replaced by the separator:
@ @@
It can happen that a line in one of the two files to compare contains more fields than the corresponding line of the other file. When this is the case, numdiff reports this difference by telling that a certain line (identified by its line number) appears to be shorter in one of the two files, just as in
##1 #>6 <== water
==>
@ Line 1 in file "list2" is shorter!
or in
##3 #>1 <==
==> A new line
@ Line 3 in file "list1" is shorter!
When this is the case, numdiff also shows the tail of the line as it appears in one of the compared files. Moreover, it uses the notation “#>n” to indicate the number n of the first field in the longer line for which there is no corresponding field in the shorter line. For instance,
##1 #>6 <== water
==>
@ Line 1 in file "list2" is shorter!
means that all the fields of the first line starting from the sixth one are empty in the second file (list2). In this context, the symbol <<*>> (when it appears) is used to denote the End-Of-File, i.e. a line or the tail of a line which is located at the end of the corresponding file and does not have a terminating newline character.
It can also happen that one of the two files to compare has less lines than the other one. In this case numdiff prints the number of the first line which compares in only one of the two files. Moreover, it prints on the standard error a message telling in which of the two files the end has been prematurely reached:
*** End of file "list1" reached
Likely the files "list1" and "list2" do not have the same number of lines !
At last, numdiff prints on standard output a message reporting the final status of the comparison. This message says either the two files are equal or they are different, just as in the example we are considering:
+++ File "list1" differs from file "list2"
I have to remark that the user can make numdiff avoid to print, partially or totally, the messages that it would otherwise send to standard output. This can be achieved by some suitable command line options, see Invoking.
To successfully compile, build and install Numdiff some tools are required. The first one is an ANSI C compiler. This compiler should at least accept the option -o in order to place its output in a specified file. Numdiff has been successfully compiled and tested on Slackware GNU/Linux 10.2 with the version 3.3.6 of the GNU C Compiler (gcc), on Slackware GNU/Linux 11 with gcc 3.4.6, and on SunOS 5.8 with the version 2.95.3 of the same compiler.
Moreover, you need a POSIX implementation of the make utility (I used both GNU make and smake by Joerg Schilling to compile Numdiff) and a POSIX implementation of the commands rm and find. At last, you need a proper installation of GNU Texinfo (in order to install the info documentation) and a shell sh-compatible.
Configuration, building and installation of Numdiff can be performed through the standard three steps:
./configure
make
make install
If you leave enabled the Natural Language Support and you also want to install the localization files (at the moment only the italian localization is supplied), then, after `make', you will have to type and run
make install-nls
By default, `make install' will install all the files in /usr/local/bin, /usr/local/info etc. You can specify an installation prefix other than /usr/local using the option --prefix in the configure step, for instance `--prefix=$HOME':
./configure --prefix=$HOME
For better control, you can use the options --bindir, --infodir, and so on. Type `./configure --help' to obtain the complete list of all the available options.
Anyway, the documentation files, including a full User Manual available in several formats (HTML, PDF and plain ASCII text), will always be put in DOCDIR/numdiff, where DOCDIR is the path specified by the option --docdir or, if this option has not been given to configure, PREFIX/local/doc. Here PREFIX is the installation prefix specified by the option --prefix or the default /usr/local.
Once Numdiff has been installed you can remove all the files previously installed by a simple `make uninstall'. If you have also installed the localization files trough `make install-nls', then, in order to remove also these ones, use `make uninstall-nls' in place of `make uninstall'.
Between the options accepted by configure there are --enable-mpa, --enable-hpa, --enable-ldpa, --enable-dpa, --enable-debug, --enable-optimization, and --enable-nls.
The option --enable-debug turns on debugging when compiling the source code. This is obtained by passing to the compiler the -g option, but you can change this default debugging flag (which could not even be recognized by your compiler) by setting the environment variable DBGFLAGS before calling configure.
