bash's parameter expansion

[bash's parameter expansion]

　#: find first from left, remove-left

　##: find last from left, remove left

　%: find first from right, remove right

　%%: find last from right, remove right

　example 1:

 parameter     result
 -----------   ------------------------------
 ${NAME}       polish.ostrich.racing.champion
 ${NAME#*.}           ostrich.racing.champion
 ${NAME##*.}                         champion
 ${NAME%%.*}   polish
 ${NAME%.*}    polish.ostrich.racing

　example 2:

 parameter     result
 -----------   --------------------------------------------------------
 ${FILE}       /usr/share/java-1.4.-sun/demo/applets/Clock/Clock.class
 ${FILE#*/}     usr/share/java-1.4.-sun/demo/applets/Clock/Clock.class
 ${FILE##*/}                                                Clock.class
 ${FILE%%/*}
 ${FILE%/*}    /usr/share/java-1.4.2-sun/demo/applets/Clock

string slice:

${string::}   # The third character of string (, ,  = third)
${string:}     # The string starting from the second character
                # Note: this is equivalent to ${string#?}
${string%?}     # The string with its last character removed.
${string: -}   # The last character of string
${string:(-)}  # The last character of string, alternate syntax
                # Note: string:- means something entirely different; see below.

${file%.mp3}    # The filename without the .mp3 extension
                # Very useful in loops of the form: for file in *.mp3; do ...
${file%.*}      # The filename without its last extension
${file%%.*}     # The filename without all of its extensions
${file##*.}     # The extension only, assuming there is one. If not, will expand to ${file}

toupper (^) and tolower (,):

 # string='hello, World!'
 parameter     result
 -----------   --------------------------------------------------------
 ${string^}    Hello, World! # First character to uppercase
 ${string^^}   HELLO, WORLD! # All characters to uppercase
 ${string,}    hello, World! # First character to lowercase
 ${string,,}   hello, world! # All characters to lowercase

assignment:

 ${var-word}             # if var is defined, use var; otherwise, "word"
 ${var+word}             # if var is defined, use "word"; otherwise, nothing
 ${var=word}             # if var is defined, use var; otherwise, use "word" AND...
                         #   also assign "word" to var
 ${var?error}            # if var is defined, use var; otherwise print "error" and exit

参考: http://bash.cumulonim.biz/BashFAQ(2f)073.html