Shell String Operators test

引用:

#!/bin/bash
# Author : BlueSilence  E-MAIL: liumengxin@126.com
#This Shell script will tell you how to  use String Operators :
#${varname:-word}，${varname:=word},${varnameffset}
#${varnamemessage},${varname:+word},${varnameffset:length}
#${variable#pattern} ${variable##pattern} ${variable%pattern}
#${variable%%pattern} ${variable/pattern/string}
#${variable//pattern/string}
# enjoy !
############# Set color commands, used via echo -e##########

purple="\\033[0;35m"
green="\\033[0;32m"
light_blue="\\033[1;34m"
NORMAL="\\033[0;39m"
###### ${varnamemessage} test ###################
selectVAR ()
{
FREE='VAR:free'
EXIT="VAR:freeAndAbortTheScript"
OPTIONS="null  $FREE  $EXIT linux "
select opt in $OPTIONS
do
    if [ "$opt" = "$EXIT" ]
    then
        echo 'excellent ! you are right ! ^_^ '
        return
    else
        echo 'wrong ! hurry up ! '
        return
     fi
done

}

selectVARII ()
{
FREE='VAR:free'
EXIT="VAR:freeAndAbortTheScript"
OPTIONS="null  $FREE  $EXIT linux "
select opt in $OPTIONS
do
    if [ "$opt" = "null" ]  || [ "$opt" = "linux" ]
    then
        echo 'excellent ! you are right ! ^_^ '
        return
    else
        echo 'wrong ! hurry up ! '
        return
     fi
done
}

##############explain menu#############################
explainSubstitution ()
{
PLUS='varname:+word'
MINUS='varname:-word'
EQUAL='varname:=word'
MESSAGE='varnamemessage'
OFFSET='varnameffset:length'
COLON='aboutColon('
OPTIONS=" $PLUS $MINUS $EQUAL $MESSAGE $OFFSET $COLON Return "
select opt in $OPTIONS
do
        case $opt in
                $PLUS)
                echo "$PLUS................"
                varname:+word
                ;;
                $MINUS)
                echo "$MINUS................ "
                varname:-word
                ;;
                $EQUAL)
                echo "$EQUAL................"
                varname:=word
                ;;
                $MESSAGE)
                echo "$MESSAGE..............."
                varnamemessage
                ;;
                $OFFSET)
                echo "$OFFSET................."
                varnameffset:length
                ;;
                $COLON)
                  echo "$COLON.................."
                  colon
                  ;;
                Return)
                  echo "Good Bye ! ^_^ "
                  echo "press enter to continue .........."
                  return
                  ;;
             esac
done
}
explainPattern ()
{
P1='variable#pattern'
P2='variable##pattern'
P3='variable%pattern'
P4='variable%%pattern'
P5='variable//pattern/string'
P6='aboutRemember'
OPTIONS="$P1 $P2 $P3 $P4 $P5 $P6 Return "
select opt in $OPTIONS
do
        case $opt in
                $P1)
                echo "$P1 ........."
                variable_pattern
                ;;
                $P2)
                echo "$P2 ........."
                variable_patternII
                ;;
                $P3)
                echo "$P3 ........."
                variable%pattern
                ;;
                $P4)
                echo "$P4 ........"
                variable%%pattern
                ;;
                $P5)
                echo "$P5 ........."
                variable//pattern/string
                ;;
                $P6)
                echo "$P6 ........."
                aboutRemember
                ;;
                Return)
                echo "Good Bye ! ^_^ "
                echo "press enter to continue ........"
                return
                ;;
        esac
done
}

explainALL ()
{
OPTIONS="SubstitutionOperatorsExplain PatternMatchExplain ReturnMenu"
        select opt in $OPTIONS
do
        case $opt in
                SubstitutionOperatorsExplain)
                echo "please wait ......."
                sleep 1
                explainSubstitution
                ;;
                PatternMatchExplain)
                echo "please wait ........"
                sleep 1
                explainPattern
                ;;
                ReturnMenu)
                echo "enjoy ! ^_^ "
                echo "press enter to continue ........."
                return
                  ;;
          esac
done
}

