shell脚本中$#、$*、$@、$?、$0等含义一文搞懂

旧城等待， 2023-10-08 16:03 9阅读 0赞

## 一、Shell脚本变量的含义 ##

1、$\#：表示执行脚本传入参数的个数

2、$\*：表示执行脚本传入参数的列表（不包括$0）

3、$$：表示进程的id；Shell本身的PID（ProcessID，即脚本运行的当前 进程ID号）

4、$!：Shell最后运行的后台Process的PID(后台运行的最后一个进程的 进程ID号)

5、$@：表示执行脚本传入参数的所有个数（不包括$0）

6、$0：表示执行的脚本名称

7、$1：表示第一个参数

8、$2：表示第二个参数

9、$?：表示脚本执行的状态，0表示正常，其他表示错误

## 二 $ ∗ 和 \*和 ∗和 $@的差异 ##

在shell中，KaTeX parse error: Can't use function '$' in math mode at position 3: @和$̲ $\*都表示命令行所有的参数（…@则区分各个参数  
Demo 脚本示例：

cat ./tmp/shll_test/test.sh
    #!/bin/sh
     
    MY_SHELL_PATH=`dirname $0`
     
    echo "print shell script location:"
    echo ${
        MY_SHELL_PATH}
    echo "===================================="
     
    echo "enter shell script location:${MY_SHELL_PATH}"
    cd `dirname $0`
    echo "list current directory content:"
    ls -lh
    echo "===================================="
     
    echo "shell script name=${0}"
    echo "===================================="
     
    echo "first args=${1}"
    echo "===================================="
     
    echo "second args=${2}"
    echo "===================================="
     
    echo "arguments number=$#"
    echo "===================================="
     
    echo "arguments list content=$@"
    echo "===================================="
     
    echo "arguments list content=$*"
    echo "===================================="
     
    echo "the process id is " "$$"
    echo "===================================="
     
    echo "the shell execute return value is " "$?"
    echo "===================================="
     
    echo "the all paramters:"
    for i in "$@"
      do
        echo $i  #循环$#次
      done
    echo "===================================="
     
     
     
    echo "the all paramters:"
    for i in "$*"
      do
        echo $i
      done
    echo "===================================="

结果：

[root@t4-algo-7 /]# pwd
    /
    [root@t4-algo-7 /]# ll
    total 76
    lrwxrwxrwx.   1 root root     7 Nov 29  2018 bin -> usr/bin
    dr-xr-xr-x.   5 root root  4096 Nov 29  2018 boot
    drwxr-xr-x   19 root root  3120 Dec 29 10:05 dev
    drwxr-xr-x.  84 root root  4096 Jan 12 15:29 etc
    drwxr-xr-x.   7 root root  4096 Dec 31 12:00 home
    lrwxrwxrwx.   1 root root     7 Nov 29  2018 lib -> usr/lib
    lrwxrwxrwx.   1 root root     9 Nov 29  2018 lib64 -> usr/lib64
    drwx------.   2 root root 16384 Nov 29  2018 lost+found
    drwxr-xr-x.   2 root root  4096 Apr 11  2018 media
    drwxr-xr-x.   4 root root  4096 Dec 31 11:02 mnt
    drwxr-xr-x.   6 root root  4096 Jan 12 11:53 opt
    dr-xr-xr-x  400 root root     0 Jan  7  2020 proc
    dr-xr-x---.  22 root root  4096 Jan 12 18:27 root
    drwxr-xr-x   27 root root   840 Jan 12 12:01 run
    lrwxrwxrwx.   1 root root     8 Nov 29  2018 sbin -> usr/sbin
    drwxr-xr-x.   2 root root  4096 Apr 11  2018 srv
    dr-xr-xr-x   13 root root     0 Mar 23  2020 sys
    drwxrwxrwt.  12 root root 20480 Jan 12 18:34 tmp
    drwxr-xr-x.  13 root root  4096 Nov 29  2018 usr
    drwxr-xr-x.  19 root root  4096 Nov 29  2018 var
     
    [root@t4-algo-7 shll_test]# pwd
    /tmp/shll_test
    [root@t4-algo-7 shll_test]# yum install -y tree
    [root@t4-algo-7 shll_test]# tree 
    .
    ├── dir1
    │   └── dir2
    ├── file.txt
    └── test.sh
     
    2 directories, 2 files
    [root@t4-algo-7 shll_test]#
    [root@t4-algo-7 /]# ./tmp/shll_test/test.sh 1 2 3,4
    print shell script location:
    ./tmp/shll_test
    ====================================
    enter shell script location:./tmp/shll_test
    list current directory content:
    total 8.0K
    drwxr-xr-x 3 root root 4.0K Jan 12 18:22 dir1
    -rw-r--r-- 1 root root    0 Jan 12 18:22 file.txt
    -rwxr-xr-x 1 root root 1.2K Jan 12 18:50 test.sh
    ====================================
    shell script name=./tmp/shll_test/test.sh
    ====================================
    first args=1
    ====================================
    second args=2
    ====================================
    arguments number=3
    ====================================
    arguments list content=1 2 3,4
    ====================================
    arguments list content=1 2 3,4
    ====================================
    the process id is  6152
    ====================================
    the shell execute return value is  0
    ====================================
    the all paramters:
    1
    2
    3,4
    ====================================
    the all paramters:
    1 2 3,4
    ====================================
    [root@t4-algo-7 /]#