Bash 脚本，while 循环中的多个条件
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Bash scripting, multiple conditions in while loop
提问by jake9115
I'm trying to get a simple while loop working in bash that uses two conditions, but after trying many different syntax from various forums, I can't stop throwing an error. Here is what I have:
我试图在使用两个条件的 bash 中获得一个简单的 while 循环，但是在尝试了来自各种论坛的许多不同语法之后，我无法停止抛出错误。这是我所拥有的：
while [ $stats -gt 300 ] -o [ $stats -eq 0 ]
I have also tried:
我也试过：
while [[ $stats -gt 300 ] || [ $stats -eq 0 ]]
... as well as several others constructs. I want this loop to continue while $stats is > 300or if $stats = 0.
...以及其他几个结构。我希望这个循环继续 while$stats is > 300或 if $stats = 0。
回答by chepner
The correct options are (in increasing order of recommendation):
正确的选项是（按推荐的递增顺序）：
# Single POSIX test command with -o operator (not recommended anymore).
# Quotes strongly recommended to guard against empty or undefined variables.
while [ "$stats" -gt 300 -o "$stats" -eq 0 ]
# Two POSIX test commands joined in a list with ||.
# Quotes strongly recommended to guard against empty or undefined variables.
while [ "$stats" -gt 300 ] || [ "$stats" -eq 0 ]
# Two bash conditional expressions joined in a list with ||.
while [[ $stats -gt 300 ]] || [[ $stats -eq 0 ]]
# A single bash conditional expression with the || operator.
while [[ $stats -gt 300 || $stats -eq 0 ]]
# Two bash arithmetic expressions joined in a list with ||.
# $ optional, as a string can only be interpreted as a variable
while (( stats > 300 )) || (( stats == 0 ))
# And finally, a single bash arithmetic expression with the || operator.
# $ optional, as a string can only be interpreted as a variable
while (( stats > 300 || stats == 0 ))
Some notes:
一些注意事项：
Quoting the parameter expansions inside
[[ ... ]]and((...))is optional; if the variable is not set,-gtand-eqwill assume a value of 0.Using
$is optional inside(( ... )), but using it can help avoid unintentional errors. Ifstatsisn't set, then(( stats > 300 ))will assumestats == 0, but(( $stats > 300 ))will produce a syntax error.
引用里面的参数扩展
[[ ... ]]并且((...))是可选的；如果变量没有被设置，-gt并且-eq将假设值0。$在 内部使用是可选的(( ... ))，但使用它可以帮助避免意外错误。如果stats未设置，则(( stats > 300 ))假定为stats == 0，但(( $stats > 300 ))会产生语法错误。
回答by drewmm
Try:
尝试：
while [ $stats -gt 300 -o $stats -eq 0 ]
[is a call to test. It is not just for grouping, like parentheses in other languages. Check man [or man testfor more information.
[是对 的调用test。它不仅仅是用于分组，就像其他语言中的括号一样。检查man [或man test了解更多信息。
回答by Lighthart
The extra [ ] on the outside of your second syntax are unnecessary, and possibly confusing. You may use them, but if you must you need to have whitespace between them.
第二种语法外部的额外 [ ] 是不必要的，并且可能会造成混淆。您可以使用它们，但如果必须，您需要在它们之间留有空格。
Alternatively:
或者：
while [ $stats -gt 300 ] || [ $stats -eq 0 ]