The option --enable-optimization turns on basic optimization when compiling the source code. This is obtained by passing to the compiler the -O option, but you can change this default flag (which could not even be recognized by your compiler) by setting the environment variable OPTFLAGS before calling configure.
The option --enable-nls turns on Natural Language Support. But you do not need to use it explicitly, since Natural Language Support is enabled by default. However, you can disable it by using --disable-nls.
The options --enable-mpa, --enable-hpa, --enable-ldpa, and --enable-dpa are used to enable the support for, respectively, multiple precision arithmetic, high precision arithmetic, long double precision arithmetic and double precision arithmetic. By default, the support for multiple precision arithmetic is enabled if no explicit specification is given.
The support for high precision arithmetic requires the installation of HPAlib (version 1.6 or later), a free (LGPL-ed) library for high precision computations available at the web address http://savannah.nongnu.org/projects/hpalib.
Be careful ! Multiple precision arithmetic is better than high precision arithmetic. The support for high, long double and double precision arithmetic is only provided to allow running Numdiff on slow computers. Moreover, some of the features of Numdiff, which can be activated through some suitable command line options, are available only if Numdiff has been built with the support for multiple precision arithmetic. In particular, when this support is available, the user can select at runtime, by the option -#, the precision which Numdiff will have to use in doing its computations, see Invoking.
numdiff -h|v
or
numdiff [-a maxerr][-r maxerr][-2][-P][-N][-s ifs][-b][-V][-q][-D][-E]
[-I][-S][-# prec][-d c1c2][-t c1c2][-g n1n2][-p c1c2][-n c1c2][-e c1c2]
[-i c1c2][-F f1-f2][-L l1-l2][-l path][-o path] file1 file2
where file1 and file2 are the names of the two files to compare. In the first case numdiff prints a short help (actually not so short) or/and version number, Copyright, NO-Warranty disclaimer and some information about the way it was built. In the second case numdiff compares the files specified by the two (mandatory) arguments following the list of the options. The complete path of a file should be given, a directory name is not accepted. Moreover, the two arguments cannot refer to the same file but one of them can be "-", which refers to stdin.
OPTIONS
DIAGNOSTICS
The exit status is 1 if the two given files differ, 0 if they are equal, -1 (255) in case of error.
DEFAULT NUMERIC FORMAT (for both files to compare):
Decimal point = `.'
Thousands separator = `,'
Number of digits in each thousands group = 3
Positive sign = `+'
Negative sign = `-'
Prefix for decimal exponent = `e'
Symbol used to denote the imaginary unit = `i'
SOME EXPLANATIONS
The options -D, -E, -b and -q are used to hide part of the standard output of the program according to some rule.
The option -D triggers the “dummy mode”. In this mode numdiff does not print the numerical differences. A numerical difference occurs when a given field turns out to be of numerical type in both files to compare, but it has in the second file a value differing from the one contained in the first file. The “dummy mode” is so called since when it is active, numdiff does not perform the job for which I created it.
The option -E triggers the “essential mode”. In this mode numdiff only prints the numerical differences between the two files and, if there are some, the differences in the structure, which occur either when a line of text comes out to be formed by a different number of fields in the two files to compare or when the two files have a different number of lines.
The option -b triggers the “brief mode”. In this mode numdiff does not print the differences in the structure of the two files, i.e. the ones consisting in a different number of fields on a line, or in a different number of lines in the two files.
Finally, the option -q triggers the “quiet mode”. When in this mode numdiff does not print anything on the standard output. The “quiet mode” is useful if you only want to know whether a couple of files are equal or not. This information can be obtained by looking at the exit status of the program.