##############EXPLICATION  Content####################################
colon ()
{
    echo -e -n $NORMAL
    echo "The colon (  : "
    echo "The colon ( in all but the last of these operators is actually "
    echo "optional. If the colon is omitted, then change  exists and isn't "
    echo "null to \"exists\" in each definition, i.e., the operator tests  "
    echo "for existence only."
}

varname:-word ()
{
        echo -e -n $green
        echo -n '${varname:-word}  :    '
        echo "If varname exists and isn't null, return its value;"
        echo " otherwise return word."
        echo -n 'Purpose  :   '
        echo 'Returning a default value if the variable is undefined.'

}

varname:=word ()
{
        echo -e -n $light_blue
        echo -n ' ${varname:=word }  :   '
        echo 'If varname exists and isn't null, return its value;
        echo "otherwise set it to word and then return its value."
        echo " Positional and special parameters cannot be assigned this way."
        echo -n 'Purpose   :   '
        echo 'Setting a variable to a default value if it is undefined.'


}

varnamemessage ()
{
        echo -e -n $green
        echo -n '${varnamemessage} :   '
        echo "If varname exists and isn't null, return its value; "
        echo "otherwise print varname: followed by message "
        echo "and abort the current"
        echo "command or script (non-interactive shells only). Omitting message"
        echo 'produces the default message parameter null or not set.'
        echo -n 'Purpose :   '
        echo 'Catching errors that result from variables being undefined.'

}
varname:+word ()
{
      echo -e -n $purple
      echo -n '${varname:+word}  :   '
      echo "If varname exists and isn't null, return word; "
      echo "otherwise return null "
      echo -n 'Purpose  :    '
      echo 'Testing for the existence of a variable.'

}

varnameffset:length ()
{
         echo -e -n $purple
         echo  '${varnameffset:length}  :   '
         echo 'Performs substring expansion.a It returns the substring of '
         echo ' $varname starting at offset and up to length characters.'
         echo 'The first character in $varname is position 0. If length is '
         echo 'omitted, the substring starts at offset and continues to the '
         echo 'end of $varname. If offset is less than 0 then the position is '
         echo ' taken from the end of $varname. If varname is @, the length is '
         echo 'the number of positional parameters starting at parameter offset.'
         echo 'Purpose :  '
         echo "Returning parts of a string (substrings or slices)"
}

variable_pattern ()
{
        echo -e -n $purple
        echo -n '${variable#pattern}  :  '
        echo "If the pattern matches the beginning of the variable's value"
        echo "delete the shortest part that matches and return the rest"
}
variable_patternII ()
{
        echo -e -n $light_blue
        echo -n '${variable##pattern}  :  '
        echo "If the pattern matches the beginning of the variable's value"
        echo "delete the longest part that matches and return the rest."
}
variable%pattern ()
{
        echo -e -n $green
        echo -n '${variable%pattern}  :  '
        echo "If the pattern matches the end of the variable's value"
        echo "delete the shortest part that matches and return the rest"
}
variable%%pattern ()
{
        echo -e -n $NORMAL
        echo -n '${variable%%pattern}  :  '
        echo "If the pattern matches the end of the variable's value "
        echo "delete the longest part that matches and return the rest"
}
variable//pattern/string ()
{
        echo -e -n $light_blue
        echo  '${variable//pattern/string} : '
        echo "The longest match to pattern in variable is replaced by string"
        echo '${variable/pattern/string}: only the first match is replaced '
        echo '${variable//pattern/string}:  all matches are replaced '
        echo "If the pattern is begins with a # "
        echo "it must match at the start of the variable"
        echo "If it begins with a %, it must match with the end of the variable"
        echo "If string is null, the matches are deleted"
        echo "If variable is @ or * ,  the operation is applied to each "
        echo " positional parameter in turn and the expansion is "
        echo "the resultant list"
}
aboutRemember ()
{
        echo -e -n $NORMAL
        echo "These can be hard to remember, so here's a handy mnemonic device:"
        echo "# matches the front because number signs precede numbers"
        echo "% matches the rear because percent signs follow numbers"
        echo "When searching for the longest match "
        echo "use ## (because ## is longer than #)"
        echo " When searching for the shortest match, use # "
        echo "See, not that hard to remember at all! ^_^"
}



