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A conservative interactive spell checker for source code.

Project Description

scspell is a spell checker for source code. This is an unofficial fork (of that runs on both Python 2 and 3.

scspell does not try to be particularly smart–rather, it does the simplest thing that can possibly work:

  1. All alphanumeric strings (strings of letters, numbers, and underscores) are spell-checked tokens.
  2. Each token is split into one or more subtokens. Underscores and digits always divide tokens, and capital letters will begin new subtokens. In other words, some_variable and someVariable will both generate the subtoken list {some, variable}.
  3. All subtokens longer than three characters are matched against a set of dictionaries, and a match failure prompts the user for action. When matching against the included English dictionary, prefix matching is employed; this choice permits the use of truncated words like dict as valid subtokens.

When applied to code written in most popular programming languages while using typical naming conventions, this algorithm will usually catch many errors without an annoying false positive rate.

In an effort to catch more spelling errors, scspell is able to check each file against a set of dictionary words selected specifically for that file. Up to three different sub-dictionaries may be searched for any given file:

  1. A natural language dictionary. (scspell provides an American English dictionary as the default.)
  2. A programming language-specific dictionary, intended to contain oddly-spelled keywords and APIs associated with that language. (scspell provides small default dictionaries for a number of popular programming languages.)
  3. A file-specific dictionary, intended to contain uncommon strings which are not likely to be found in more than a handful of unique files.


To begin the spell checker, run

$ scspell source_file1 source_file2 ...

For each spell check failure, you will see output much like this:

filename.c:27: Unmatched 'someMispeldVaraible' -> {mispeld, varaible}

In other words, the token “someMispeldVaraible” was found on line 27 of filename.c, and it contains subtokens “mispeld” and “varaible” which both failed the spell-checking algorithm. You will be prompted for an action to take:

Skip to the next unmatched token, without taking any action.
(I)gnore all
Skip over this token every time it is encountered, for the remainder of this spell check session.
Enter some text to use as a replacement for this token, and replace only the token at this point in the file.
(R)eplace all
Enter some text to use as a replacement for this token, and replace every occurrence of the token until the end of the current file.
(a)dd to dictionary
Add one or more tokens to one of the dictionaries (see below).
show (c)ontext
Print out some lines of context surrounding the unmatched token.

If you accidentally select a replacement operation, enter an empty string to cancel.

If you select the (a)dd to dictionary option, then you will be prompted with the following options for every subtoken:

Return to the previous menu, without taking any action.
Skip to the next subtoken, without taking any action.
add to (p)rogramming language dictionary
Add this subtoken to the dictionary associated with the programming language of the current file. scspell uses the file extension to determine the language, so you will only see this option for files which have an extension.
add to (f)ile-specific dictionary
Add this subtoken to the dictionary associated with the current file. You will see this option only for files which have such an embedded ID or which have an entry in the file ID mapping. See Creating File IDs for details.
add to (N)ew file-specific dictionary
Create a new file ID for the current file, record the new file ID in the file ID mapping, and add this subtoken to a new file-specific dictionary associated with that file ID. You will see this option only for files which have neither an embedded ID nor an entry in the file ID mapping, and only if the --relative-to option is given. See Creating File IDs for details.
add to (n)atural language dictionary
Add this subtoken to the natural language dictionary.

If scspell finds no unknown tokens, it exits with exit status 0. If there were unknown tokens, it exits with exit status 1. If it terminates in response to a (handled) signal such as a SIGINT from ^C, it exits with exit status 2.

Spell-checking Options


This option causes scspell to report to stderr a report of the subtokens that it considers to be in error, instead of offering the interactive menu described above. For each subtoken, the report includes the filename, line number, and full token. scspell will exit with an exit code of 1 if any errors are found, or 0 if the run was clean.

The format of the reported errors is different than the interactive mode reports them. With --report-only, the above one would appear like this:

filename.c:27: 'mispeld', 'varaible' were not found in the dictionary (from token 'someMispeldVaraible')

By default, scspell treats files as if they contain C-style character escapes. That is, given printf("Hello\nworld."), it will consider the tokens “hello” and “world”, not “nworld”.

