如何使用uboot测试命令'or' -o选项

Question

从下面的输出来看，该命令似乎不适用于整数或 true 和 false 命令，那么 test -o（或）命令的预期用途是什么？

=> version
U-Boot 2017.01 (Apr 01 2021 - 00:00:00 +0000)
arm-poky-linux-gnueabi-gcc (GCC) 9.3.0
GNU ld (GNU Binutils) 2.34.0.20200220
=> if test 0 -o 0; then echo yeehaw; else echo yeenaw; fi
yeehaw
=> if test 1 -o 0; then echo yeehaw; else echo yeenaw; fi
yeehaw
=> if test 0 -o 1; then echo yeehaw; else echo yeenaw; fi
yeehaw
=> if test 0 -o 0; then echo yeehaw; else echo yeenaw; fi
yeehaw
=> if test 1 -o 1; then echo yeehaw; else echo yeenaw; fi
yeehaw
=> if test false -o false; then echo yeehaw; else echo yeenaw; fi
yeehaw
=> if test true -o false; then echo yeehaw; else echo yeenaw; fi
yeehaw
=> if test false -o true; then echo yeehaw; else echo yeenaw; fi
yeehaw
=> if test true -o true; then echo yeehaw; else echo yeenaw; fi
yeehaw

Answer 1

如果字符串为 non-empty，则认为该字符串为真，如果为空则为假：

$ if test ""; then echo true; else echo false; fi
false
$ if test "x"; then echo true; else echo false; fi
true

因此test "" -o x为真。您还可以在更复杂的比较之间使用 -o：

# Make sure 0 < $x < 10
if test "$x" -le 0 -o "$x" -ge 10; then echo "out of range"; fi

但是，POSIX 建议使用可移植的 shell 构造 || 而不是依赖旧运算符 test -o。

如何使用uboot测试命令'or' -o选项

How to use uboot test command 'or' -o option

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test-command