检查shell脚本中的字符串是否既不为空也不为空 [英] Check if string is neither empty nor space in shell script

问题描述

我正在尝试运行以下shell脚本，该脚本应检查字符串是否既不是空格也不为空.但是，对于所有上述3个字符串，我都得到相同的输出.我也尝试过使用[[]语法，但无济于事.

I am trying to run the following shell script which is supposed to check if a string is neither space nor empty. However, I am getting the same output for all the 3 mentioned strings. I have tried using the "[[" syntax as well but to no avail.

这是我的代码:

str="Hello World"
str2=" "
str3=""

if [ ! -z "$str" -a "$str"!=" " ]; then
        echo "Str is not null or space"
fi

if [ ! -z "$str2" -a "$str2"!=" " ]; then
        echo "Str2 is not null or space"
fi

if [ ! -z "$str3" -a "$str3"!=" " ]; then
        echo "Str3 is not null or space"
fi

我得到以下输出:

# ./checkCond.sh 
Str is not null or space
Str2 is not null or space

推荐答案

您需要在!=的两边都留一个空格.将您的代码更改为:

You need a space on either side of the !=. Change your code to:

str="Hello World"
str2=" "
str3=""

if [ ! -z "$str" -a "$str" != " " ]; then
        echo "Str is not null or space"
fi

if [ ! -z "$str2" -a "$str2" != " " ]; then
        echo "Str2 is not null or space"
fi

if [ ! -z "$str3" -a "$str3" != " " ]; then
        echo "Str3 is not null or space"
fi

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