The option -V triggers the “verbose mode”. In this mode numdiff produces a richer report by printing an header for every line differing in at least one field in order to show how this line appears in the two compared files. For instance, if the files data1 and data2 contain the data
12 33 22 44.5 0.008 1.002 221.12 -34.56 water 2101.21 boats
and
12 33 22.3 44.5 0.008 1.202 221.12 -34.56 2101.21 boats dogs
respectively, then the command `numdiff -V data1 data2' will print the following output:
----------------
##2 <== 22 44.5
==> 22.3 44.5
##2 #:1 <== 22
==> 22.3
@ Absolute error = 3.0000000000e-1, Relative error = 1.3636363636e-2
----------------
##3 <== 0.008 1.002
==> 0.008 1.202
##3 #:2 <== 1.002
==> 1.202
@ Absolute error = 2.0000000000e-1, Relative error = 1.9960079840e-1
----------------
##4 <== 221.12 -34.56 water
==> 221.12 -34.56
##4 #>3 <== water
==>
@ Line 4 in file "data2" is shorter!
----------------
##5 <== 2101.21 boats
==> 2101.21 boats dogs
##5 #>3 <==
==> dogs
@ Line 5 in file "data1" is shorter!
+++ File "data1" differs from file "data2"
You must care that, if two or more of the options -V, -b and -q are set at the same time, then numdiff will consider valid only one of them, according to the following priority order (from higher to lower priority level): -q, -b, -V. Moreover, the amount of additional information printed by the option -V is trivially influenced by the options eventually set between the ones altering the way numdiff performs the comparisons between fields (for instance -a, -r, -2, -N, -P, -D, -E, -I, -F). In the headers printed by numdiff when in “verbose mode” can also appear the symbol <<*>>. This symbol, if present, is always located at the end of a line to mean that the line is at the end of the corresponding file and does not have a terminating newline character.
The option -S adds to the standard output of numdiff the following information:
The options -a, -r, -2, -P and -N affect the way numdiff performs the comparisons between numerical values. Without any of these options, numdiff considers two numerical fields as equal when their difference is zero.
The option -a can be used to specify that two numerical fields must be considered equal as long as their absolute difference does not exceed a given threshold, which is supplied by the argument following the -a option.
The option -r can be used to specify that two numerical fields must be considered equal as long as their relative difference does not exceed a given threshold, which is supplied by the argument following the -r option.
The option -2 is only meaningful when both -a and -r are present on the command line. If the user specifies a non-zero tolerance threshold for both absolute and relative error by using both -a and -r, numdiff adopts this behavior: it considers equal two numerical fields as long as at least one between absolute and relative error does not exceed the corresponding threshold. With the option -2 numdiff regards two numerical values as equal only if both absolute and relative error do not exceed the threshold of tolerance. For instance, if file1 contains the unique line
100
and file2 the line
100.00012
then the output of the command `numdiff file1 file2' will be
----------------
##1 #:1 <== 100
==> 100.00012
@ Absolute error = 1.2000000000e-4, Relative error = 1.2000000000e-6
+++ File "file1" differs from file "file2"
the output of the commands `numdiff -a 1.0e-4 file1 file2' and `numdiff -r 1.0e-6 file1 file2' will be the same, while `numdiff -a 1.0e-4 -r 1.3e-6 file1 file2' and `numdiff -a 1.3e-4 -r 1.0e-6 file1 file2' will print the message
+++ Files "file1" and "file2" are equal
since the actual relative error is 1.2e-6 < 1.3e-6, the actual absolute error is 1.2e-4 < 1.3e-4, and it is sufficient that one of them does not exceed the tolerance specified on the command line to make numdiff consider equal the two compared values. However, the commands `numdiff -a 1.0e-4 -r 1.3e-6 -2 file1 file2' and `numdiff -a 1.3e-4 -r 1.0e-6 -2 file1 file2' will print the message
----------------
##1 #:1 <== 100
==> 100.00012
@ Absolute error = 1.2000000000e-4, Relative error = 1.2000000000e-6
+++ File "file1" differs from file "file2"
since the option -2 makes numdiff regard two values as equal only if both absolute and relative difference do not exceed the corresponding threshold of tolerance.
