Effective Coding on Unix

Updated 2006-10-04

In this article, I will explain how I code on unix.

Use a unix Computer

Store your source code and compile it on a unix computer. It will be your development server. I recommend using a popular version of Linux: Gentoo, Debian, or Ubuntu. I don't think that Cygwin makes a good development platform.

Avoid sysadmin work. Use a computer that somebody else manages. If you're a university student then get a shell account on the university's system. If you're a UIC CS student then use oscar.cs.uic.edu.

Use PuTTY

If you already have a Linux workstation or a Mac with OS X then you can run ssh from a terminal to connect to your development server. On Windows, use the free SSH client, PuTTY. Follow these instructions to install it properly on Windows XP™:

Go to the PuTTY Download page. Download the "Windows-style installer". At the time of this writing, it is called putty-0.58-installer.exe.
Run the installer. Install with the default options. This puts the PuTTY files into C:\Program Files\PuTTY
The pscp.exe program must appear on the path for it to be useful. Configure the PATH environment variable:
1. Right-click on My Computer and choose Properties. The System Properties dialog box will appear.
2. Click the Advanced tab.
3. Click the Environment Variables button at the bottom. The Environment Variables dialog box will appear.
4. Under System variables, scroll down and select Path.
5. Click the Edit button. The Edit System Variable dialog box will appear.
6. Click in the box labeled Variable value: and press the End button on your keyboard to go to the end of the text.
7. Type ;C:\Program Files\PuTTY; at the end of the text. The semicolons are important!
8. Click OK to save changes to the Path variable.
9. Click OK to close the Environment Variables dialog box.
10. Click OK to close the System Properties dialog box.
Make a shortcut to your development server, oscar.cs.uic.edu:
1. Open My Computer and navigate to C:\Program Files\PuTTY.
2. Press Alt-F-W-S to open the Create Shortcut wizard.
3. Type putty oscar.cs.uic.edu and hit Enter.
4. Type oscar.cs.uic.edu as the name of the shortcut and hit Enter to finish creating the shortcut.
5. Press Alt-F-I to add it to the Start Menu.

PuTTY comes with good default settings. Commands and settings are available by clicking the icon in the upper-left corner of the window, just left of the title bar. I like to increase the Font size and maximize the window.

You can get full-screen mode with ALT-Enter. This makes the PuTTY window take up the entire screen. It looks just like your computer is the development server. Turn on the ALT-Enter shortcut key like this:

Click the tiny icon in the upper-left corner of the PuTTY window
Choose Change Settings
In the tree on the left, select Window / Behavior
Check the box next to "Full screen on Alt-Enter"
Click the Apply button

To make your changes stick in the program, you need to save over PuTTY's default settings:

Click the tiny icon in the upper-left corner of the PuTTY window
Session should already be selected on the left side
"Default Settings" should already be selected on the right side
Click the Save button
Click the Apply button

Use Tab-Completion

All decent unix shells can interpret the tab key to complete a partially typed filename. With tab-completion, one can manage files very effectively. It is much faster than using a using a mouse and graphical file manager.

Single tab to complete - complete match appears with a space after
partial match - no space
after partial match, double tab prints out candidates
Tcsh
Bash - on by default
Name your files so tab completion is easy.
all lowercase

Use Screen

Do all of your development with one terminal. Use screen to create virtual terminals and switch betwen them using the keyboard command. There is a huge advantage to keeping your hands on the keyboard all the time.

