mch is a simple command for text manipulation.
mch reads from the stdin line by line, matching each one against the input pattern (specified by -i).
If a line is fully matched it will be printed out to the stdout based on the output pattern (specified by -o).
In the input pattern, everything except $ is matched as it is, while $ matches 0 or more chars until it meets its following char.
For exmaple, the $ in $c matches anything as long as it's not c.
In the output pattern, $ followed by a number refers to the string that is matched by its counterpart in the input pattern.
The number works as an index starting from 1; $0 refers to the whole line. As in the input pattern everything else is what it is, no escape is available.
mch doesn't support unicode.
# Example: extract uri from nginx access log
$ echo '123.65.150.10 - - [23/Aug/2010:03:50:59 +0000] "POST /wordpress3/wp-admin/admin-ajax.php HTTP/1.1" 200 2 "http://www.example.com/wordpress3/wp-admin/post-new.php" "Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10_6_4; en-US) AppleWebKit/534.3 (KHTML, like Gecko) Chrome/6.0.472.25 Safari/534.3"' | mch -i '$ $ $ [$] "$ $ $"$' -o '$6'
/wordpress3/wp-admin/admin-ajax.php
# Example: csv -> tsv (tab is entered by C-v [TAB])
$ echo 'col1,col2,col3' | mch -i '$,$,$' -o '$3 $1'
col3 col1