Shell Script

bash function

bash有幾個概念

  • echo string
  • return exit status(a number, not a string)
  • share variable (可用bash -n filename檢查語法)

Shell

  • 帶參數的函數
    MSG=$1 # 代表shell的第1個參數
foo() {
  msg=$1 # function的第一個參數
  echo "$msg"
}
    呼叫方式：foo "hello"
  • 日期/時間
    # 格式化
$(date +"%Y-%m-%d %H:%M:%S")
# 設定
date -s "20130122 02:02:03"
# 轉換 (Linux)
echo $(date +%F -d"1970-01-01 UTC 1372211942 seconds") => "2013-06-26"
echo $(date +%s -d"20130622") => "1371830400"
echo $(date +%s -d"20130622 09:01:02") => "1371862862"
echo $(date +%F -d@1427385600) => "2015-03-27"
  • $(指令), $((運算式))
    ver=$(username -r)
echo $ver
    結果：2618-128.e15
  • return value in function
    foo() {
  value=$1
  return "$value"
}
foo 456
status=$?
echo "status=$status"
    結果：status=456
  • 數字比較
    if [ "$status" -eq 456 ]; then
  ...
else
  ...
fi
其中：
-gt: >, greater than
-ge: >=
-lt: <, less than
-le: <=
-eq: ==
-nq: !=
  • 字串比較
    # 大小比較
if [[ "$s1" > "$s2" ]];
if [[ "$s1" < "$s2" ]];
if [[ "$s1" == "$s2" ]];
# contains
if [[ "$s1" == *"$s2"* ]];
  • Array (必須#!/bin/bash)
    # 走訪陣列
arr=(John Mary Peter) 或 arr=("John" "Mary" "Peter")
for x in ${arr[@]}; do
  echo "$x"
done
或
for ((i=0; i<${#arr[@]}; i++)); do
  echo "$x"
done

    # 給值
arr=[]
arr[0]=xxx
arr[1]=yyy
或
arr=()
arr+=(xxx)
arr+=(yyy)

    # range
for i in {1..5}; do
done
for i in {a..z}; do
done
  • 讀檔
    cat file.txt | while read line; do
  echo "$line"
done
    等效於
    while read line; do echo "$line"; done < file.txt
    ps: 此法因產生子shell process的關係，故有global/local變數問題
  • include
    source file.sh

  • md5

    md5sum file | awk '{print $1}'

  • 宣告整數

    declare -i x=100
# 若0080則視為8進位
# 10#0080才是10進位
  • return string
    get_ip() {
  echo "192.168.0.1"
}
ip="$(get_ip)"
echo "$ip"
    結果：192.168.0.1
  • sed
    # 變更字串 (s: substitute)
sed 's-\(username=\).*-\1welson-'
    代表由\(username=\).*變\1welson \1代表第1個()內的保存字
    # 變更檔案內容 (參數: -i)
sed -i 's/old/OLD/g' file.txt # g: global
sed -i 's/old/OLD/2' file.txt # 2: 前2個
sed -i 's/regex/d' file.txt # d: 刪某行
  • 讀取使用者輸入
    answer=""
read -e -p "y/n?" answer # 將結果存於answer

  • 字串處理

    str="/tmp/"
len=${#str} # 5
substring=${str:1:3} # 由index=1取3位
lastChar=${str:len-1:1} # 取最後一碼

    x=xyz.2.3.4.fc.i686
y=${x#*fc} # .i686
z=${y%.*} # 空值
其中
#: left strip
%: right strip

    s="key:v1:v2:v3"
echo "${s#*:}" # v1:v2:v3
echo "${s%:*}" # key:v1:v2

    # 轉大小寫
s="Hello"
echo "${s^^}" # HELLO
echo "${s,,}" # hello
# for Mac
echo $s | tr [:lower:][:upper]
echo $s | tr [:upper:][:lower]

    # cut
cut -c startIndex-stopIndex
## 應用在substring
s="abcd/doclib/user.xml"
echo $s | cut -c 1-8 => "abcd/doc"
echo $s | cut -c 5- => "/doclib/user.xml"
echo $s | cut -c 1- => 原字串
## 應用在smb.conf
samba="x:123:a,b,c"
echo $samba | cut -d':' -f2 => "123"
echo $samba | cut -d':' -f3 => "a,b,c"

  • switch-case

    case "$var" in
  abc | xyz)
      echo "case 1 or 2"
      ;;
  ijk)
      echo "case 3"
      ;;
  *)
      echo "defaults"
      ;;
esac
  • 印在同一行
    echo -ne "xxx\r"
  • 傳不定參數至script
    # A.sh
array=$*
for e in ${array[@]}; do
  echo $e
done
# 使用方式:
A.sh 123 abc xyz
    應用：實作 ./script.sh --param1=v1 --param2=v2
    #!/bin/bash
# 取出每一個參數
params=$*
for param in ${params[@]}; do
  echo "param=${param}, (k,v)=(${param%=*}, ${param#*=})"
done
#
# 或
#
# 逐一比對每個參數
while [ $# -gt 0 ]; do
  case "$1" in
      --param1=*)
          echo "param1 = ${1#*=}"
          ;;
      --param2=*)
          echo "param2 = ${1#*=}"
          ;;
      *)
          ;;
  esac
  shift
done

  • 傳送json至shell script (要加單引號)

    # json字串須加單引號
bash -x script.sh '[email protected]' '{"k1":"v1", "k2":"v2"}'
# 若不加單引號，則{}須跳脫
bash -x script.sh '[email protected]' \{"k1":"v1", "k2":"v2"\}

  • local variable

    str="global"
foo() {
  local str="local"
  echo "$str"
}
foo
echo "$str"

    結果

    local
global

  • tput控制stdout的style

    echo "$(tput bold) ABC" # 粗體ABC
echo "$(tput setaf i)" # 顏色: i={0(黑),1(紅),2(綠),3(黃),4(藍),5(Megenta),6(Cyan),7(白)}
echo "$(tput sgr0) ABC" # reset
echo "$(tput sgr 0 1)" # underline

  • Hash Table

    declare -A animals=(["k1"]="v1" ["k2"]="v2")
echo v1=${animals["k1"]} # 印出v1
echo keys=${!animals[@]} # 印出所有的keys. 可搭配 for key in ${!animals[@]}; do ... done
  • base64, big5
    # base64
echo "abc" | base64 # YWJjCg==
echo "YWJjCg==" | base64 -d
# big5
echo "abc" | iconv -f utf8 -t big5
# binary
echo "YWJjCg==" | xxd -b
  • 執行mysql指令
    /usr/bin/mysql -u username -p'password' -h $host <<EOFMYSQL
  create datebase if not exists $dbname;
EOFMYSQL
# 必須注意! 關鍵字`EOFMYSQL`不可縮排!
  • 查pid
    ps -ef | grep 'xxx' | grep -v grep | awk '{print $2}'

results matching ""

    No results matching ""