一元运算符预期 [英] unary operator expected
问题描述
我一直试图弄清楚什么是错与此,但就是无法弄清楚..
这是部分似乎得到一个错误。
的elif [$操作=人];然后
如果[$ AUG1 =添加];然后#< - 75号线
回声手册页:加上
回声
回声语法:加[数字1] [2号]
回声
回声简介:
回声添加两个不同的数字加在一起。
回声
回声信息:
回声中新增V1.0
回声
ELIF [-z $ AUG1]。然后
回声请指定一个命令来阅读man page。
其他
回声有该命令没有手册页。
科幻
我得到这个错误:
calc_1.2:75行:[:=:一元运算符预期
如果你知道你总是要使用bash,它更容易为始终使用双支架有条件的复合命令 [。 ..]
,而不是符合POSIX标准的单支架版本 [...]
。在 [...]
复合,字的拆分和路径扩展不会应用到的话,那么你可以依靠
如果[[$ AUG1 ==和]];
到 $ AUG1
的值与字符串比较和
。
如果您使用 [...]
,你总是需要记住翻一番这样的引用变量:
如果[$ AUG1=和];
如果你不引用变量扩展和变量未定义或空的,它从犯罪现场消失了,只留下
如果[=和];
这不是有效的语法。 (这也将失败,不同的错误消息,如果 $ AUG1
包含空格或shell转义字符。)
现代 [
经营者有很多其他不错的功能,包括常规的前pression匹配。
I've been trying to figure out whats wrong with this but just can't figure it out..
This is the part seems to be getting an error..
elif [ $operation = "man" ]; then
if [ $aug1 = "add" ]; then # <- Line 75
echo "Man Page for: add"
echo ""
echo "Syntax: add [number 1] [number 2]"
echo ""
echo "Description:"
echo "Add two different numbers together."
echo ""
echo "Info:"
echo "Added in v1.0"
echo ""
elif [ -z $aug1 ]; then
echo "Please specify a command to read the man page."
else
echo "There is no manual page for that command."
fi
I get this error:
calc_1.2: line 75: [: =: unary operator expected
If you know you're always going to use bash, it's much easier to always use the double bracket conditional compound command [[ ... ]]
, instead of the Posix-compatible single bracket version [ ... ]
. Inside a [[ ... ]]
compound, word-splitting and pathname expansion are not applied to words, so you can rely on
if [[ $aug1 == "and" ]];
to compare the value of $aug1
with the string and
.
If you use [ ... ]
, you always need to remember to double quote variables like this:
if [ "$aug1" = "and" ];
If you don't quote the variable expansion and the variable is undefined or empty, it vanishes from the scene of the crime, leaving only
if [ = "and" ];
which is not a valid syntax. (It would also fail with a different error message if $aug1
included white space or shell metacharacters.)
The modern [[
operator has lots of other nice features, including regular expression matching.
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