The option -P makes numdiff consider two values equal whenever the second one, i.e. the one coming from the file specified as last on the command line, is less or equal than the first one, which is the value coming from the file specified as first on the command line. If the values to compare are complex numbers, saying that the second one is less or equal than the first one means that both real and imaginary part of the second one are not greater than the real part and, respectively, the imaginary part of the first one.
Finally, the option -N makes numdiff consider two values equal whenever the second one, i.e. the one coming from the file specified as last on the command line, is greater or equal than the first one, which is the value coming from the file specified as first on the command line. If the values to compare are complex numbers, saying that the second one is greater or equal than the first one means that both real and imaginary part of the second one are not less than the real part and, respectively, the imaginary part of the first one.
The options -I, -l, -o, -h and -v do not require further explanations. The options -l and -o are only supplied for the users of some poorly designed operating systems (like MSDog or MSWindoze), whose default shell does not allow the redirection of standard error and standard output. The option -I has no effect on the outcome of numerical comparisons.
Several things must be told about the option -s. First, it will be better if you will always quote the set of the delimiters, just as in the next examples:
numdiff -s ' \t\n,;:.' file1 file2
numdiff -s ' \t\n\r\f\v"\:;' file1 file2
numdiff -s `` \t\n''' file1 file2
I recommend you actually to always use the single quote character (') to enclose the list of the delimiters, since in this way you will prevent any substitution or handling of characters by the shell.
numdiff recognizes and interprets the following sequences of characters within the argument passed to the option -s:
since these characters are often used as delimiters in files containing numerical data and they could not be included directly in the set of delimiters. Then, by passing the string ` \t\n,;:.' as argument for the option -s, one tells numdiff use as field delimiters the characters blank, horizontal tab, newline, comma, semicolon, colon and dot. Passing ` \t\n' as argument to the option -s is the same as not using at all the option -s, since blank, horizontal tab and newline are the default field delimiters. In the list of field delimiters the character backslash (`\') is always treated in a special way. If followed by `f', `n', `r', `t' and `v' it is combined with the subsequent character and interpreted in the way we have just seen. Otherwise, the backslash is coupled with the following character and then removed. In particular, if you want to specify the backslash itself as field delimiter, you have to put two backslashes (`\\') in the list of delimiters. Therefore, the delimiters specified by the command line
numdiff -s' \t\n\\\"' file1 file2
are blank, horizontal tab, newline, backslash and double quote since `\\' and `\"' are interpreted by numdiff as `\' and `"'.
Even if I have recommended to enclose the set of delimiters in single quotes, there are cases in which you will be constrained to use the double quote character (`"') to enclose the set of field delimiters, just as in one of the previous examples. However you must take into account that in this case the shell could make some substitutions on the command line before executing numdiff. For instance, if your shell is GNU bash, then (citing the man page of GNU bash)
Enclosing characters in double quotes preserves the literal value of all characters within the quotes, with the exception of `$', ``', and `\'. The characters `$' and ``' retain their special meaning within double quotes. The backslash retains its special meaning only when followed by one of the following characters: `$', ``', `"', `\', or <newline>. A double quote may be quoted within double quotes by preceding it with a backslash .... The special parameters * and @ have special meaning when in double quotes ...
Therefore, if the set of delimiters is formed by ` ', `\t', `\n', `\' and `"' and you decide to enclose them in double quotes, then the numdiff command line should be
numdiff -s'' \t\n\\\\\"'' file1 file2
and not
numdiff -s'' \t\n\\\"'' file1 file2
Indeed, in this last case the shell would replace the string
` \t\n\\\"'
with
` \t\n\"'
and then numdiff would take ` ', `\t', `\n' and `"' as field delimiters.
A last advice about the use of the option -s. I recommend you to always put newline (on Unix© and Unix-like operating systems, like GNU©) and carriage return (on MSDog/MSWindoze) in the set of field delimiters. Otherwise, these characters would be included in all the fields staying at the end of a line and this would cause some undesirable effects. For instance, a number put at the end of a line would not be considered as a numerical field by numdiff, since numdiff would consider the final newline as part of the field which then would be qualified as non-numerical. Maybe in the future I will modify numdiff in order to remove the mandatory specification of newline as field delimiter.
