Bash 脚本，while 循环中的多个条件 [英] Bash scripting, multiple conditions in while loop

问题描述

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:

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:

while [ $stats -gt 300 ] -o [ $stats -eq 0 ]

我也试过:

while [[ $stats -gt 300 ] || [ $stats -eq 0 ]]

... 以及其他几个结构.我希望这个循环继续，而 $stats 是 >300 或者如果 $stats = 0.

... as well as several others constructs. I want this loop to continue while $stats is > 300 or if $stats = 0.

推荐答案

正确的选项是(按推荐的升序):

The correct options are (in increasing order of recommendation):

# 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 ))

一些注意事项:

1. 引用[[ ... ]] 和((...)) 中的参数扩展是可选的；如果未设置变量，-gt 和 -eq 将假定值为 0.

1. Quoting the parameter expansions inside [[ ... ]] and ((...)) is optional; if the variable is not set, -gt and -eq will assume a value of 0.

在 (( ... )) 中使用 $ 是可选的，但使用它有助于避免意外错误.如果 stats 未设置，则 (( stats > 300 )) 将假定 stats == 0，但 (($stats > 300 )) 会产生语法错误.

Using $ is optional inside (( ... )), but using it can help avoid unintentional errors. If stats isn't set, then (( stats > 300 )) will assume stats == 0, but (( $stats > 300 )) will produce a syntax error.

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