bash的工作特性之命令執行狀態返回值和命令行展開所涉及的內容

bash的工作特性之命令執行狀態返回值和命令行展開所涉及的內容

bash的基礎特性：命令的執行狀態結果

bash通過狀態返回值來輸出此結果：

    成功：0
    失?。?-255

命令執行完成之后，其狀態返回值保存于bash的特殊變量$?中。

    [root@localhost ~]# ls
    anaconda-ks.cfg
    [root@localhost ~]# echo $?
    0
    [root@localhost ~]# asd
    -bash: asd: command not found
    [root@localhost ~]# echo $?
    127
    [root@localhost ~]# 

bash的基礎特性：命令行展開

{}：可承載一個以逗號分隔的路徑列表，并能夠將其展開為多個路徑；

        例如：/tmp/{a,b} 相當于 /tmp/a /tmp/b

實例

• 創建/tmp目錄下的：ac, ad, bc, bd

  [root@localhost ~]# mkdir -pv /tmp/{a_c,a_d,b_c,b_d}
  mkdir: created directory ‘/tmp/a_c’
  mkdir: created directory ‘/tmp/a_d’
  mkdir: created directory ‘/tmp/b_c’
  mkdir: created directory ‘/tmp/b_d’
  [root@localhost ~]# ll /tmp
  total 8
  drwxr-xr-x. 2 root root   6 Mar 11 22:46 a_c
  drwxr-xr-x. 2 root root   6 Mar 11 22:46 a_d
  drwxr-xr-x. 2 root root   6 Mar 11 22:46 b_c
  drwxr-xr-x. 2 root root   6 Mar 11 22:46 b_d
  

• 創建目錄結構

  [root@localhost ~]# mkdir -pv /tmp/mylinux/{bin,boot/grub,dev,etc/{rc.d/init.d,sysconfig/network-scripts},lib/modules,lib64,proc,sbin,sys,tmp,usr/local/{bin,sbin},var/{lock,log,run}}
  mkdir: created directory ‘/tmp/mylinux’
  mkdir: created directory ‘/tmp/mylinux/bin’
  mkdir: created directory ‘/tmp/mylinux/boot’
  mkdir: created directory ‘/tmp/mylinux/boot/grub’
  mkdir: created directory ‘/tmp/mylinux/dev’
  mkdir: created directory ‘/tmp/mylinux/etc’
  mkdir: created directory ‘/tmp/mylinux/etc/rc.d’
  mkdir: created directory ‘/tmp/mylinux/etc/rc.d/init.d’
  mkdir: created directory ‘/tmp/mylinux/etc/sysconfig’
  mkdir: created directory ‘/tmp/mylinux/etc/sysconfig/network-scripts’
  mkdir: created directory ‘/tmp/mylinux/lib’
  mkdir: created directory ‘/tmp/mylinux/lib/modules’
  mkdir: created directory ‘/tmp/mylinux/lib64’
  mkdir: created directory ‘/tmp/mylinux/proc’
  mkdir: created directory ‘/tmp/mylinux/sbin’
  mkdir: created directory ‘/tmp/mylinux/sys’
  mkdir: created directory ‘/tmp/mylinux/tmp’
  mkdir: created directory ‘/tmp/mylinux/usr’
  mkdir: created directory ‘/tmp/mylinux/usr/local’
  mkdir: created directory ‘/tmp/mylinux/usr/local/bin’
  mkdir: created directory ‘/tmp/mylinux/usr/local/sbin’
  mkdir: created directory ‘/tmp/mylinux/var’
  mkdir: created directory ‘/tmp/mylinux/var/lock’
  mkdir: created directory ‘/tmp/mylinux/var/log’
  mkdir: created directory ‘/tmp/mylinux/var/run’
  [root@localhost ~]# tree /tmp/mylinux
  /tmp/mylinux
  ├── bin
  ├── boot
  │?? └── grub
  ├── dev
  ├── etc
  │?? ├── rc.d
  │?? │?? └── init.d
  │?? └── sysconfig
  │??     └── network-scripts
  ├── lib
  │?? └── modules
  ├── lib64
  ├── proc
  ├── sbin
  ├── sys
  ├── tmp
  ├── usr
  │?? └── local
  │??     ├── bin
  │??     └── sbin
  └── var
      ├── lock
      ├── log
      └── run
  
  24 directories, 0 files