Learning Linux/Unix with man(1)

A Crash Course in Unix

You really can learn a lot from the unix man pages. In addition to the basic usage of a command, the man page also shows what environment variables it uses, gives some examples, and lists some related commands. I've been using one unix variant or another for more than 15 years and I've learned oodles from man pages.

Here's a brief list of essential commands that should help you lots:

• man - but how do you read the man page if you've never used the man command? Here's a quick start:
  • At the shell prompt, type "man man" to view the manual page (more frequently called just "man page") for the man command.
  • The man command displays the man page using a paging program, usually less, so that it doesn't scroll past too quickly to be read.
  • To navigate the pages, press the space bar or page down to move down, "b" or page up to move up. Hit "q" to quit and return to the shell prompt.

  At the bottom of most man pages is a section called "SEE ALSO". This is a good place to find related commands. If you're reading man pages through a web interface or another more interactive UI, these may be hyperlinked to their man pages.

• less - Hint: while viewing man page for less, hit "/" then type "Search" to search for how to search when inside less. This is very useful when reading man pages. Other good things to learn from this man page include how to go to the next occurrence of your search term, how to specify that case is significant or insignificant, and how to got to the beginning or end of the file.

• bash - the default shell for every Linux installation I've ever used. This is a very large man page. Focus in on some of the more important builtin commands which are documented on this page, such as:
  • alias
  • type
  • pwd
  • pushd
  • popd
  • dirs
  • export
  • history
  • kill
  • echo
  • cd
  Note: kill, echo and cd are also standalone executables, use "type" to determine which you run - most likely the builtin or an alias
• grep
• ps
• ls
• find
• cat
• wc
• head
• tail
• w
• last
• awk
• tar
• diff
• which
• wget
• sort
• uniq

Then you can string some of these together to get a list of unique IP addresses that requested /node/100647 out of an access log, try:

% grep /node/100647 access.log | awk '{ print $1 }' | sort | uniq -c

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Other readings:

• Package (e.g. rpm) and software update commands (e.g. apt-get, urpmi, yum) which are distro specific

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Doug Harris