Replace tab characters by spaces in your text files with a free open source command line tool for Windows, Mac OS X and Linux.

sfk detab=tabsize dir ext1 [ext2 ...] [-to outmask]

replace tabs by spaces within file(s) or text stream.

options
   -to outmask   do not overwrite original files, but write
                 to output files according to outmask, e.g.
                 -to tmp\$path\$base.$ext or -to tmp\$file
   -yes          if files are selected, really (re)write them.
                 without -yes, detab is only simulated.
   -memlimit=n   process files with up to n mbytes (default=300).
   -nowarn       do not tell about skipped or unreadable files.

see also
   sfk scantab   list files containing TAB characters.
   sfk help opt  how to change the memlimit permanently.
   sfk view      a text file viewer that can show all TAB
                 characters in blue by pressing CTRL+T.

web reference
   http://stahlworks.com/sfk-detab

examples
   sfk detab=3 sources .cpp .hpp
      replace tabs by up to 3 blanks, within all .cpp and .hpp
      files of directory tree "sources".

   sfk select -dir src -file .java +detab=4 -to tmp\$file
      list all .java files of src, then detab with tabsize 4,
      writing all outputs to directory tree "tmp".

   sfk detab=4 src .java -relnames -to tmp\$file
      nearly the same, however stripping the "src" input directory
      name from output file paths (not possible with "+detab" form).

   sfk filter mytext.txt +detab=8
      detab content of a single file to the console.
 
to find how many files would need detabbing, type for example:

   sfk scantab testfiles .hpp .cpp .txt
     -> scans directory testfiles, and all subdirectories,
        for .hpp, .cpp and .txt files containing tab characters.

   example output:
      list of files containing tabs:
      testfiles\Formats\01-native-tab-crlf.txt
      testfiles\Formats\02-crlf.txt
      testfiles\Formats\03-native-tab-lf.txt
      testfiles\Formats\04-lf.txt
      testfiles\Formats\08-head-tail.txt
      testfiles\Formats\20-tab-data-line.txt
      6 files of 32 contain tabs.

to view TAB characters in your files interactively like this:

   

   - download the free text browser Depeche View Base.
   - click on "Open", select the folder containing your text files.
   - click on the "showtab" button in the right bottom corner.

   All TAB characters will be shown in blue, and all blanks in yellow.

to search for TAB characters interactively:

   Within Depeche View, use the TAB keyword in your queries, e.g.

   -  type "TAB " to find all TAB characters.
      (Type it all uppercase, and don't forget the blank after TAB)

   -  type "TAB }" to find all curly brackets } preceeded by a tab:

   

   -  type "foo TAB bar" to find the word combination "foo" and "bar"
      with exactly one TAB character inbetween. Note that the blanks
      around "TAB" are not used in the search.