Editing Pipeline (Unix) (section)

=== Example ===
Below is an example of a pipeline that implements a kind of [[spell checker]] for the [[World Wide Web|web]] resource indicated by a [[Uniform Resource Locator|URL]]. An explanation of what it does follows.

<syntaxhighlight lang="bash" line="">
curl 'https://en.wikipedia.org/wiki/Pipeline_(Unix)' |
sed 's/[^a-zA-Z ]/ /g' |
tr 'A-Z ' 'a-z\n' |
grep '[a-z]' |
sort -u |
comm -23 - <(sort /usr/share/dict/words) |
less
</syntaxhighlight>

# '''<code>[[CURL|curl]]</code>''' obtains the [[HTML]] contents of a web page (could use <code>[[wget]]</code> on some systems).
# '''<code>[[sed]]</code>''' replaces all characters (from the web page's content) that are not spaces or letters, with spaces. ([[Newline]]s are preserved.)
# '''<code>[[tr (program)|tr]]</code>''' changes all of the uppercase letters into lowercase and converts the spaces in the lines of text to newlines (each 'word' is now on a separate line).
# '''<code>[[grep]]</code>''' includes only lines that contain at least one lowercase [[alphabetical]] character (removing any blank lines).
# '''<code>[[Sort (Unix)|sort]]</code>''' sorts the list of 'words' into alphabetical order, and the <code>-u</code> switch removes duplicates.
# '''<code>[[comm (Unix)|comm]]</code>''' finds lines in common between two files, <code>-23</code> suppresses lines unique to the second file, and those that are common to both, leaving only those that are found only in the first file named.  The <code>-</code> in place of a filename causes <code>comm</code> to use its standard input (from the pipe line in this case). <code>sort /usr/share/dict/words</code> sorts the contents of the <code>words</code> file alphabetically, as <code>comm</code> expects, and <code>&lt;( ... )</code> outputs the results to a temporary file (via [[process substitution]]), which <code>comm</code> reads. The result is a list of words (lines) that are not found in /usr/share/dict/words.
# '''<code>[[less (Unix)|less]]</code>''' allows the user to page through the results.