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Function Samples

ip 驗證

# Test an IP address for validity:
# Usage:
#      valid_ip IP_ADDRESS
#      if [[ $? -eq 0 ]]; then echo good; else echo bad; fi
#   OR
#      if valid_ip IP_ADDRESS; then echo good; else echo bad; fi
#
function is_ip()
{
    local  ip=$1
    local  stat=1

    if [[ $ip =~ ^[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}$ ]]; then
        OIFS=$IFS
        IFS='.'
        ip=($ip)
        IFS=$OIFS
        [[ ${ip[0]} -le 255 && ${ip[1]} -le 255 \
            && ${ip[2]} -le 255 && ${ip[3]} -le 255 ]]
        stat=$?
    fi
    return $stat
}

分割線(自動調整寬度)

CL () { 
WORDS=$@; termwidth="$(tput cols)"; padding="$(printf '%0.1s' ={1..500})"; printf '%*.*s %s %*.*s\n' 0 "$(((termwidth-2-${#WORDS})/2))" "$padding" "$WORDS" 0 "$(((termwidth-1-${#WORDS})/2))" "$padding"; 
}

CL "This is Seperator Line"

大小寫轉換

ToUpper() {
    echo $1 | tr "[:lower:]" "[:upper:]"
}

ToLower() {
    echo $1 tr "[:upper:]"} "[:lower:]"
}

URL 字串編碼

function urlencode() {
    local data
    if [[ $# != 1 ]]; then
        echo "Error: No string to urlencode"
        return 1
    fi
    data="$(curl -s -o /dev/null -w %{url_effective} --get --data-urlencode "$1" "")"
    if [[ $? != 3 ]]; then
        echo "Unexpected error" 1>&2
    else
        echo "${data##/?}"
    fi
    return 0
}

urlencode "$1"

function urldecode() {
    # urldecode <string>

    local url_encoded="${1//+/ }"
    printf '%b' "${url_encoded//%/\\x}"
}

函數回傳字串

  • https://linuxhint.com/return-string-bash-functions/
  • https://www.linuxjournal.com/content/return-values-bash-functions

Example-1: Using Global Variable

function F1()
{
    retval='I like programming'
}

retval='I hate programming'
echo $retval
F1
echo $retval

Example-2: Using Function Command

function F2()
{
    local  retval='Using BASH Function'
    echo "$retval"
}

getval=$(F2)   
echo $getval

Example-3: Using Variable

function F3()
{
    local arg1=$1
    
    if [[ $arg1 != "" ]]; 
    then
        retval="BASH function with variable"
    else
        echo "No Argument"
    fi
}

getval1="Bash Function"
F3 $getval1
echo $retval
getval2=$(F3)
echo $getval2

is_root
用途：檢查是否以 root 帳號執行

is_root()
{
	current_user="`id`"
	case "$current_user" in
		uid=0\(root\)*)
		;;
		*)
			echo "$0: You must have root privileges in order to install ${product_name}"
			echo "su as root and try again"
			echo
			exit 1
		;;
	esac
}

check_os
用途：檢查 OS 版本

check_os()
{
	if [ -f /etc/redhat-release ];then
		rhel=`grep "^Red Hat Enterprise Linux" /etc/redhat-release`
		centos=`grep "^CentOS" /etc/redhat-release`
		
		release=`cat /etc/redhat-release | cut -d'.' -f1 | awk '{print $NF}'`
		
		if [ ! -z "${rhel}" ];then
			sys="rhel"
		fi

		if [ ! -z "${centos}" ];then
			sys="rhel"
		fi
	fi

	if [ -z "${sys}" -o -z "${release}" ];then
		echo "Can not determine Linux distribution."
		exit 127
	fi
			
	if [ -f /proc/vz/veinfo ];then
	# we are under Virtuozzo
		virtuozzo=1
	else
		virtuozzo=0
	fi
	
	if [ "${VNDEBUG}" ];then
		debugrpm='--rpmverbosity=debug'
	else
		debugrpm=''
	fi
}

