Make Good Use of Online Document man and info
In a previous blog I mentioned that we really want to make good use of Internet search engines, especially google. In this blog, I want to point out that the online help systems (man and info) are also very useful. In fact, in many cases they are more convenient and more accurate. Being able to use them is crucial to boost one's productivity.
Manual is easier to access and more focused
The other day, a colleague asked me why file
test.txt exists and
[ -e test*
] returns true but
[[ -e test* ]] return false (btw. neither is correct in
terms of good shell coding). I did know the reason either. However, I figured
out the answer within one minute by checking out the manual (
info bash and
[[). The manual clearly stated that "Word splitting and filename
expansion are not performed on the words between …".
There is no need to search and screen results. And, it is also feasible even when you have no Internet access. What is more, the manual describes exactly the version you are using.
"info" provides much more info than "man"
It is also worth noting that we are usually better off using
info because it
usually provides a full documentation of designated topic. For instance, one
colleague copied a sed code snippet which uses
\+ from internet but that
code seemed does not work. He "man-ed" and determined that sed does not
\+ and turned to me for help. Once again, I instantly found
the answer in
info. In the "Regular Expressions" section of info of sed, it
\+ is supported as a GNU extension. In contrast, searching
\+ in the man page of sed gets no result.
Learn a little bit "info"
info is handy and useful only if you know how to use it. Fortunately, it is
very easy to learn: either
man info or
info info. However, be warned that
you cannot get started without skimming through the manual. And, especially
good for Emacs users, Emacs has a very good interface to
C-h i in Emacs brings you to it.
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