Showing posts with label Unix Basics. Show all posts
Showing posts with label Unix Basics. Show all posts

Wednesday, November 16, 2011

What's up with Vi

Continuing with my last few posts on basics of Unix world that a CNC needs from time to time, today I chose to talk about the Vi editor. Its one of the most powerful editors on the console and certainly must know aspect of CNC administration.

Here are the few commands i know and have used over the years in Vi extensively. If you don't get it straight away just practice with patience and you will be rolling in no time

If you do not want to go the full path straight away just concentrate on the "basicest"  operations of creating, navigating , inserting and deleting in a Vi editor and you will be good for a while!! :)


General Startup
To use vi: vi filename
To exit vi and save changes: ZZ   or  :wq
To exit vi without saving changes: :q!
To enter vi command mode: [esc]

Counts
        A number preceding any vi command tells vi to repeat
that command that many times.


Cursor Movement

h       move left (backspace)

j       move down

k       move up

l       move right (spacebar)

[return]   move to the beginning of the next line

$       last column on the current line

0       move cursor to the first column on the
current line

^       move cursor to first nonblank column on the
current line

w       move to the beginning of the next word or
punctuation mark

W       move past the next space

b       move to the beginning of the previous word
or punctuation mark

B       move to the beginning of the previous word,
ignores punctuation

        e       end of next word or punctuation mark

        E       end of next word, ignoring punctuation

        H       move cursor to the top of the screen

        M       move cursor to the middle of the screen

        L       move cursor to the bottom of the screen


Screen Movement

       G        move to the last line in the file

       xG       move to line x

       z+       move current line to top of screen

       z        move current line to the middle of screen

       z-       move current line to the bottom of screen

       ^F       move forward one screen

       ^B       move backward one line

       ^D       move forward one half screen

       ^U       move backward one half screen

       ^R       redraw screen
( does not work with VT100 type terminals )

       ^L       redraw screen
( does not work with Televideo terminals )


Inserting

       r        replace character under cursor with next
character typed

       R        keep replacing character until [esc] is hit

       i        insert before cursor

       a        append after cursor

       A        append at end of line

       O        open line above cursor and enter append mode


Deleting

x       delete character under cursor

dd      delete line under cursor

        dw      delete word under cursor

        db      delete word before cursor


Copying Code

        yy      (yank)'copies' line which may then be put by
the p(put) command. Precede with a count for
multiple lines.


Put Command
        brings back previous deletion or yank of lines,
words, or characters

        P       bring back before cursor

        p       bring back after cursor

Find Commands

?       finds a word going backwards

/       finds a word going forwards

        f       finds a character on the line under the
cursor going forward

        F       finds a character on the line under the
cursor going backwards

        t       find a character on the current line going
forward and stop one character before it

T       find a character on the current line going
backward and stop one character before it

; repeat last f, F, t, T


Miscellaneous Commands

. repeat last command

u undoes last command issued

U undoes all commands on one line

xp deletes first character and inserts after
second (swap)

J join current line with the next line

^G display current line number

% if at one parenthesis, will jump to its mate

mx mark current line with character x

'x find line marked with character x

NOTE: Marks are internal and not written to the file.


Line Editor Mode
Any commands form the line editor ex can be issued
upon entering line mode.

To enter: type ':'

To exit: press[return] or [esc]


MOVING

:# move to line #

:$ move to last line of file







Thursday, November 10, 2011

Lets talk .profile

The .profile file in a Unix environment is a "know all" file. It resides under the /home/<userid> dir of the os and it's the first one to be executed whenever that particular user logs in. This is the file that creates the environment for the user and has all the shell options and environment variables defined.

Before we go into how JDE uses this file and why is it important for it, lets see what all it has first:

First and foremost comes PATH:

As the name suggests this is where the path to the dirs of the installed software go. Lets suppose we have a Unix user account MaxPayne. If MaxPayne has all the paths to the software or commands he uses defined in the .profile , he can run those command from anywhere once he logs in to the Unix shell.

Then comes the Editor.

More often than not, when we talk about default shell its the BASH shell and MaxPayne is no different. His shell is bash too and his .profile has Vi as an editor. Vi Editor is one of the most powerful command line editors that we have. Refer my post for the details about using Vi. If you need to change your editor all you need to do is specify it here in the .profile. For the record MaxPayne loves Vi.

Now we see PS1

PS1 defines what the command prompt looks like in the shell. Typically you will find the server name at the command prompt. But MaxPayne is smarter, he has included the $PWD in the PS1 definition so that he can see which dir he is in without ever needing to run pswd again!!

Last common entry is the Alias

Aliases are used to rename some commonly used commands. For example alias dir=ls will help a confused windows user to get the directory information he needs. Aliasing dir with ls tell the unix system to run ls every time MaxPayne types dir.

All the above are default entries in the .profile of any user. When it comes to a JDE Enterprise server what we see are the Oracle homes and the oneworld homes defined in the .profile. When the platform pack is run in the system it creates a .oneworld file in the user dir. This file tells the jde processes where all the JDE files are. We load this .oneworld in the .profile of the JDE file owner. Unless this is done services will not be able to start. So now when you see load libraries failing or path related issues coming up on restart, you know where to check. Majority of the times a corrupted .profile is the source of this.

This in brief is what .profile means to the JDE CNC. If you need any help configuring yours feel free to drop me a comment.