IsRunning
用途：檢查自身程序是否已經執行中，如果有，程序立即跳離，可避免同一個 script 重複被執行。

IsRunning() {
    if [ ! -e $script_pid ];then
        RUNCOUNT=0
    else
        RUNPID=$(cat $script_pid)
        RUNCOUNT=$(ps -fp $RUNPID | grep -c `basename $0`)
    fi
    #echo $RUNCOUNT

    if [ $RUNCOUNT -eq 0 ];then
        echo $$ > $script_pid
        return 1  # return False
    else
        return 0  # return True
    fi
}

script_pid="/tmp/$(basename $0).$(whoami).pid"
# Check if the program is already running.
if IsRunning
then
    echo "Abort: The program is already running!"
    exit 1
fi

getopts 指令參數

Usage() {
    echo "Usage: $0 [-t <TEXT-Message>] [-n <phone-number>]";
    echo "For example: $0 -t \"Hello, SuperMan\" -n \"085713 457199\" "
}

while getopts ":t:n:" o; do
    case "$o" in
        t)
            t=$OPTARG
            ;;
        n)
            n=$OPTARG
            ;;
        \?)
            echo "Invalid option: -$OPTARG"
            Usage
            exit 1
            ;;
        :)
            echo "Option -$OPTARG requires an argument !"
            Usage
            exit 1
            ;;
    esac
done

if [ $OPTIND -ne 5 ]; then
    echo "Invalid options entered !"
    Usage
    exit 1
fi

Pause 暫停
用法: pause

可用於程式開發及偵錯

pause()
{

	local force_pause=$1

	if [ -z $force_pause ]; then
		if test $NONINTERACTIVE; then
			return 0
		fi
	else
		shift
	fi

	[ $# -ne 0 ] && echo -e $* >&2
	echo -e "Press [Enter] to continue...\c " >&2
	read tmp
	return 0
}

Log 訊息

log() {  # classic logger
    local prefix="[$(date +%Y/%m/%d\ %H:%M:%S)]: "
    echo "${prefix} $@" >&2
} 

log "INFO" "a message"

Error 錯誤訊息
用途：輸出錯誤訊息

error()
{
	echo -e "Error: $*!" >&2
	return 0
}

die()
{
	echo
	echo "ERROR: $*"
	echo
	echo "Check the error reason, fix and try again."
	echo "You are welcome to open a support ticket at https://help.4psa.com!"
	echo
	rm -f ${repolocal} local$$
	rm -f /var/lock/subsys/vninstaller
	exit 1
}

check_deps()
{
	which yum >/dev/null 2>&1
	if [ $? -gt 0 ];then
		echo "yum binary can not be found."
		die "It's not in the system PATH or in a standard location."
	fi
	
	which ifconfig >/dev/null 2>&1
    if [ $? -gt 0 ];then
		yum -y install net-tools >/dev/null 2>&1
		if [ $? -gt 0 ];then	
			echo "ifconfig binary can not be found and package net-tools could not be installed."
			die "It's not in the system PATH or in a standard location."
		fi
	fi
}

詢問 Yes/No
用法: getyn "Would you like to install WANPIPE now? [y]"

$NONINTERACTIVE  如果程式執行時，不想讓 user 做任何的輸入時，可以為 1
NONINTERACTIVE=1 ，或者 = 空白，以顯示相關的提示訊息

prompt()
{
	if test $NONINTERACTIVE; then
		return 0
	fi

	echo -ne "$*" >&2
	read CMD rest
	return 0
}

getyn()
{
	if test $NONINTERACTIVE; then
		return 0
	fi

	while prompt "$* (y/n) "
	do	case $CMD in
		[yY])	return 0
			;;
		[nN])	return 1
			;;
		*)	echo -e "\nPlease answer y or n" >&2
			;;
		esac
	done
}
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