spell

Check spelling in a file

$ spell [file.txt]

$ echo "[text to check]" | spell

$ spell -b [file.txt]

$ spell +[custom_words.txt] [file.txt]

$ spell -v [file.txt]

$ spell -x [file.txt]

$ spell [file1.txt] [file2.txt]

spell [-bilvx] [+localfile] [file_...]

spell is a classic Unix spell-checking utility that reports misspelled words. It reads text from files (or stdin if none specified), looks up each word in its dictionary, and outputs words that are not found or cannot be derived from known words.
Unlike modern spell checkers such as aspell or ispell, spell does not suggest corrections or offer an interactive interface. It simply lists unrecognized words to standard output, making it suitable for scripting and batch processing.
The program recognizes common inflections, prefixes, and suffixes, so it can identify valid derivations of dictionary words. The -v option shows words that are derivable but not literally in the dictionary, while -x displays the stems used for derivation.
A custom word list can be specified with +filename to supplement the system dictionary with domain-specific or technical terms.

-b

Use British spelling rules (colour, centre, -ise endings)

Ignore troff/nroff formatting constructs

Follow chains of included files

Print all words not literally in the dictionary, including plausible derivations

Print plausible stems, one per line, preceded by =

Use additional word list; words found here are not reported as misspellings

spell provides no spelling suggestions and no interactive correction. It may flag proper nouns, technical terms, and abbreviations as misspellings. The dictionary coverage varies by distribution. For more sophisticated spell checking, consider aspell or ispell.

spell was developed by Stephen C. Johnson at Bell Labs and first appeared in Version 6 Unix in 1975. It was one of the earliest text-processing utilities and helped establish Unix as a document preparation system. The command has remained largely unchanged, preserving its simple, filter-based design philosophy.

aspell(1), ispell(1), hunspell(1), look(1)