When you execute a command or run a script, you receive anexit code. An exit code is a system response that reports success, an error, or another condition that provides a clue about what caused an unexpected result from your command or script. Yet, you might never know about the code,...
(If n is omitted, the exit status is that of the last command executed. ) 格式:$? 上一个命令的退出码。 格式:trap "commands" EXIT 退出时执行commands指定的命令。( A trap on EXIT is executed before the shell terminates.) 退出码(exit status,或exit code)的约定: 0表示成功(Zero - Success...
When you execute a command or run a script, you receive anexit code. An exit code is a system response that reports success, an error, or another condition that provides a clue about what caused an unexpected result from your command or script. Yet, you might never know about the code,...
last | cut -d ' ' -f 1 | sort | uniq#这个命令所实现的就是将last输出的每行数据使用空格切割并取出第一个片段输出,然后排序再取出不重复的数据 last | cut -d ' ' -f 1 | sort -u#这行命令实现的操作与上一行命令一致,但sort没有计数功能,如果要使用计数功能还是需要使用uniq命令 last | cut ...
$!" # 返回最近一个后台命令的进程 ID sleep 1 echo "the last parameter of the previous command: \$_ $_" # 上一个命令的最后一个参数, 比如这里是1 选项参数传递 getopts 是一个用于解析命令行选项和参数的内置命令, 语法为 getopts optstring name optstring 是一个字符串, 定义脚本可以接收的选项, ...
Code: #!/bin/bashecho"Hello, world!" Copy Output: ad@DESKTOP-3KE0KU4:~$ ./test1.sh Hello, world! Explanation: In the exercise above, echo "Hello, world!": This command prints the string "Hello, world!" to the standard output. The "echo" command is used to output text to the ...
$? # Exit status of last task $! # PID of last background task $$ # PID of shell $0 # Filename of the shell script $_ # Last argument of the previous command 检查命令返回值 if ping -c 1 google.com; then echo "It appears you have a working internet connection" fi 检查grep 的...
The $_ variable stores the last argument of the last command. : always succeeds so it can be used to store the variable value.# Modified snippet from Neofetch. case "$OSTYPE" in "darwin"*) : "MacOS" ;; "linux"*) : "Linux" ;; *"bsd"* | "dragonfly" | "bitrig") : "BSD" ...
seq Displays an incremental sequence of numbers from first to last. service This command is used to manage system services. set Used to manipulate shell variables and functions. setfdprm Sets floppy disk parameters as provided by the user. setkeycodes Load kernel scancode-to-keycode mapping table...
The exit status of the wait command is printed. $? is an internal Bash variable that holds the exit status of the last command executed. If you run the script, it will print something like this: PID:36353Exit status:0 Here’s an example using the -n option: ...