Bash 脚本错误 [: !=: 预期的一元运算符
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Bash script error [: !=: unary operator expected
提问by user3380240
In my script I am trying to error check if the first and only argument is equal to -v but it is an optional argument. I use an if statement but I keep getting the unary operator expected error.
在我的脚本中，我试图错误检查第一个也是唯一的参数是否等于 -v 但它是一个可选参数。我使用 if 语句，但我不断收到一元运算符预期的错误。
this is the code:
这是代码：
if [ != -v ]; then
echo "usage: #!/bin/bash
if [ "$#" -gt "1" ]; then
echo "usage: if [ "" != -v ]; then
[-v]"
exit
fi
if [ "" != -v ]; then
echo "usage: [ != -v ]
[-v]"
exit
fi
if [ "" = -v ]; then
echo "`ps -ef | grep -v '\['`"
else
echo "`ps -ef | grep '\[' | grep root`"
fi
[-v]"
exit
fi
Edit:
编辑：
I should be more specific: This part of the script above is checking an optional argument and then after, if the argument is not entered, it should run the rest of the program.
我应该更具体：上面脚本的这一部分正在检查一个可选参数，然后，如果没有输入该参数，它应该运行程序的其余部分。
[ "" != -v ]
回答by Charles Duffy
Quotes!
引号！
#!/bin/sh
case in
'-v') if [ "" = -v ]; then
echo "`ps -ef | grep -v '\['`"
else
echo "`ps -ef | grep '\[' | grep root`"
fi;;
*) echo "usage: #!/bin/sh
usage ()
{
echo "usage: $ adduser -u:sam -s -f -u:bob -trace -verbose
[-v]"
exit 1
}
unset arg_match
for arg in $*
do
case $arg in
'-v') if [ "$arg" = -v ]; then
echo "`ps -ef | grep -v '\['`"
else
echo "`ps -ef | grep '\[' | grep root`"
fi
arg_match=1;; # this is set, but could increment.
*) ;;
esac
done
if [ ! $arg_match ]
then
usage
fi
[-v]"
exit 1;; #It is good practice to throw a code, hence allowing $? check
esac
Otherwise, when $1is completely empty, your test becomes:
否则，当$1完全为空时，您的测试将变为：
$ adduser -u sam -s -f -u bob -trace -verbose
instead of
代替
##代码##...and !=is not a unary operator (that is, one capable of taking only a single argument).
...并且!=不是一元运算符（即只能接受一个参数的运算符）。
回答by SMullaney
Or for what seems like rampant overkill, but is actually simplistic ... Pretty much covers all of your cases, and no empty string or unary concerns.
或者对于看似猖獗的矫枉过正，但实际上很简单......几乎涵盖了您的所有案例，没有空字符串或一元问题。
In the case the first arg is '-v', then do your conditional ps -ef, else in all other cases throw the usage.
在第一个参数是'-v'的情况下，然后做你的条件ps -ef，否则在所有其他情况下抛出用法。
If one cares not where the '-v' arg is, then simply drop the case inside a loop. The would allow walking all the args and finding '-v' anywhere (provided it exists). This means command line argument order is not important. Be forewarned, as presented, the variable arg_match is set, thus it is merely a flag. It allows for multiple occurrences of the '-v' arg. One could ignore all other occurrences of '-v' easy enough.
如果人们不关心 '-v' arg 在哪里，那么只需将案例放入循环中即可。这将允许遍历所有参数并在任何地方找到“-v”（如果它存在）。这意味着命令行参数顺序并不重要。预先警告，如上所述，变量 arg_match 已设置，因此它只是一个标志。它允许多次出现“-v”参数。人们可以很容易地忽略所有其他出现的“-v”。
##代码##But, allow multiple occurrences of an argument is convenient to use in situations such as:
但是，允许参数多次出现在以下情况下使用起来很方便：
##代码##We care not about the order of the arguments, and even allow multiple -u arguments. Yes, it is a simple matter to also allow:
我们不关心参数的顺序，甚至允许多个 -u 参数。是的，还允许：
##代码##