###########Substitution Operators test############################################
###${varname:-word}  ${varname:=word} ${varnamemessage} ${varname:+word}
###${varnameffset}  ${varnameffset:length}

substitution ()
{
echo -e -n $NORMAL
echo "1: set VAR=linux ........."
VAR=linux
sleep 1
echo -n 'ok... STR=${VAR:-free} $STR is :  '
read input
STR=${VAR:-free}
if [ "$input" = "$STR" ]
then
        echo 'good! you are right ! ^_^'
else
        echo 'wrong! hurry up ! '
fi
echo -n '$VAR is : '
read inputVAR
if [ "$inputVAR" = "$VAR" ]
then
        echo 'excellent ! so clever ! ^_^ '
else
        echo 'wrong ! hurry up ! '
fi

echo  "2: set VAR=   (null)......."
VAR=
sleep 1
echo -n 'ok..... STR=${VAR:-free} $STR  is :  '
read input
STR=${VAR:-free}
if [ "$input" = "$STR" ]
then
        echo  'good ! you are right... ^_^'
else
        echo 'wrong ! hurry up ! '

fi
echo -n '$VAR is : '
read inputVAR
if [ "$inputVAR" = "$VAR" ]
then
        echo 'excellent ! so clever  ! ^_^ '
else
        echo 'wrong ! hurry up '
fi

echo "3: set  VAR=    ......."
VAR=
sleep 1
echo -n 'ok..... STR=${VAR-free}  $STR  is :  '
read input
STR=${VAR-free}
if [ "$input" = "$STR" ]
then
        echo 'good ! you are right ^_^ '
else
        echo 'wrong ! hurry up ! '

fi
echo -n '$VAR is : '
read inputVAR
if [ "$inputVAR" = "$VAR" ]
then
        echo 'excellent ! so clever ! ^_^'
else
        echo 'wrong ! hurry up ! '
fi

echo 'unset  VAR  ..........'
unset VAR
sleep 1
echo -n 'ok........  STR=${VAR-free}   $STR is : '
read input
STR=${VAR-free}
if [ "$input" = "$STR" ]
then
        echo 'good ! you are right ! ^_^ '
else
        echo 'wrong! hurry up ! '
fi
echo -n '$VAR is : '
read inputVAR
if [ "$inputVAR" = "$VAR" ]
then
        echo 'excellent ! so clever  ! ^_^ '
else
        echo 'wrong ! hurry up ! '
fi


echo "4: set VAR=linux ......"
VAR=linux
sleep 1
echo -n 'ok....  STR=${VAR:=free} $STR  is :  '
read input
STR=${VAR:=free}
if [ "$input" = "$STR" ]
then
        echo 'good ! you are right ! ^_^'
else
        echo 'wrong ! hurry up ! :('
fi
echo -n "the VAR value is : "
read inputVar
if [ "$inputVar" = "$VAR" ]
then
        echo 'excellent ! so clever  !^_^ '
else
        echo 'wrong ! hurry up ! :('
fi
echo "5: set VAR=     ........ ."
VAR=
sleep 1
echo -n 'ok....  STR=${VAR:=free}  $STR  is : '
read input
STR=${VAR:=free}
if [ "$input" = "$STR" ]
then
        echo 'good ! you are right ! ^_^'
else
        echo 'wrong ! hurry up ! :( '

