awk -F\, '{gsub(/^[ \t]+/, "", $2); gsub(/[ \t]+$/, "", $2); print $2 ":"}'

awk 'gsub(/^[0-9]([0-9])?[\\.、、，,]( )?/, "", $2);' a.txt

set time = 12:34:56
set hr = `echo $time | awk '{split($0,a,":" ); print a[1]}'` # = 12
set hms = `echo $time | awk '{split($0,a,":" ); for (i=1; i<=3; i++) print a[i]}'`

if [[ $1x == "ab"x ]]; then
    echo "you had enter ab"
elif [[ $1x == "cd"x ]]; then
    echo "you had enter cd"
else
    echo "you had enter unexpected word"
fi

sh test.sh > log 2>&1   # 错误输出也重定向到1里面

if [[ ! -f $bizdate.done ]] ; then exit 0; fi   # 如果不存在done文件, 退出
if [[ -f $bizdate.done ]] ; then echo "exits"; fi   # 如果存在done文件

if [ ! -d "/data/" ];then
	mkdir /data
else
	echo "文件夹已经存在"
fi

#使用read命令读取一行数据
while read myline
do
echo "LINE:"$myline
done < datafile.txt

find ./ -mtime +2 -name \*.done | xargs /bin/rm -rf;  # 删除两天之前的done文件
　
-mtime +n : 列出在n天之前（不含n天本身）被更改过内容的文件名
-mtime -n : 列出在n天之内（含n天本身）被更改过内容的文件名

for ((i = 0; i <= $max_days - 1; i++)); do
    d=`date +%Y%m%d -d "$i day ago $DATE"`
    if [[ $? -ne 0 ]]; then continue; fi
done

比较两个字符串是否相等的办法是：

if [ "$test"x = "test"x ]; then
    这里的关键有几点：
    1 使用单个等号
    2 注意到等号两边各有一个空格：这是unix shell的要求
    3 注意到"$test"x最后的x，这是特意安排的，因为当$test为空的时候，上面的表达式就变成了x = testx，显然是不相等的。而如果没有这个x，表达式就会报错：[: =: unary operator expected

source ~/.bashrc
source ~/.bash_profile
LC_ALL=C

alias echot="echo -e [`date "+%Y-%m-%d %T"`]"

if [[ $# -ne 3 ]] ; then
    echo "<Usage>: sh getRandom.sh inFile randomNum outFile"
    exit 1
fi

function random()
{
    local min=$1
    let max=$2-$1
    local num=`date +%N`
    let local retnum=10#$num%10#$max+10#$min
    echo $retnum;
}

# 1: get the line number
lnum=`wc -l $1 | cut -d " " -f 1`
echot "[Info] File Name: "$1
echot "[Info] Lines Num is: "$lnum

# 2: get the random indexs first
echot "[Info] Begin Get Random Nums:"$2
declare -a randomNums

for((index=0; index<$2;))
do
    curNum=`random 0 $lnum`
    if [[ ${randomNums[$curNum]} -ne 1 ]] ; then
        randomNums[$curNum]=1
        let index=index+1
    fi
done
echot "[Info] End Get Random Nums:"$2

#3：read all the lines from input file, but didn't save in the memory
index=0
getNum=0
declare -a lines

echot "[Info] Begin Read Lines"
while read line
do
    if [[ ${randomNums[$index]} -eq 1 ]] ; then
        lines[$getNum]=$line
        let getNum=getNum+1
    fi
    if [[ $getNum -eq $2 ]] ; then
        break
    fi
    let index=index+1
done < $1
echot "[Info] End Read Lines"


#4：wirte choosed lines into file
cat /dev/null > $3
for i in "${!lines[@]}" ; do
    echo "${lines[$i]}" >> $3
done