#!/bin/bash read -p "请输入一个数字: " num if ((num < 0)); then echo "输入的数字是负数" elif ((num == 0)); then echo "输入的数字是零" else echo "输入的数字是正数" fi 在上面的示例中,首先使用read命令获取用户输入的数字,然后使用if else语句判断数字的正负性,并输出相应的结果。 腾讯
9. if [grep foo myfile] 初学者会错误地认为,[是 if 语法的一部分,正如 C 语言中的 if ()。但是事实并非如此,if 后面跟着的是一个命令,[是一个命令,它是内置命令 test 的简写形式,只不过它要求最后一个参数必须是]。下面两种写法是一样的: # POSIX if [ false ]; then echo "HELP"; fi if tes...
if...else 是一种条件语句，可以根据给定的条件执行不同的操作。这个语句通常用于控制程序的流程。Provid...
$ type -t if keyword 上面例子中,bash是文件,if是关键词。 快捷键 Bash 提供很多快捷键,可以大大方便操作。下面是一些最常用的快捷键,完整的介绍参见《行操作》一章。 Ctrl + L:清除屏幕并将当前行移到页面顶部。 Ctrl + C:中止当前正在执行的命令。 Shift + PageUp:向上滚动。 Shift + PageDown:向下滚动。
if [[ $var != *sub_string* ]]; then printf '%s\n' "sub_string is not in var." fi # 也可以在数组中运行 if [[ ${arr[*]} == *sub_string* ]]; then printf '%s\n' "sub_string is in array." fi使用case语句:case "$var" in *sub_string*) # Do stuff ;; *sub_string2...
~/.nvm/nvm.sh. Restarting your terminal/opening a new tab/window, or running the source command will load the command and the new configuration. If the above didn't help, you might need to restart your terminal instance. Try opening a new tab/window in your terminal and retry....
if[[$foo=~$re]] 36. [ -n $foo ] or [ -z $foo ] 这个例子中,$foo 没有用引号引起来,当 $foo 包含空格或者 $foo 为空时都会出问题: $ foo="some word"&& [ -n$foo] &&echoyes -bash: [: some: binary operator expected $ foo=""&& [ -n$foo] &&echoyes ...
Simple commands, which are usually run by themselves or with parameters and variables. Pipes, which are used to link the output of one or more commands as input to other commands. Lists, which enable users to run multiple commands in sequence. ...
if [[ $1 =~ ^(#?([a-fA-F0-9]{6}|[a-fA-F0-9]{3}))$ ]]; then printf '%s\n' "${BASH_REMATCH[1]}" else printf '%s\n' "error: $1 is an invalid color." return 1 fi } read -r color is_hex_color "$color" || color="#FFFFFF"#Do stuff. ...
Comparison operators are used in bash to compare two strings to check if they are equal or not. Here, we will list some comparison operators including, string, and integer operators. Integer Operators Regular Expressions Regular expressions are shortened as ‘regexp' or ‘regex'. They are string...