2017-07-23:

1. Overview
This is a small utility for generating FFT of ASCII files or standard in. The output is either to file or std out. The build is static, so no complicated dependencies must be fulfilled and thus it should be possible to use the binary with any distribution that runs on x86 or x86_64.

2. Installing
To install, just copy the binary someplace where the system finds it (e.g. in your path.)

3. Examples of use
The following call to fft

  $> fft < input.txt > output.txt

will consider the first column in the data file input.txt as the real-valued time-series to be transformed.

  $> fft -i input.txt -o output.txt -c

Same as above, except the option "-c" tells fft to interpret the input as complex data. The first and second columns are now interpreted as real and imaginary compomnets of a complex time-series.

  $> fft --input-file input.txt --output-file output.txt \
         --complex -x 3 -y 6 --delimiter , --ordered-x-axis

Using the long options. In this example the data columns are separated by ','. The data is retrived from column 6 and 7 and column 3 is used to infer the frequency. Please note that the option --delimiter refers to the format of the output file. If the input file has another format, this is specified by the option --input-delimiter. 

In this example a x-column is specified. This instructs fft to treat that column as the time coordinate. Currently, all that is done is to calculate the average sample rate from the first and last values in this column and use that to generate a frequency axis for the output.

The "natural" way for fftw is to write the negative frequencies "to the right" of the positive ones (i.e. something like  [0,..,F,-F,..,0]). The option --ordered-x-axis tells fft to start with the negative frequencies (i.e. something like  [-F,..,0,..,F]). 

4. Building from Source

fft depends on several things, which are listed below:

  a) CMake is the (meta-)build system (www.cmake.org)
  b) fftw is required for the actual FFT'ing (www.fftw.org).
     Please not that you need version 3.3 of the fftw library.
     It can be downloaded at www.fftw.org. For windows, they
     provide pre-compiled libraries. Note that the version
     shipped with Oneiric (Ubuntu 11.10) is not sufficient.
  c) boost for handling program options and other things
     like lexical cast (www.boost.org).
  d) Git. you can get the sources from github. 
     However, during build a version file is generated that is included
     in the sources. In order to generate this version header, git
     is required. Currently, it only works with the git client under Linux.
  e) The gcc c++ tool chain under Linux. 

Talk about standing on the shoulders of giants! Anyway, if you have all these prerequisites set up properly, all you need to do is:

4.1: Check out the sources by issuing the following command:

  $> git clone https://github.com/jonolafur/cli-fft.git

That should leave you with the source tree root at cli-fft (you can of course replace cli-fft with anything you like).

4.2: cd to the root of the source tree and create a build directory there (Alternatively, you can do a clean out-of-source build):
  $> mkdir build
  $> cd build

4.3: In the build directory issue the command
  $> cmake ../ -DCMAKE_BUILD_TYPE=release
If there are any issues with the pre-requisites, cmake will tell you about it at this stage. If this goes smoothly, you just have to make:

  $> make

That's it. The binary should now be located in the root of your build tree. You can copy it to somewhere where the system finds it.
 
5. Potential sources of pain

Boost missing: The standard installation of boost is probably not enough. If cmake
complains that it cannot find it, you probably need to install some more boost. Look for libboost-program-options in your package manager.

FFTW too old: If the compiler complains that the functions fftw_import_wisdom_from_filename or fftw_export_wisdom_to_filename cannot be found, you probably don't have fftw 3.3 installed. Please download it at fftw.org and compile and install it (it is very easy!). Set it up so that cmake will find it under /usr/local.