The --no-c-escapes option causes scspell to not treat \ as a special character, for e.g. LaTeX files where you might write \Alpha\beta\gamma\delta. Without this option, scspell would see the tokens “lpha”, “eta”, “amma”, and “elta”.

Creating File IDs

If you would like scspell to be able to uniquely identify a file, thus enabling the creation of a file-specific dictionary, then scspell must be able to find a file ID to identify both the file an the file-specific dictionary. There are two ways scspell can find the file ID:

  1. The file ID may be embedded directly in the file, using a string of the following form:

    scspell-id: <unique ID>
  2. An entry in the file ID mapping file ties a filename to a file ID.

The unique ID must consist only of letters, numbers, underscores, and dashes. scspell can generate suitable unique ID strings using the --gen-id option:

$ scspell --gen-id
scspell-id: e497803c-523a-11de-ae42-0017f2ee0f37

(Most likely you will want to place a file’s unique ID inside a source code comment.)

During interactive use, the (a)dd to dictionary -> add to (N)ew file-specific dictionary option will create a new File ID for the current file, and add it to the file ID mapping file.

–relative-to RELATIVE_TO
The filenames stored in the file ID mapping are relative paths. This option specifies what they’re relative to. If this option is not specified, the file ID mapping will not be consulted, and the add to (N)ew file-specific dictionary option will not be offered.

Managing File IDs

These options direct scspell to manipulate the file ID mapping. (These can all be accomplished by editing the file ID mapping manually). These have no effect on file IDs embedded in files.

–rename-file FROM_FILE TO_FILE
Changes the filename that a File ID maps to. After renaming a file that has a file-specific dictionary and an entry in the file ID mapping, you can use this option to have the entry “follow” the file.
Remove filenames from the file ID mapping. If it was the only filename for a given File ID, removes the File ID from the mapping and its wordlist from the dictionary.
–merge-file-ids FROM_ID TO_ID
Combines the file-specific dictionaries referenced by the two File IDs. All words from FROM_IDs list are moved to TO_IDs. The FROM_ID File ID is removed from the mapping, and any files using it are changed to use TO_ID. Either FROM_ID or TO_ID may be given as a filename instead, in which case that file’s File ID is used for that parameter.

Sharing a Dictionary

A team of developers working on the same source tree may wish to share a common dictionary. You can permanently set the location of a shared dictionary by executing

$ scspell --set-dictionary=/path/to/dictionary_file.txt

The dictionary is formatted as a simple newline-separated list of words, so it can easily be managed by a version control system if desired.

The current dictionary can be saved to a file by executing

$ scspell --export-dictionary=/path/to/output_file.txt

You can also override the dictionary location for a single spell check session, by using the --override-dictionary option:

$ scspell --override-dictionary=/path/to/dictionary_file.txt source_file1 ...
–base-dict BASE_DICT

A base dictionary is consulted for its words, but is not modified at runtime. By using

$ scspell –base-dict ~/.dict –override-dictionary proj/.dict source…

words added at runtime will be added to proj/.dict, and ~/.dict will be left alone. This way proj/.dict may be limited only to the words added for proj/. This may be more convenient when proj/.dict is committed to source control and shared by many users.

Use the dictionary file shipped with scspell as a base dictionary.

Read the dictionary specified by the normal dictionary selection options, called the project dict here. Read the base dictionaries specified by the base-dict options. Remove from the project dict all the words from the base dicts, and write the project dict back out.

This may be useful when a project dict has been generated with an older version of scspell that did not support base dicts.


Install scspell via pip:

$ pip install scspell3k

Alternatively, download and unpack the source archive, switch to the archive root directory, and run the installation script:

$ python install

On a UNIX-like system, you may need to use sudo if installing to a directory that requires root privileges:

$ sudo python install


scspell is Free Software, licensed under Version 2 of the GNU General Public License; see COPYING.txt for details.

The English dictionary distributed with scspell is derived from the SCOWL word lists . See SCOWL-LICENSE.txt for the myriad licenses that apply to that dictionary.

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