The options -#, -d, -t, -g, -p, -n, -e and -i are only meaningful if numdiff has been built with the support for Multiple Precision Arithmetic, see Installing. If this is not the case, then numdiff will simply ignore them and, for what concerns the numeric format, it will always use the default one for both files to compare while the precision of the computations will be the one chosen when numdiff was compiled. You can know whether numdiff has or has not been compiled with the support for Multiple Precision Arithmetic through the option -v.
The option -# lets the user specify the number of digits in the significands used in multiple-precision arithmetic. The default value is 35, the largest admissible value is 180. Take into account that an higher precision makes the execution of numdiff slower. This is particularly true when the files to compare contain a lot of numerical fields. Moreover, you have to care that numdiff can truncate the value of a numerical field if it has too much digits with respect to the current precision. To be precise, denoted by P the current value of the precision:
The options -d, -t, -g, -p, -n, -e and -i can be used to instruct numdiff about the numeric formats used in the files which it is going to compare. The two files to compare do not have to adopt the same numeric format, and then numdiff allows to specify different numeric formats for them. Indeed each of the options -d, -t, -g, -p, -n, -e and -i can have as argument one or two characters (one or two digits if the option is -g). In the first case, the argument refers to both files to compare, in the second one the first character is for the file specified as first on the command line, the second character is for the file specified as last one on the command line. For instance, the option -d can be used to tell numdiff which character(s) is(are) used to mean the decimal point in the two files to compare. If you give the command `numdiff -d_ file1 file2', then numdiff will understand that both in file1 and file2 the character underscore (`_') is used in place of the default one (`.') to indicate the position of the decimal point in the numerical values. But if the command is `numdiff -d_: file1 file2', then numdiff will understand that the decimal point is indicated by the character underscore in file1, and by colon (`:') in file2.
Naturally, if you omit to use one of the options -d, -t, -g, -p, -n, -e and -i, then the corresponding attribute will take its default value, see Default Numeric Format.
You must be really careful when you use one or more
of these options.
First, not all characters can be passed to them as arguments.
For instance, the arguments of the option -g
must be digits.
The arguments of the options -d and -t must
be punctuation marks (the punctuation marks are all the
characters of the ASCII set for which the standard C function
ispunct returns a non zero value), those ones
of the options -p, -n, -e and -i
must be graphical characters but digits (graphical characters
are all the characters of the ASCII set for which the standard C function
isgraph returns a non zero value).
Moreover, it is not possible to set the decimal point, the thousands separator, the positive sign, the negative sign, the prefix for decimal exponent and the symbol of the imaginary unit so that, for a same file, two or more of these characters come out to be equal. This rule also applies when you miss to explicitly set one of the previous arguments through the appropriate option. For instance, the command `numdiff -d,. file1 file2' will make numdiff abnormally terminate after printing the error message:
The numeric format specified for the first file is illegal,
the following symbols should be all different
while two or more of them are actually equal:
Decimal point = `,'
Thousands separator = `,'
Positive sign = `+'
Negative sign = `-'
Prefix for decimal exponent = `e'
Symbol used to denote the imaginary unit = `i'
Indeed, through the option -d we have told to numdiff that in the first file the decimal point is indicated by the character comma, but at the same time we have not modified the character in use to separate the groups of thousands, which has remained the default one, i.e. comma, for both files to compare. In this way, we have implicitly told to numdiff that in file1 the character comma represents both decimal point and thousands separator. Since this is not reasonable, numdiff refuses to work. To avoid this problem it would be sufficient to explicitly notify to numdiff the thousands separator through the option -t: `numdiff -d,. -t., file1 file2'. Of course, here we are supposing that the decimal point and the thousands separator are represented in file1 by comma and dot respectively, in file2 by dot and comma. I strongly suggest you that in writing a file you avoid the use of the same symbol to mean two different things (like would be using comma for both decimal point and thousands separator): it would be dummy, would not it ? :)
At last, it is possible (but it is stupid) to use as argument for the options -d, -t, -g, -p, -n, -e and -i one of the characters used to separate the fields in the files to compare. In a such case numdiff does not complain but you have to consider that first it uses the set of field delimiters in order to split the files into fields and then it takes into account the numeric formats specified for the two files when it has to distinguish between numerical and non-numerical fields. However, it should never happen to specify as argument for one of the options -d, -t, -g, -p, -n, -e and -i a character which is also used as field delimiter: again, in writing a file you should avoid (and people usually avoid it) to use the same symbol to mean two different things.
