./empty_string.sh: line 5: test: go: binary operator expected ./empty_string.sh: line 9: [: go: binary operator expected (3) -n "$1": Quote : not empty. $ ./empty_string.sh (1) -n $1 : No quote: not empty. (2) -z $1 : No quote: empty. (4) -z "$1": Quote ...
用户可以对自己的运行环境进行定制，其方法就是修改相应的系统环境变量。 常见的环境变量： PATH： ...
$ ./checkarg'''./checkarg: line5:1: A non-empty argument is required $ ./checkarg x''./checkarg: line5:2: Two non-empty arguments are required $ ./checkarg x x Thank you. (5) ${#var}: 变量内容的长度 readpasswdif[ ${#passwd} -lt8]thenprintf"Password is too short: %d c...
echo "The first or second number is empty." else #Calculate the sum sum=$(($n1+$n2)) #Print the summation value echo "The sum of $n1 and $n2 is $sum." fi Output: The following output appears if the script is executed without any argument: The following output appears if the scri...
1) if ... else 语句 2) if ... else ... fi 语句 23.2 输入重定向 23.3 重定向深入讲解 Here Document /dev/null 文件 1. Shell简介 Shell本身是一个用C语言编写的程序,它是用户使用Unix/Linux的桥梁,用户的大部分工作都是通过Shell完成的。Shell既是一种命令语言,又是一种程序设计语言。作为命令语言...
How to do string comparison and check if a string equals to a value? How to check if a string is in an array? How to use the Bash ternary operator? How to negate an if condition in a Bash if statement? (if not command or if not equal) How to use the BASH_REMATCH variable with...
whiletrue;docase"$1"in-a|--a-long)echo"Option a";shift;;-b|--b-long)echo"Option b, argument \`$2'";shift2;;-c|--c-long)# c has an optional argument.As we areinquoted mode,# an empty parameter will be generatedifits optional...
-b|--b-long) echo "Option b, argument \`$2'" ; shift 2 ;; -c|--c-long) # c has an optional argument. As we are in quoted mode, # an empty parameter will be generated if its optional # argument is not found. case "$2" in ...
# 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 的返回值 if grep -q 'foo' ~/.bash_...
echo"Input argument exists." Here the “-z” option is used with the “test” command to check if the input argument is an empty string or not. The script will output an error message and exit with a status code of 1 if the input argument is an empty string. Otherwise, the script ...