January 30, 2008

Add Password authentication to Apache Server

This is to add password authentication to Apache web server. The password file used is the Linux password file. By doing this, apache authentication is linked to linux authentication.

Of course because web authentication password is passed in clear, SSL/HTTPS should be used if security is of any concern.

download and install the Mod_Auth_External module
and the pwauth utility.

simply follow the instructions in INSTALL file.

One thing is to make sure the user id in pwauth config.h file is correct (corresponding to the "apache" user id).

January 17, 2008

SWFTOOLS Examples

Some good examples of swfc code, including a viewer for pdf

http://technoargia.free.fr/swftools/examples/viewer_home/viewer_home.html

January 16, 2008

Makefile Variables

A summary of the automatic variables. See Automatic Variables, for full information (taken from GNU Make Manual).
$@
The file name of the target.
$%
The target member name, when the target is an archive member.
$<
The name of the first prerequisite.
$?
The names of all the prerequisites that are newer than the target, with spaces between them. For prerequisites which are archive members, only the member named is used (see Archives).
$^
$+
The names of all the prerequisites, with spaces between them. For prerequisites which are archive members, only the member named is used (see Archives). The value of $^ omits duplicate prerequisites, while $+ retains them and preserves their order.
$*
The stem with which an implicit rule matches (see How Patterns Match).

January 8, 2008

BASH programming reference card

Appendix B. Reference Cards

The following reference cards provide a useful summary of certain scripting concepts. The foregoing text treats these matters in more depth, as well as giving usage examples.

Table B-1. Special Shell Variables

VariableMeaning
$0Filename of script
$1Positional parameter #1
$2 - $9Positional parameters #2 - #9
${10}Positional parameter #10
$#Number of positional parameters
"$*"All the positional parameters (as a single word) *
"$@"All the positional parameters (as separate strings)
${#*}Number of command line parameters passed to script
${#@}Number of command line parameters passed to script
$?Return value
$$Process ID (PID) of script
$-Flags passed to script (using set)
$_Last argument of previous command
$!Process ID (PID) of last job run in background

* Must be quoted, otherwise it defaults to "$@".

Table B-2. TEST Operators: Binary Comparison

OperatorMeaning-----OperatorMeaning
Arithmetic Comparison String Comparison
-eqEqual to =Equal to
==Equal to
-neNot equal to !=Not equal to
-ltLess than \<Less than (ASCII) *
-leLess than or equal to
-gtGreater than \>Greater than (ASCII) *
-geGreater than or equal to
-zString is empty
-nString is not empty
Arithmetic Comparisonwithin double parentheses (( ... ))
>Greater than
>=Greater than or equal to
<Less than
<=Less than or equal to

* If within a double-bracket [[ ... ]] test construct, then no escape \ is needed.

Table B-3. TEST Operators: Files

OperatorTests Whether-----OperatorTests Whether
-eFile exists -sFile is not zero size
-fFile is a regular file
-dFile is a directory -rFile has read permission
-hFile is a symbolic link -wFile has write permission
-LFile is a symbolic link -xFile has execute permission
-bFile is a block device
-cFile is a character device -gsgid flag set
-pFile is a pipe -usuid flag set
-SFile is a socket -k"sticky bit" set
-tFile is associated with a terminal
-NFile modified since it was last read F1 -nt F2File F1 is newer than F2 *
-OYou own the file F1 -ot F2File F1 is older than F2 *
-GGroup id of file same as yours F1 -ef F2Files F1 and F2 are hard links to the same file *
!"NOT" (reverses sense of above tests)

* Binary operator (requires two operands).

Table B-4. Parameter Substitution and Expansion

ExpressionMeaning
${var}Value of var, same as $var
${var-DEFAULT}If var not set, evaluate expression as $DEFAULT *
${var:-DEFAULT}If var not set or is empty, evaluate expression as $DEFAULT *
${var=DEFAULT}If var not set, evaluate expression as $DEFAULT *
${var:=DEFAULT}If var not set, evaluate expression as $DEFAULT *
${var+OTHER}If var set, evaluate expression as $OTHER, otherwise as null string
${var:+OTHER}If var set, evaluate expression as $OTHER, otherwise as null string
${var?ERR_MSG}If var not set, print $ERR_MSG *
${var:?ERR_MSG}If var not set, print $ERR_MSG *
${!varprefix*}Matches all previously declared variables beginning with varprefix
${!varprefix@}Matches all previously declared variables beginning with varprefix

* Of course if var is set, evaluate the expression as $var.

Table B-5. String Operations

ExpressionMeaning
${#string}Length of $string
${string:position}Extract substring from $string at $position
${string:position:length}Extract $length characters substring from $string at $position
${string#substring}Strip shortest match of $substring from front of $string
${string##substring}Strip longest match of $substring from front of $string
${string%substring}Strip shortest match of $substring from back of $string
${string%%substring}Strip longest match of $substring from back of $string
${string/substring/replacement}Replace first match of $substring with $replacement
${string//substring/replacement}Replace all matches of $substring with $replacement
${string/#substring/replacement}If $substring matches front end of $string, substitute $replacement for $substring
${string/%substring/replacement}If $substring matches back end of $string, substitute $replacement for $substring
expr match "$string" '$substring'Length of matching $substring* at beginning of $string
expr "$string" : '$substring'Length of matching $substring* at beginning of $string
expr index "$string" $substringNumerical position in $string of first character in $substring that matches
expr substr $string $position $lengthExtract $length characters from $string starting at $position
expr match "$string" '\($substring\)'Extract $substring* at beginning of $string
expr "$string" : '\($substring\)'Extract $substring* at beginning of $string
expr match "$string" '.*\($substring\)'Extract $substring* at end of $string
expr "$string" : '.*\($substring\)'Extract $substring* at end of $string

* Where $substring is a regular expression.

Table B-6. Miscellaneous Constructs

ExpressionInterpretation
Brackets
if [ CONDITION ]Test construct
if [[ CONDITION ]]Extended test construct
Array[1]=element1Array initialization
[a-z]Range of characters within a Regular Expression
Curly Brackets
${variable}Parameter substitution
${!variable}Indirect variable reference
{ command1; command2; . . . commandN; }Block of code
{string1,string2,string3,...}Brace expansion
{a..z}Extended brace expansion
{}Text replacement, after find and xargs
Parentheses
( command1; command2 )Command group executed within a subshell
Array=(element1 element2 element3)Array initialization
result=$(COMMAND)Execute command in subshell and assign result to variable
>(COMMAND)Process substitution
<(COMMAND)Process substitution
Double Parentheses
(( var = 78 ))Integer arithmetic
var=$(( 20 + 5 ))Integer arithmetic, with variable assignment
(( var++ ))C-style variable increment
(( var-- ))C-style variable decrement
(( var0 = var1<98?9:21>C-style trinary operation
Quoting
"$variable""Weak" quoting
'string'"Strong" quoting
Back Quotes
result=`COMMAND`Execute command in subshell and assign result to variable
From http://tldp.org/LDP/abs/html/refcards.html#AEN20071