工作中經常需要用Shell寫一些腳本用于測試，但是每次寫shell，我都痛苦不已，因為shell的語法形式太雜亂，各種括號，各種$XX，搞得我每次寫完腳本，都得花大把時間解決語法格式錯誤。
為了解決這個問題，提高寫shell的效率，我把一些shell常用的demo，總結出來，方便我以及各位讀者查閱哈！

字符串連接

sh_strcat() {
    #method 1
    local str="strcat"
    local str2="helo"
    echo "strcat method1: ${str} ${str2}"

    #method 2
    echo "strcat method2:" ${str} ${str2}
}

獲取字符串長度

sh_strlen() {
    local str="strlen"
    echo "strlen: ${#str}"
}

截取字符串

sh_substr() {
    local substr="hello Meizu!"
    echo -n "substr:"
    #起始下標：截取個數
    echo ${substr:0:5}
    echo ${substr:6:5}
}

if-else語句格式

sh_if_else() {
    local min=10
    local max=10
    
    # -gt -lt -le -ge

    #if [ ${min} -lt ${max} ]; then
    if ((${min} < ${max})); then
        echo "min < max"

    #elif [ ${min} -gt ${max} ]; then
    elif ((${min} > ${max})); then
        echo "min > max"

    else
        echo "min = max"
    fi
}

for語句格式

sh_for_ctrl_fmt() {
    echo "sh_for_ctrl_format:"
    #for((i=0; i<10; i++)); do
    for i in `seq 10`; do
        echo $i
    done
}

while語句格式

sh_while_fmt() {
    local var=10
    while ((${var} > 0)); do
        var=$((var-1))
        echo $var
    done
}

執行shell命令，并將結果賦給變量

sh_set_val_according2exec_res() {
    var=$(date)
    echo $var
}

echo -e 開啟轉義字符

sh_echo_e() {
    echo "echo -e:"
    echo -e "OK \\\\\\\\t END"         #horizonal tab
    echo -e "OK \\\\\\\\n END"         # 換行
    echo -e "OK ccc \\\\\\\\c ccc END" # 不再產生輸出
    echo -e "OK \\\\\\\\b END"         #執行退格鍵
    echo -e "OK \\\\\\\\v END \\\\\\\\v eee"  #vertical tab
}

執行命令，拋棄所有輸出

sh_exec_throw_output() {
    ls >/dev/null 2>&1
}

$各種符號意義*

sh_dollar_means() {
    echo "查看shell本身進程ID \\\\\\\\$\\\\\\\\$: $$"
    echo "最后運行的后臺PID \\\\\\\\$!: $!"
    echo "最后運行命令的結束碼 \\\\\\\\$?: $?"
    echo "所有參數列表1 \\\\\\\\$*: $*"
    echo "所有參數列表2 \\\\\\\\$@: $@"
    echo "參數個數 \\\\\\\\$\\\\\\\\#: $#"
    echo "當前腳本文件名 \\\\\\\\$0: $0"
}

四則運算

sh_operator() {
    echo "sh_operator:"
    local num1=10
    local num2=10

    #res=`expr 2 \\\\\\\\* ${num1}`
    #echo ${res}

    local result_add=$((${num1} + ${num2}))
    echo "add: "$result_add

    local result_minus=$((${num1} - ${num2}))
    echo "minus: "$result_minus

    local result_multi=$((${num1} * ${num2}))
    echo "multi: "$result_multi

    local result_divide=$((${num1} / ${num2}))
    echo "divide: "$result_divide

    local result_mod=$((${num1} % ${num2}))
    echo "mod: "$result_mod

    #######################################

    let result_add++
    echo "result_add++: "${result_add}

    let ++result_add
    echo "++result_add: "${result_add}

    let result_add+=5
    echo "result_add+=5: "${result_add}
    
    let result_add--
    echo "result_add--: "${result_add}

    let --result_add
    echo "--result_add: "${result_add}

    let result_add-=5
    echo "result_add-=5: "${result_add}
}

sh_random

sh_random() {
    local random_num=`awk 'BEGIN{srand();print int(rand()*1000)}'`
    echo "random num:  ${random_num}"
}

EOF INPUT

sh_EOF_INPUT() {
    ncat $ip 6600 << EOF
seekid $position $random_num
EOF
}

strcmp && ||

# -a  ==> 邏輯與
# -o  ==> 邏輯或
#    !  ==> 邏輯非
sh_strcmp() {
    echo "sh_strcmp:"
    local str1='y'
    local str2='z'
    #if (( "x${str1}" == "xy" && "x${str2}" == "xz" ));then
    #if [ "x${str1}" == "xy" -a "x${str2}" == "xz" ];then
    if [[ "x${str1}" == "xy" && "x${str2}" == "xz" ]];then
        echo "sh_strcmp: && success"
    else
        echo "sh_strcmp: && failed"
    fi

    local flag=0
    #if [ ! ${flag} == 0 ]; then
    if (( ! ${flag} == 0 )); then
        echo "! success"
    else
        echo "! failed"
    fi

    #if (( -d "/etc/zsh" && -e /etc/zsh/newuser.zshrc.recommended )); then
    if [ -d "/etc/zsh" -a -e /etc/zsh/newuser.zshrc.recommended ]; then
        echo "exist"
    else
        echo "not exist"
    fi
}

sh_switch_case

sh_switch_case() {
    echo "sh_switch_case:"

    case "$1" in
        start)          echo "case $1";;
        stop)           echo "case $1";;
        install)        echo "case $1";;
        remove)         echo "case $1";;
        upgrade)        echo "case $1";;
    esac
}

輸出pwd

sh_print_pwd() {
    echo "sh_print_pwd:"
    dirname=$(cd "$(dirname "$0")";pwd)
    echo "dirname: "${dirname}
}

awk抓取html

sh_awk_spider_html() {
    echo "sh_awk_spider_html:"
    awk -F'<div class="content"|/ul>' '{for(i=1;i<=NF;i++){if($i~/class="play-img"/){print $i}}}' \\\\\\\\
        ${bt_spider_web_path}plug_xunbo.html|grep -a "h2"|grep -a "${bt_detail_url}" |tail -1 > ${bt_spider_log}xunbo_${kind}_classify.log

    awk -F'<a|/>' '{for(i=1;i<=NF;i++){if($i~/alt/){print $i}}}' ${bt_spider_log}xunbo_${kind}_classify.log  > ${bt_spider_log}classify_${kind}_info.log

    awk -F'[""]' '{print $4}'  ${bt_spider_log}classify_${kind}_info.log > ${bt_spider_log}bt_${kind}_detail_link.log 
    awk -F'[""]' '{print $6}'  ${bt_spider_log}classify_${kind}_info.log > ${bt_spider_log}bt_${kind}_name.log 
    awk -F'[""]' '{print $10}' ${bt_spider_log}classify_${kind}_info.log > ${bt_spider_log}bt_${kind}_pic.log 
}

sed基本使用

#查詢hello關鍵字，打印相應行 
sed -n '/hello/p' cron.txt   

#刪除含hello的行，輸出到屏幕（原文件沒刪除）
sed  '/hello/d' cron.txt  

#跟上一句的區別：直接修改原文件
sed -i '/hello/d' cron.txt  

#移除空白行：
sed -i '/^$/d' file

#在包含hello關鍵字的指定行前加#號，注釋該行：
sed -i '/hello/s/^/#/g' /etc/crontabs/root 

#取消#號，取消注釋：
sed -i '/hello/s/^#//' /etc/crontabs/root

如果想了解更多awk和sed這兩條命令，請參考陳皓大神寫的相關文章~

• sed
• awk