Run screen with screen -R
Disconnect the screen session and return to the shell: ^a d (it means hold down CTRL and press A, then press D)
Your programs will remain in the background, waiting for you to run screen -R again.
If you close PuTTY or get disconnected you can just log in again and reconnect.
Create a screen: ^a c
Each screen gets a number, starting at 0, up to 9.
Switch to screen 2: ^a 2
Switch back to previous screen: ^a ^a
Close a screen: ^a k or exit the shell running in it
Renumber current screen to be 9: ^a : number <space> 9 <enter>
Always use the same screen numbers for each program that you use. For example:
- Screen 0: intial screen, use for emacs (or vim)
- Screen 1: shell for running your program
- Screen 2: shell for looking up man pages
- Screen 9: irssi IRC client for consulting the gurus on Freenode
Add an extra window: ^a S (that is a capital S)
Switch focus to next window: ^a <tab>
Remove the focused window: ^a X
Zoom the focused window: ^a Q
Accidentally pressing ^a s (lower case S) sends xoff to the current window. This tells the program to stop updating the screen. You can fix this by sending xon: ^a q (lower case q)
Help: ^a ?
Enter the long form of a screen command after typing ^a :
You can also put these commands in your ~/.screenrc file so they run each time you start screen. A useful command is escape ^\ which changes the command prefix from ^a to ^\. There are many commands. Read about them in the man page: man screen

Use Emacs

Read Effective Emacs (local copy).

Customize your ~/.emacs file. I have incorporated most of the suggestions in Effective Emacs into my .emacs file.

Cancel any command with Esc Esc Esc
Quit with ^x ^c
Clipboard
- Mark (start of selection)
- Kill (cut)
- Kill line
- Yank (paste)
Panes
- Switch Panes ^x o
- One Pane ^x 1
- Two Panes ^x 2
- …
Buffers
- Switch to buffer by name ^x b
- Show list of buffers ^x ^b
- Kill buffer ^x k
- Open or create a file ^x ^f (use tab completion on filename!)
- Save current buffer ^x ^s
- Save all buffers ^x s (prompts for each one, ! saves all)
Command prompt Alt-x (supports tab-completion of command names!)
- help
- global-font-lock-mode (turns on syntax high lighting)
- put commands in ~/.emacs, with parameters, surrounded by parentheses: (global-font-lock-mode t)
Searching
- Incremental search ^s
- Replace Esc %

Write a Good Makefile

Use the makefile to build, clean, and test. For interactive programs, add command line options that bypass the interactive prompts, so you can test your program without interacting with it. Make many tests: test1, test2, test, etc. Make tests that should succeed and others that should cause your program to report errors. Make clean should remove core, *.o, all temporary files created by tests, and the program's executable.

Learn to Read Manpages

They can be tough for an inexperienced person to understand. Read the entire manpage of every library function call that is used by your program. Also take a look at man pages listed in the SEE ALSO section. The manpage open(2) is for the open in section 2 of the manual. Read it with man 2 open. If your unix system views manpages with more then change it to less.

Keep Source Code Organized

Be organized. Don't mix source code and other files. Put test data files in a test/ subdirectory. What is suitable for the source code directory: c, cpp, h, makefile, readme, INSTALL, COPYING, any data files required by your program.

Use tar

tar czvf project.f.tar.gz project/

tar xzvf project.f.tar.gz

Keep backups of your source code directory: a, b, c, …, z.

Use pscp to copy the backups to your workstation

Prevent Programming Errors

Use assert
Fix bugs immediately
Test after every bug fix and edit

Write proper function headers before writing the function. Example:

/* concat - joins the proclists together into a new list
   @param head the head of the new list, or NULL if empty
   @param tail the tail of the new list, or NULL if empty
   @return the new list, or NULL if empty
*/

Avoid deep indentation by using functions. Make all code have a maximum of 3 levels of indentation. Example:

int foo (int x)
{
  if (100>x)
    {
      if (0==x)
        {
	  /* let's indent only this far and use functions */
	  return bar(x);
	}
    }
  else return x;
}

Put constant first in comparisons: 0==x, 100>=x, -5>x
Learn to use const
Learn about variable scope and lifetime
Learn about pointers
Learn C-strings really really well

TODO

Things to add to this tutorial:

Run your development system in a virtual machine such as VirtualPC, Xen, etc.
Use subversion, cvs, or darcs to keep your source and config under revision control.
Back up your repository with rsync
Use ssh keys and Pageant to avoid typing your password
Make sections for C, C++, Java, Erlang, Python
Include example Makfile
Write about removing distractions
Write about taking breaks to let your subconscious mind solve problems
Write about reduced productivity late at night (like now)

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