bash脚本编程，在while循环多个条件 [英] Bash scripting, multiple conditions in while loop

问题描述

我想while循环使用两个条件的bash工作，得到一个简单的，但是从各种论坛尝试许多不同的语法后，我不能停止抛出一个错误。以下是我有：

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 ]

我也尝试：

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

...以及其他几个构造。我想这个循环继续，而 $统计是＆GT; 300 或者 $统计= 0 。

推荐答案

正确的选项是（增加推荐的顺序排列）：

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. 引用在的参数扩展[...]] 和（（...））是可选的;如果变量没有设置， -gt 和 -eq 将假定值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.

使用 $ 在里面可选的（（...）），但使用它可以帮助避免无意识的错误。如果统计没有设置，那么（（统计＆GT; 300））将承担统计== 0 ，但（（$统计高于300））。将产生一个语法错误

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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