Arch Linux cpupower Missing Library Temporary Fix

If you are experiencing the issue described at https://bbs.archlinux.org/viewtopic.php?id=213404 (copied here for your convenience--courtesy of bartbkr):

After a recent upgrade, when I attempt to use cpupower, I get the following
message:

    cpupower: /usr/lib/libpci.so.3: verion `LIBPCI_3.5' not found (required by cpupower)

I haven't changed any of the setting for cpupower recently and everything was
running smoothly before. Now I can't query the cpu settings any longer.

$ ls /usr/lib/libpci.so*
        /usr/lib/libpci.so
        /usr/lib/libpci.so.3
        /usr/lib/libpci.so.3.4.1

Then, the temporary solution is to downgrade cpupower to version 4.6.1. Follow the general downgrade guide at https://wiki.archlinux.org/index.php/Downgrading_packages. For comparison sake, this is the log of failed cpupower at start-up in my machine:

root@jeez /var/cache/pacman/pkg
 # systemctl status cpupower.service
— cpupower.service - Apply cpupower configuration
   Loaded: loaded (/usr/lib/systemd/system/cpupower.service; enabled; vendor preset: disabled)
   Active: failed (Result: exit-code) since Mon 2016-06-06 22:07:38 SGT; 44min ago
  Process: 328 ExecStart=/usr/lib/systemd/scripts/cpupower (code=exited, status=1/FAILURE)
 Main PID: 328 (code=exited, status=1/FAILURE)

Jun 06 22:07:37 jeez systemd[1]: Starting Apply cpupower configuration...
Jun 06 22:07:37 jeez cpupower[328]: cpupower: /usr/lib/libpci.so.3: version `LIBPCI_3.5'
Jun 06 22:07:38 jeez systemd[1]: cpupower.service: Main process exited, code=exited, sta
Jun 06 22:07:38 jeez systemd[1]: Failed to start Apply cpupower configuration.
Jun 06 22:07:38 jeez systemd[1]: cpupower.service: Unit entered failed state.
Jun 06 22:07:38 jeez systemd[1]: cpupower.service: Failed with result 'exit-code'.

This is the excerpt the steps that I did to fix the issue via package downgrade:

root@jeez /var/cache/pacman/pkg
 # pacman -U cpupower-4.6-1-x86_64.pkg.tar.xz
loading packages...
warning: downgrading package cpupower (4.6-2 => 4.6-1)
resolving dependencies...
looking for conflicting packages...

Packages (1) cpupower-4.6-1

Total Installed Size:   0.41 MiB
Net Upgrade Size:      -0.10 MiB

:: Proceed with installation? [Y/n] Y
(1/1) checking keys in keyring                            [###############################] 100%
(1/1) checking package integrity                          [###############################] 100%
(1/1) loading package files                               [###############################] 100%
(1/1) checking for file conflicts                         [###############################] 100%
(1/1) checking available disk space                       [###############################] 100%
:: Processing package changes...
(1/1) downgrading cpupower                                [###############################] 100%
:: Running post-transaction hooks...
(1/1) Updating manpage index...
root@jeez /var/cache/pacman/pkg
 # systemctl restart cpupower.service
root@jeez /var/cache/pacman/pkg
 # journalctl -xe
Jun 06 22:51:51 jeez systemd[1]: Starting Apply cpupower configuration...
-- Subject: Unit cpupower.service has begun start-up
-- Defined-By: systemd
-- Support: http://lists.freedesktop.org/mailman/listinfo/systemd-devel
--
-- Unit cpupower.service has begun starting up.
Jun 06 22:51:52 jeez systemd[1]: Started Apply cpupower configuration.
-- Subject: Unit cpupower.service has finished start-up
-- Defined-By: systemd
-- Support: http://lists.freedesktop.org/mailman/listinfo/systemd-devel
--
-- Unit cpupower.service has finished starting up.
--
-- The start-up result is done.
pinczakko@jeez Mon Jun 06 10:52:07pm
~/ systemctl status cpupower.service
— cpupower.service - Apply cpupower configuration
   Loaded: loaded (/usr/lib/systemd/system/cpupower.service; enabled; vendor preset: disabled)
   Active: active (exited) since Mon 2016-06-06 22:51:52 SGT; 26s ago
  Process: 2672 ExecStart=/usr/lib/systemd/scripts/cpupower (code=exited, status=0/SUCCESS)
 Main PID: 2672 (code=exited, status=0/SUCCESS)