fi
echo -n '$VAR is : '
read inputVAR
if [ "$inputVAR" = "$VAR" ]
then
        echo 'excellent ! so clever  ! ^_^'
else
        echo 'wrong ! hurry up ! :( '
fi

echo "6: set VAR=    ............"
VAR=
sleep 1
echo -n 'ok... STR=${VAR=free} $STR  is  '
read input
STR=${VAR=free}
if [ "$input" = "$STR" ]
then
        echo 'good ! you are right ! ^_^ '
else
        echo 'wrong ! hurry up ! :('
fi
echo -n "The VAR value is :  "
read inputVAR
if [ "$inputVAR" = "$VAR" ]
then
        echo 'excellent ! so clever  ! ^_^'
else
        echo 'wrong ! hurry up ! :('
fi

echo 'unset VAR  ..........'
unset VAR
sleep 1
echo -n 'ok........  STR=${VAR=free}   $STR is : '
read input
STR=${VAR=free}
if [ "$input" = "$STR" ]
then
        echo 'good ! you are right ! ^_^ '
else
        echo 'wrong! hurry up ! :( '
fi
echo -n '$VAR is : '
read inputVAR
if [ "$inputVAR" = "$VAR" ]
then
        echo 'excellent ! so clever  ! ^_^ '
else
        echo 'wrong ! hurry up ! :( '
fi


echo "7: set VAR=linux ..........."
VAR=linux
sleep 1
echo -n 'ok....  STR=${VAR:+free}  $STR  is '
read input
STR=${VAR:+free}
if [ "$input" = "$STR" ]
then
        echo 'good ! you are right ! ^_^'
else
        echo 'wrong ! hurry up ! :('
fi
echo -n "The VAR value is : "
read inputVAR
if [ "$inputVAR" = "$VAR" ]
then
        echo 'excellent ! so clever  ! ^_^'
else
        echo 'wrong ! hurry up ! :('
fi
echo "8: set VAR=   ..........."
VAR=
sleep 1
echo -n 'ok..... STR=${VAR:+free}  $STR  is '
read input
STR=${VAR:+free}
if [ "$input" = "$STR" ]
then
        echo 'good ! you are right ! ^_^'
else
        echo 'wrong ! hurry up ! :( '
fi
echo -n "The VAR value is :"
read inputVAR
if [ "$inputVAR" = "$VAR" ]
then
        echo 'excellent ! so clever  ! ^_^'
else
        echo 'wrong ! hurry up :( '
fi
echo "9: set VAR=   .........."
VAR=
sleep 1
echo -n 'ok..... STR=${VAR+free} $STR  is : '
read input
STR=${VAR+free}
if [ "$input" = "$STR" ]
then
        echo 'good ! you are right ! ^_^'
else
        echo 'wrong ! hurry up ! :('
fi
echo -n "The VAR value is : "
read inputVAR
if [ "$inputVAR" = "$VAR" ]
then
        echo 'excellent ! so clever  ! ^_^ '
else
        echo 'wrong ! hurry up ! :( '
fi

echo 'unset VAR  ..........'
unset VAR
sleep 1
echo -n 'ok........  STR=${VAR+free}   $STR is : '
read input
STR=${VAR+free}
if [ "$input" = "$STR" ]
then
        echo 'good ! you are right ! ^_^ '
else
        echo 'wrong! hurry up ! :( '
fi
echo -n '$VAR is : '
read inputVAR
if [ "$inputVAR" = "$VAR" ]
then
        echo 'excellent ! so clever  ! ^_^ '
else
        echo 'wrong ! hurry up ! :( '
fi

echo "10 : set VAR=linux ........"
VAR=linux
sleep 1
echo  'ok......  STR=${VARfree}   $STR is :'
selectVARII

echo "11 : set VAR=    ........."
VAR=
sleep 1
echo  'ok........  STR=${VARfree}  $STR is : '

