Linux shell常用命令

1. 获取系统线程总数

   pstree -p | wc -l

2. 获取指定名称进程id

   以mysql为例
   [root@localhost ~]# ps -elf | grep mysql |grep -v grep | awk '{print$4}' | xargs
   31622 31821

3. 批量杀死指定名称进程

   以mysql为例
   kill `ps -elf | grep mysql |grep -v grep | awk '{print$4}' | xargs`

4. shell将命令执行结果分割为数组

   [root@localhost dongsongz]# cat testarray.sh 
   #!/bin/bash
   
   processes=`ps -elf | grep tcpreplay | grep -v grep | awk '{print$4}' | xargs`
   echo $processes
   process_array=($processes)
   for id in ${process_array[@]};do
       echo $id
   done
   
   [root@localhost dongsongz]# ./testarray.sh 
   11424 11461 11521
   11424
   11461
   11521
   

5. shell指定分割符分割字符串为数组

   [root@localhost dongsongz]# cat testarray2.sh 
   #!/bin/bash
   
   str=`cat ./test.txt`
   echo $str
   IFS=","
   array=($str)
   for i in ${array[@]};do
     echo $i
   done
   [root@localhost dongsongz]# ./testarray2.sh 
   hello,from,test!
   hello
   from
   test!
   

   shell可以通过IFS指定分割符（默认是空格）来分割字符串为数组

6. shell按C风格for循环遍历数组

   [root@k8s-node2 debug]# cat for.sh 
   #!/bin/bash
   
   teststring='a,b,c,d,e,f,g'
   #指定,分割字符串
   IFS=","
   array=($teststring)
   
   #${#array[@]}表示数组array元素个数
   for((i=0;i<${#array[@]};i++))
   do
       #${array[$i]}表示第i个元素内容
       echo ${array[$i]}
   done
   
   [root@k8s-node2 debug]# ./for.sh 
   a
   b
   c
   d
   e
   f
   g
   

   ${!array[@]}或${!array[*]}，可以返回数组的成员序号，即哪些位置是有值的。

7. shell解析命令行参数

   [root@localhost debug]# cat cmdarg.sh 
   #!/bin/bash
   
   usage="usage\n./cmdarg.sh -n [name] -u [user id]"
   if [[ $# -lt 4 ]];then
     echo -e $usage
     exit 1
   fi
   
   #先保存参数到数组argv，再遍历数组argv提取参数
   for((i=0;i<=$#;i++))
   do
     argv[$i]=`eval echo '$'"$i"`
     echo "$i, ${argv[$i]}"
   done
   
   for((i=0;i<$#;i++))
   do
     case ${argv[$i]} in
       -s) let i+=1
           name=${argv[$i]};;
       -u) let i+=1
           user_id=${argv[$i]};;
     esac
   done
   
   echo "name is $name, user id is $user_id"
   
   
   [root@localhost debug]# ./cmdarg.sh -s tom -u 101
   0, ./cmdarg.sh
   1, -s
   2, tom
   3, -u
   4, 101
   name is tom, user id is 101

8. shell替换文件指定字符串为包含全局环境变量的字符串

   [root@localhost debug]# cat hello.sh 
   #!/bin/bash
   
   hello=1
   echo $hello
   
   [root@localhost debug]# export NAME=GrassInWind
   引用全局的环境变量需要使用'''包含在内部
   [root@localhost debug]# cat replace_with_env.sh 
   #!/bin/bash
   
   sed -i 's@hello=1@hello="hello from '''$NAME'''!"@g' hello.sh
   
   [root@localhost debug]# ./replace_with_env.sh 
   [root@localhost debug]# 
   [root@localhost debug]# cat hello.sh 
   #!/bin/bash
   
   hello="hello from GrassInWind!"
   echo $hello
   

9.  shell在指定字符串所在行下一行添加一行

   [root@localhost debug]# sed -i '/hello=/a\hi=1' hello.sh
   [root@localhost debug]# cat hello.sh 
   #!/bin/bash
   
   hello="hello from GrassInWind!"
   hi=1
   echo $hello
   

10. shell用指定字符串替换文件中包含指定字符串的整行内容

    [root@centos-docker root]# cat replaceIp.sh 
    #!/bin/bash
    
    file=test.txt
    ip="192.168.3.100"
    sed -i 's/"serviceIp".*/"serviceIp":"'''$ip'''",/g' $file
    
    [root@centos-docker root]# cat test.txt 
    {
        "test1":1,
        "test2":2,
        "serviceIp":"172.16.1.100",
        "test3":3
    }
    
    [root@centos-docker root]# ./replaceIp.sh 
    [root@centos-docker root]# cat test.txt 
    {
        "test1":1,
        "test2":2,
        "serviceIp":"192.168.3.100",
        "test3":3
    }
    

    通过sed命令可以替换文件内容，'s/"serviceIp".*/"serviceIp":"'''$ip'''",/g'表示将文件中满足"serviceIp"开头的任意内容替换为"serviceIp":"$ip"，$ip是期望替换的IP变量。

11. shell解压rpm包

    rpm2cpio test.rpm | cpio -idmv