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@@ -0,0 +1,67 @@ +Frequently Asked Questions +-------------------------- + +Why use man-db instead of man? +============================== + +The man (currently http://primates.ximian.com/~flucifredi/man/) and man-db +packages forked from a common code base in the mid-1990s. The original goal +of man-db was, as indicated by the name, to add database caching to manual +page searches. The increase in computer performance has considerably +outpaced the growth of manual page collections, so some people now ask what +the point is of using man-db rather than man. + +These days, the database is indeed not such an important difference between +man-db and man, but there are several other areas where man-db does a +significantly better job than man: + + * Internationalisation + + man uses the obsolete catgets system for translations of the messages + emitted by its programs, which cannot deal with the user using a + different output encoding (e.g. UTF-8) from that provided by the + translators. man-db uses gettext, which is more correct and robust. + + In order to support many cases of non-English manual pages, man requires + manual hardcoding of iconv pipelines (or similar) and *roff device names + in its configuration file, and cannot operate correctly in environments + involving a variety of encodings. man-db handles all this out of the + box. + + * Security and code quality + + Security matters because both man and man-db can be installed setuid to + a special user, and also because man is sometimes used in semi-trusted + or untrusted contexts, such as from CGI scripts. + + Both man and man-db spend a lot of time calling external programs, often + in pipelines. man does so by assembling strings which it then feeds to + the shell; this approach is nowadays well-known to be fragile and prone + to security vulnerabilities. man-db has been redesigned from top to + bottom to have safe and correct command execution, using a special + "libpipeline" library. + + * Performance + + Happily, dealing with manual pages is not normally a + performance-critical task these days; manual pages can normally be found + and rendered comfortably within expected interactive response times. + However, there are a few cases that are still more difficult, such as + 'man -K' to perform a full-text search on all manual pages. Neither man + nor man-db includes a proper full-text search engine, but there is + nevertheless a significant performance difference here: man-db performs + this search at least three times as quickly as man, and in some cases + much better than that. (On the test system, man took five minutes to + search all manual pages, severely degrading interactive performance of + the rest of the system for that time; man-db took around 40 seconds.) + + * Maintenance + + At the time of writing (February 2012), man-db has had ten full releases + since the start of 2008 with substantial feature work, while man has had + one release with a few minor changes. + +I have great respect for the people who maintain man, but as a project it +has fallen badly behind. Rather than continuing to struggle along with +complicated patch sets, those distributions that still use man would +probably be better off switching to man-db. |