selectVAR

echo "12 : set VAR=   .............."
VAR=
sleep 1
echo 'ok......... STR=${VAR?free}  $STR is : '
selectVARII


echo "13 :set VAR=Ilovelinux ......."
VAR=Ilovelinux
sleep 1
echo -n 'ok....  STR=${VAR:1:4} $STR is : '
read input
STR=${VAR:1:4}
if [ "$input" = "$STR" ]
then
        echo 'good ! you are right ! ^_^'
else
        echo 'wrong ! hurry up ! :( '
fi

echo -n "The VAR value is : "
read inputVAR
if [ "$inputVAR" = "$VAR" ]
then
        echo 'excellent ! so clever  ! ^_^ '
else
        echo 'wrong ! hurry up ! :('
fi

echo "14 :set VAR=Ilovelinux ........"
VAR=Ilovelinux
sleep 1
echo -n 'ok.... STR=${VAR:4:5}  $STR  is : '
read input
STR=${VAR:4:5}
if [ "$input" = "$STR" ]
then
        echo 'excellent ! so clever !  ^_^'
else
        echo 'wrong ! hurry up ! :('
fi
echo "15 : set VAR=Ilovelinux ........."
VAR=Ilovelinux
sleep 1
echo -n 'ok......   STR=${VAR:1}   $STR  is : '
read input
STR=${VAR:1}
if [ "$input" = "$STR" ]
then
        echo 'good ! you are right ! ^_^ '
else
        echo 'wrong ! hurry up ! :( '
fi
echo -n '$VAR  is  : '
read inputVAR
if [ "$inputVAR" = "$VAR" ]
then
        echo 'excellent ! so clever ! ^_^ '
else
        echo 'wrong ! hurry up ! :( '
fi
echo "16 : set VAR=Ilovelinux ............."
VAR=Ilovelinux
sleep 1
echo -n 'ok.........  STR=${VAR:5}    $STR  is : '
read input
STR=${VAR:5}
if [ "$input" = "$STR" ]
then
        echo 'excellent ! so clever ! ^_^ '
else
        echo 'wrong ! hurry up ! :( '
fi
sleep 1
echo "complete............................."
echo "Are you crazy ? * ^_^*  "
echo "Explication : .........please select : "
explainSubstitution
}

##########pattenrns_match test###############################
####${variable#pattern} ${variable##pattern} ${variable%pattern}####
#####${variable%%pattern} ${variable/pattern/string} ${variable//pattern/string}

patterns_match ()
{
echo -e -n $NORMAL
echo "1: set VAR=/usr/bin/startkde  ........."
VAR=/usr/bin/startkde
sleep 1
echo -n 'ok....... STR=${VAR##*/}  $STR is : '
STR=${VAR##*/}
read inputSTR
if [ "$inputSTR" = "$STR" ]
then
         echo 'good ! you are right !  basename ? ^_^ '
else
         echo 'wrong ! hurry up ! :( '
fi

echo -n ' $VAR is  : '
read inputVAR
if [ "$inputVAR" = "$VAR" ]
then
        echo 'excellent ! so clever ! ^_^ '
else
        echo 'wrong ! hurry up ! :( '
fi

echo "2 : set VAR=/tmp/backup.tar.gz .........."
sleep 1
VAR=/tmp/backup.tar.gz
echo -n 'ok.....  STR=${VAR#*.}  $STR  is  : '
STR=${VAR#*.}
read inputSTR
if [ "$inputSTR" = "$STR" ]
then
        echo 'good ! you are right ! ^_^ '
else
        echo 'wrong ! hurry up ! :( '
fi

echo "3 : set VAR=/opt/gcc/bin/gcc ........"
VAR=/opt/gcc/bin/gcc
sleep 1
echo -n 'ok......  STR=${VAR%/*}  $STR  is  : '
STR=${VAR%/*}
read inputSTR
if [ "$inputSTR" = "$STR" ]
then
        echo 'good ! you are right ! dirname ? ^_^ '
else
        echo 'wrong ! hurry up ! :( '
fi
echo -n ' $VAR is : '
read inputVAR
if [ "$inputVAR" = "$VAR" ]
then
        echo 'excellent ! so clever ! ^_^ '
else
        echo 'wrong ! hurry up ! :( '
fi

