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Sunday, March 31, 2013

Fetching Information on Commands in Nix

The "info" is a great utility for getting information about the system.
     Here's a quick key on using "info" from the terminal prompt.

       'q' exits.
       'u' moves up to the table of contents of the current section.
       'n' moves to the next chapter.
       'p' moves to the previous chapter.
       'space' goes into the selected section.

      The following is a good starting point:

        $ info coreutils

      Need to find out what a certain program does?

        $ whatis  open
       open   (2)  - open and possibly create a file or device
       open   (3)  - perl pragma to set default PerlIO layers for input and output
       open   (3pm)  - perl pragma to set default PerlIO layers for input and output
       open   (n)  - Open a file-based or command pipeline channel

      To get specific information about the open commmand

        $ man 2 open

       also try 'keyword' search, which is the same as the apropos command.
       For example, to find all the man pages on selinux, type the following:

        $ man -k selinux

       or the man full word search. Same as whatis command.

        $ man -f <some string>

       This is a hint once you are inside man.

        space      moves forward one page
        b          moves backward
        y          scrolls up one line "yikes, I missed it!"
        g          goes to the beginning
        q          quits
        /<string>  search, repeat seach n
        m          mark, enter a letter like "a", then, ' to go back
        '          enter a letter that is marked.

       To get section numbers

        $ man 8 ping

       Note the numbers are used as follows
         (This is OpenBSD)

         1  General Commands
         2  System Calls and Error Numbers
         3  C Libraries
         3p perl
         4  Devices and device drivers
         5  File Formats and config files
         6  Game instructions
         7  Miscellaneous information
         8  System maintenance
         9  Kernel internals

       To find the man page directly, "ls" command:

         $ whereis -m ls
         ls: /usr/share/man/man1/ls.1.gz /usr/share/man/man1/ls.1 /usr/share/man/man1p/ls.1p

       To read this file directly, do the following:

         $ man /usr/share/man/man1/ls.1.gz

       If you want to know the manpath, execute manpath.

         $ manpath