rdoc documentation: usage(*args) Display usage information ... put something like this on top of your script: # == Synopsis # Blah blah blah. # ... method to display it def output_usage RDoc::usage('usa... bind it to the '-h' option via optionparser opts.on('-h', '--help') { output_help } ... source http://blog.toddwerth.com/entries/5

In Android.mk , you can define LOCAL_JARJAR_RULES like this: LOCAL_JARJAR_RULES := $(LOCAL_PATH)/jarjar-rules.t... and in jarjar-rules.txt define a rule like this: rule org.bouncycastle.** com.android.@0 The build will change all org.bouncycastle to com.android.org.bouncycastle . Therefore, in your classes which are dependent on the library produced, the import statements should look like: import com.android.org.bouncycastle... Help for the jarjar utility (in prebuilt/common/jarjar/ ): $ java -jar jarjar-1.0rc8.jar Jar Jar Links - ...

It's quite easy for Perl to open a pipe and read from it: $file = "nospace.txt"; open(IN, "cat $file |") ... But the code breaks when the file name contains a space: # This does not work! $file = "yes space.txt"; ... On Windows, these don't work either: # This does not work! $file = "yes space.txt"; ... You need to use a technique called Safe Pipe Opens : $file = "yes space.txt"; $prog = "cat"; ...

Variable Meaning $_ The default or implicit variable. @_ Within a subroutine the array @_ contains the parameters passed to that subroutine. $a, $b Special package variables when using sort() $<digit> Contains the subpattern from the corresponding set of capturing parentheses from the last pattern match, not counting patterns matched in nested blocks that have been exited already. $. Current line number for the last filehandle accessed. $/ The input record separator, newline by default. $| If set to nonzero, forces a flush right away and after every write or print on the currently selected output channel. Default is 0 (regardless of whether the channel is really buffered by the system or not; $| tells you only whether you've asked Perl explicitly to flush after...

Variable Description $0 The name of the ruby script file $* The command line arguments $$ Ruby interpreter's process ID $? Exit status of last executed child process $_ String last read by gets $. Line number last read by interpreter $! Last error message $@ Location of error $& String last matched by regexp $~ The last regexp match, as an array of subexpressions $n the nth subexpression in the last match (same as $~ ) $= Sase-insensitivity flag $/ Input record separator $\ Output record separator

Use the diff command to find the difference between two files. It takes two arguments: 2 files, 1 file and 1 directory, or 2 directories. diff file1 file2 # display the differe...

To loop through an envionment variable: @echo off set a=1 2 3 for %%i in (%a%) d... To loop through the command line arguments: @echo off for %%i in (%*) do echo %%i