Jun 06 22:51:51 jeez systemd[1]: Starting Apply cpupower configuration...
Jun 06 22:51:52 jeez systemd[1]: Started Apply cpupower configuration.

As you see in the shell log above, after downgrading cpupower to version 4.6.1, everything went back to normal. This is only temporary fix until libpci 3.5 promoted from testing to stable. We can go back to cpupower version 4.6.2 by then.

Using DBX Debugger on AIX -- How to pass program arguments to DBX

DBX is the default debugger in IBM AIX OS. This debugger's user interface is rather unusual compared to other debugger. It is a command line debugger just like GNU GDB. But, it has a different philosophy. The user guide for DBX is at: https://www.ibm.com/support/knowledgecenter/ssw_aix_61/com.ibm.aix.cmds2/dbx.htm. The user guide is exhaustive to be read all at once. I recommend you to focus on your goal, i.e. debugging requirements and read the user guide to suite the requirements.

Let's start with a basic requirements:

• You have a command line program 
• The program has several arguments that must be passed at startup time.

Now, let's look at the steps to fulfill the requirements above. Let's start with DBX philosophy. The DBX philosophy is as follows:

1. Running dbx without any arguments in the shell only starts the debugging environment, nothing more, nothing less.
2. Running dbx with only the executable (program) file name will load the executable into memory but doesn't run the program. This step also doesn't pass any argument(s) to the program.  
3. DBX has the so-called "subcommands" which are "commands" that you can type in the DBX debugging environment to instruct the debugger to do something. Another way to pass subcommand to DBX is via a text file known as "command file". A command file contains subcommand and the parameters/arguments required by the subcommand.

The gist of the philosophy is: useful thing can be done mostly via DBX subcommands. The following diagram illustrates this philosophy.

Figure 1 IBM AIX DBX debugger principle of working

The DBX Command Line Interface (CLI) is similar to GNU GDB. Therefore, I'm not going to explain it here. I'll proceed to DBX Scripting Interface. The scripting interface is invoked via DBX's "-c" flag. This is the excerpt from DBX user guide:

-c CommandFile

Runs the dbx subcommands in the file before reading from standard input. The specified file in the $HOME directory is processed first; then the file in the current directory is processed. The command file in the current directory overrides the command file in the $HOME directory. If the specified file does not exist in either the $HOME directory or the current directory, a warning message is displayed. The source subcommand can be used once the dbx program is started.

I'll show you how to use -c flag to pass your program arguments at the start of a DBX debugging session. The first thing to do before we can use -c flag is to prepare the Command File. If you just want to pass your program arguments, then the contents of the command file is simply the run subcommand and your program arguments. Below is an example of a valid Command File. Let's name the command file as my_cmd.

run -a 10.10.10.254 -p 8000 -n 2  

In the command file above, the program (to be debugged) arguments starts at -a, the run statement in the beginning refers to DBX run subcommand. The following diagram shows this:

Figure 2 Using run subcommand in your command file

This is the verbatim explanation for run subcommand  from DBX user guide:

run Subcommand

run [ Arguments ] [ <File ] [ >File ] [ > >File ] [ 2>File ] [ 2> >File ] [ >&File ] [ > >&File ]

The run subcommand starts the object file. The Arguments are passed as command-line arguments.

Flags

Item	Description
<File	Redirects input so that input is received fromFile.
>File	Redirects output to File.
2>File	Redirects standard error to File.
> >File	Appends redirected output to File.
2> >File	Appends redirected standard error to File.
>&File	Redirects output and standard error to File.
> >&File	Appends output and standard error to File.

