bash 使用 grep 比较两个字符串
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/22631415/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
compare two strings using grep
提问by Asish Pati
echo "abc-vcu def" | grep -w "abc.vcu"
echo $?
The output of the above line is 0. But abc-vcu!= abc.vcuand def!= abc.vcu. So it should return 1.
上面一行的输出是0. 但是abc-vcu!=abc.vcu和def!= abc.vcu。所以它应该返回1。
Command is returning true because it is assuming .and -are same. How to do exact comparing?
命令返回 true 因为它假设.并且-是相同的。如何进行精确比较？
回答by Gennadiy Litvinyuk
In grep .means any character(regular expression syntax)
在 grep 中.表示任何字符（正则表达式语法）
If you need to match .try \.
如果你需要匹配.试试\.
echo "abc-vcu def" | grep -w "abc\.vcu"
echo $?
回答by Adaephon
Instead of using grepyou could let bashdo the work, especially if you intend to use variables anyway:
grep您可以让我们bash完成工作，而不是使用，特别是如果您打算使用变量：
string1='abc-vcu def'
string2='abc.vcu'
[[ ! ${string1/*${string2}*/} ]]
echo $?
[[ expression ]]returns 0or 1depending on the evaluation of expression.
[[ expression ]]返回0或1取决于 的评估expression。
!is a logical not.
!是合乎逻辑的不。
${parameter/pattern/string}replaces the first occurence of patternin parameterby string, where patternis expanded just as in pathname expansions. For the above case that means that if $string2appears anywhere in $string1, $string1is completely replaced by ''(an empty string), which is a logical false.
${parameter/pattern/string}替换第一次出现pattern在parameter由string其中pattern的，就像路径扩展扩展。对于上述情况，这意味着 if$string2出现在 中的任何地方$string1，$string1完全被''（空字符串）替换，这是一个逻辑假。
回答by tripleee
What you are attempting is better achieved with a simple string comparison.
通过简单的字符串比较可以更好地实现您的尝试。
if [[ "abc-vcu def" == *"abc.vcu"* ]]; then
echo "String B contained in String A"
else
echo "No containment"
fi
Notice also how this avoids the antipattern of examining $?. Just to elaborate, anything that looks like
还要注意这如何避免检查的反模式$?。只是详细说明，任何看起来像
command
if [ $? == 0 ]; then ...
is better written as
最好写成
if command; then ...
Tangentially, if you really do want or have to use grep, there are some options you need to understand. grepmatches regular expressions, not just strings. There is a separate option to change the search expression into a string, namely -F(traditionally available as a separate command fgrep):
切线地讲，如果您确实想要或必须使用grep，则需要了解一些选项。 grep匹配正则表达式，而不仅仅是字符串。有一个单独的选项可以将搜索表达式更改为字符串，即-F（传统上作为单独的命令可用fgrep）：
echo moo | grep m.o # true
echo moo | grep -F m.o # false
Just for completeness, note also that greplooks for a match anywhere in the input. So echo moo | grep ois true. If you really want to look for an exact match, you need the -xoption (or change the expression you are grepping for):
只是为了完整性，还要注意grep在输入中的任何地方寻找匹配。所以，echo moo | grep o是真实的。如果您真的想查找完全匹配，则需要该-x选项（或更改您要查找的表达式）：
echo moo | grep -x moo
echo moo | grep '^moo$'
Like @Kent remarks, grepwill print any matching lines by default, which you probably don't want here -- you are only running grepto see if there is a match. So you need the -qflag as well. To summarize,
就像@Kent 的评论一样，grep默认情况下会打印任何匹配的行，您可能不希望在此处打印 - 您只是在运行grep以查看是否存在匹配项。所以你也需要-q旗帜。总结一下，
echo "abc-vcu def" | grep -Fxwq "abc.vcu"
Finally, you should probably also be aware of case:
最后，您可能还应该知道case：
case "abc-vcu def" in *"abc.vcu"*) echo true;; *) echo false;; esac
Unlike the [[Bash-only test, caseis portable all the way back to the original Bourne shell.
与[[Bash-only 测试不同，它case可以一直移植到原始的 Bourne shell。
回答by Sergey Fedorov
If you do want to use grepin this case, use it as follows:
如果您确实想grep在这种情况下使用，请按如下方式使用它：
echo "abc-vcu def" | grep -F -w "abc.vcu"
man grepsays that with -Fgrep must
man grep说-Fgrep 必须
Interpret PATTERN as a list of fixed strings
将 PATTERN 解释为固定字符串列表
This fixes the problem that .is recognized as 'any symbol' pattern.
这解决了.被识别为“任何符号”模式的问题。