echo "4 : set VAR=/tmp/backup.tar.gz   ........ "
VAR=/tmp/backup.tar.gz
sleep 1
echo -n 'ok......  STR=${VAR%%.*}   $STR  is  :  '
STR=${VAR%%.*}
read inputSTR
if [ "$inputSTR" = "$STR" ]
then
        echo 'good ! you are right ! ^_^ '
else
        echo 'wrong ! hurry up ! :( '
fi

echo "5 : set VAR=alicece  ........."
VAR=alicece
sleep 1
echo -n 'ok.......  STR=${VAR%%ce}  $STR  is : '
STR=${VAR%%ce}
read inputSTR
if [ "$inputSTR" = "$STR" ]
then
        echo 'excellent ! so clever ! because ce is exact match  ^_^ '
else
        echo 'wrong ! hurry up ! because ce is exact match so alice is right:( '
fi

echo "6 : set VAR=/bin:/usr/bin:/sbin ......... "
VAR=/bin:/usr/bin:/sbin
sleep 1
echo -n 'ok........  STR=${VAR//:/|}  $STR  is : '
STR=${VAR//:/|}
read inputSTR
if [ "$inputSTR" = "$STR" ]
then
        echo 'good ! you are right ! ^_^ '
else
        echo 'wrong ! hurry up ! :( '
fi
echo -n ' $VAR is  :  '
read inputVAR
if [ "$inputVAR" = "$VAR" ]
then
        echo 'excellent ! so clever ! ^_^ '
else
        echo 'wrong ! hurry up ! :( '
fi

echo "7 : set VAR=/tmp/backup.tar.gz  ........."
VAR=/tmp/backup.tar.gz
sleep 1
echo -n 'ok........ STR=${VAR/./..}  $STR is :  '
STR=${VAR/./..}
read inputSTR
if [ "$inputSTR" = "$STR"  ]
then
        echo 'good ! you are right ! ^_^ '
else
        echo 'wrong ! hurry up ! :( '
fi
echo "complete......................."
echo "EXPLANATION : "
sleep 1
explainPattern
}

###########main menu##############################
choice ()
{

    local OPTIONS=" Explanation SubstitutionOperatorsTest PatternMatchTest EXIT"
        select opt in $OPTIONS
        do
                case $opt in

                        Explanation)
                        echo "please wait......"
                        sleep 1
                        explainALL
                        ;;
                         SubstitutionOperatorsTest)
                         echo "please wait......"
                         sleep 1
                         substitution
                         ;;
                         PatternMatchTest)
                         echo "please wait......"
                         sleep 1
                         patterns_match
                         ;;
                         EXIT)
                         echo -e -n $NORMAL
                         echo "EXIT........"
                         exit
                         ;;
                 esac
        done

}

###########start here###############
echo -e -n $light_blue
echo "This Shell script will tell you how to use String Operators "
echo -n "String operators allow you to manipulate values of variables in various"
echo -n " useful ways without having to write full-blown programs or resort to "
echo -n "external UNIX utilities"
echo "In particular, string operators let you do the following:"
echo "*  Ensure that variables exist (i.e., are defined and have non-null values)"
echo "*  Set default values for variables"
echo "*  Catch errors that result from variables not being set"
echo "*  Remove portions of variables' values that match patterns"
sleep 2
echo "Are you Ready ?  Take a breath   three seconds ......... "
sleep 3
echo "ok  let\`s go ! ^_^"

echo "Now , What do you want ?"
   choice

#end

引用:

* ${varname%%pattern} if pattern matches the end of the value of varname then delete the longest part that matches and return the rest