Example

To run the application with the arguments blue and 12, enter:

run blue 12




Therefore, to start DBX debugger to use my_cmd command file above, we enter this in the shell:

$ dbx -c my_cmd [your_program_name]

The -c flag instruct dbx to use my_cmd as the command file, after that you just need to enter your program executable name. Anyway, after dbx parses the command file, it runs your program as if you type run subcommand in a DBX debugging session.

That's it. I hope this post helps those who just started using DBX in AIX or other AIX-like environment.

Blank Character is Not Null Character

Perhaps, it is partly because I'm not a native English speaker and partly because I forgot that the devil is in the details that I inadvertently wrote code that supposed to initialize a variable with blank characters with null characters.

Blank characters refer to whitespace character (https://en.wikipedia.org/wiki/Whitespace_character), not the null character (https://en.wikipedia.org/wiki/Null_character). In many cases, acceptable blank character for program input is space, which has a value of 20h in ASCII and 40h in EBCDIC. Well, this is not obvious for me at first until I'm debugging some code in an EBCDIC environment. 

So, next time you read an API documentation that says *BLANK*, it doesn't refer to NULL ('\0') character, but it refers to one of the whitespace character which in many cases refer to SPACE (' ').

As a bonus, these are some usable character conversion tables:

http://www.simotime.com/asc2ebc1.htm

https://shop.alterlinks.com/ascii-table/ascii-ebcdic-us.php

http://www.astrodigital.org/digital/ebcdic.html (this one explicitly states SPACE character as BLANK)

[How-to] Copy Contents of Tmux Pane to File

There are many cases where you might want to copy part of (or the entire) contents of a tmux pane into file for further usage. This post explains how to that. Before we proceed, you need to be aware that my tmux key binding is probably different from yours, see: http://darmawan-salihun.blogspot.co.id/2015/02/zsh-tmux-configuration-for-arch-linux.html. I'm using vi mode-keys.

The steps to copy contents of a tmux pane are as follows:

1. Enter copy mode. The key combo to enter copy mode depends on your tmux configuration, but the principle never change: press your tmux prefix key combo--in my case, this is Ctrl+A--and then press your tmux copy mode key-in my case the key is Escape. If you look at my tmux configuration file linked above, I should press: Ctrl+A, then Escape to enter tmux copy mode. 
2. Select the text that you want to copy. I'm using the v key to select the text because that's how my tmux key binding is configured (~/.tmux.conf: bind -t vi-copy 'v' begin-selection). This is how it looks like once I have selected some text in copy mode with vi-like keys (the selected text is in yellow background):
   

   

   tmux copy mode
3. Copy the selected text into tmux buffer. I'm using y (yank) key to select the text because that's how my tmux key binding is configured (~/.tmux.conf: bind -t vi-copy 'y' copy-selection). Now the selected text is in tmux buffer.

You can "save" contents of the tmux buffer to a file with this command:

$ tmux save-buffer -b [the_buffer_yo_want_to_save] -a [name_of_the_file_you_want_to_append_the_buffer_to]

If you want to just overwrite the contents of the "target" file with the tmux buffer contents, you can omit the -a flag. You can select your "source" tmux buffer before saving the tmux buffer contents by using the command completion key in your shell (in my case TAB -- I'm using zsh). Tmux buffer possibly contains more than one buffer if you previously "copy" something into the buffer, either inadvertently or on-purpose. This is how tmux buffer looks like in my shell as I'm trying to save one of its entries:

Tmux "copy buffer" number 0 to number 10

Anyway, you can also bind keys to the tmux save buffer command in order to make the text available for GUI application as in my tmux.conf shown in the link above. This is the configuration snippet (I'm using icccm clipboard for that):

# extra commands for interacting with the ICCCM clipboard
bind C-c run "tmux save-buffer - | xclip -i -sel clipboard"
bind C-v run "tmux set-buffer \"$(xclip -o -sel clipboard)\"; tmux paste-buffer"

That's it. I hope the explanation is clear enough because there are many explanation on the web that's not quite well-suited for newbie.