The options -L and -F can be used to restrict the comparison between files to a certain range of lines or to a certain group of fields. Without these options numdiff compares all the fields of all the lines.
With the option -L the user can make numdiff restrict the comparison to a certain line or to a certain range of lines. For instance `numdiff -L 5 file1 file2' will make numdiff compare only the fields in the fifth line of file1 with the corresponding fields in the fifth line of file2.
Similarly `numdiff -L 5-10 file1 file2' will make numdiff compare only the fields which are contained in the lines from 5 to 10.
As you can see, you can specify a range of lines by using the notation `n1-n2', where n1 and n2 are the line numbers of the first and of the last line in the range of lines that you want to compare.
If you use two or more times the option -L with different specifications, then numdiff will only consider the last specification. Therefore `numdiff -L 5-10 -L 6 -L 10-20 file1 file2' will make numdiff compare the fields in the lines from 10 to 20.
With the option -F the user can make numdiff restrict the comparison to a certain field or to a certain group of fields. For instance `numdiff -F 3 file1 file2' will make numdiff compare only the third field of each line of file1 with the third field of the corresponding line of file2.
Similarly `numdiff -F 3-7 file1 file2' will make numdiff compare, for every line in file1 and file2, only the fields from the third one to the seventh one (both included).
As you can see, you can specify a range of fields by using the notation `n1-n2', where n1 and n2 are the field numbers of the first and of the last field in the range of fields that you want to compare.
Remember that the fields of a line are numerated starting from the left hand of the line and proceeding towards the right hand.
By using two or more times the option -F you can extend the comparison to a group of fields formed by more ranges and/or single fields. For instance `numdiff -F 5-10 -F 6 -F 12-20 -F 4 file1 file2' will make numdiff compare the fourth field, the fields from the 5th one to the 10th one and the fields from the 12th one to the 20th one of every line. Care the difference with respect to the option -L, since, as I told above, if you use two or more times the option -L only the last specification will be considered by numdiff.
Moreover, take into account that the largest field number that you can use while writing a specification for the option -F is 32768.
Of course, you can use the options -F and -L together. In this way you can restrict the comparison to a certain group of fields within a certain range of lines.
If you use the option -F and/or the option -L the exit status of numdiff will reflect the outcome of the restricted comparison. For instance, the exit status of `numdiff -L 1-7 file1 file2' will be 1 only if numdiff will have found a difference in the first seven lines of file1 and file2. If the two files differ only in the lines after the seventh one, then numdiff will end with a zero exit status.
If the number is written in common notation, then numdiff will consider, in addition to all the digits of the integer part, only the first P digits of the fractional part.
If the value is written in scientific notation, then numdiff will only consider the first P digits of the fractional part of the mantissa.
By current value of the precision I mean the integer value specified by the option -#, or the default one (35) when this option is not in use.
Line 1 in file "list2" is shorter:
<== water
==>
the current format is given by
##1 #>6 <== water
==>
@ Line 1 in file "list2" is shorter!
Moreover, the versions of Numdiff preceding 4.0.0 did not provide the “verbose mode” with the related option -V. Finally, in the passage from the version 3.0.2 to the 4.0.0 one a minor bug related to the handling of the last line of a file has been corrected.
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Permission is granted to copy, distribute and/or modify this document
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