I am stuck with matching scientific notation of floating point numbers with grep using the regular expression. My problem is as follows:
我坚持使用正则表达式将浮点数的科学符号与grep匹配。我的问题是:
I want to get all the floating point numbers (expressed in scientific notation) in a file, but there are other strings in this file as well. The file content likes like this:
我想在一个文件中获得所有浮点数(用科学符号表示)，但是这个文件中还有其他字符串。文件内容如下:
This product is subject to U.S. laws governing export and re-export.
Case run remote-shell.
33080 2.7122e-03 3.7837e-05 4.3489e-05 1.3267e-04 2.7229e-05 4.1196e-05 3.0528e-04 4.7660e-04 5.9506e-06 8.1338e-04 6.6428e-04 1.0230e-04 6.1385e-04 5.3061e-05 4.8918e-04 8.1832e-05 7.5350e-04 6.8355e-04 3.5495e-04 4.3668e-04 1.0076e-04 1.4759e-05 3.3033e-05 3.7662e-05 4.2165e-04 5.1842e-05 3.2158e-04 1.5356e-03 4.2839e-05 2.9283e-04 1.6930e-05 4.9191e-05 3.2135e-05 1.8665e-04 1.6677e-05 3.2952e-04 4.4912e-05 5.6932e-05 1.1145e-03 5.7499e-04 2.1972e-04 3.6925e-05 1.1579e-03 3.9610e-04 3.6176e-04 1.4320e-04 5.9517e-04 2.4946e-04 9.8161e-06 5.3642e-04 5.0760e-03 4.1630e-05 9.5973e-05 5.7817e-05 3.1283e-04 4.4210e-04 9.7502e-06 1.8566e+03 3.0613e-01 0:37:35 1922
33040 3.7547e-03 2.5260e-05 3.0029e-05 9.4277e-05 2.0479e-05 2.4130e-05 1.9597e-04 8.9547e-04 4.2917e-06 5.7030e-04 3.9776e-04 5.8403e-05 3.9431e-04 4.6212e-05 3.2378e-04 4.0916e-05 2.9765e-04 2.7011e-04 2.1954e-04 2.3628e-04 9.6072e-05 1.1480e-05 2.3660e-05 2.4469e-05 2.9498e-04 2.8080e-05 1.9791e-04 1.4410e-03 2.8925e-05 1.8617e-04 1.4366e-05 3.5216e-05 2.9843e-05 1.7923e-04 1.2372e-05 2.0673e-04 3.1176e-05 5.0167e-05 7.0653e-04 3.6454e-04 1.9928e-04 2.2903e-05 8.3425e-04 2.1208e-04 1.7543e-04 9.5440e-05 3.4135e-04 1.7607e-04 7.2080e-06 5.5701e-04 2.9932e-03 3.6117e-05 8.8722e-05 5.1176e-05 2.3192e-04 1.2000e-03 5.9996e-06 1.8570e+03 3.0613e-01 0:38:28 1962
I tried:
我试着:
grep "[0-9]*\.\?[0-9]*[eE][+-][0-9]*" filename
It can indeed filter out all the numbers in scientific notation. But words like re-export and remote-shell are also filtered out. Which is weird to me. Then I removed the \? qualifier:
它确实可以过滤掉科学符号中的所有数字。但是像再出口和远程shell这样的词也被过滤掉了。这对我来说很奇怪。然后我去掉了\?限定符:
grep "[0-9]*\.[0-9]*[eE][+-][0-9]*" filename
This time the words like re-export and remote-shell are not included. But I am really confused as the \? qualifier just represents the preceding item . (dot) is optional, why it makes all everything before it optional? Can anybody explain why this happens and provide a solution to just make the single item before the \? qualifier as optional as later on I also need to filter out numbers like this 2e-3
这一次不包括诸如再出口和远程shell等词。但是我真的很困惑?限定符只表示前面的项。(点)是可选的，为什么所有的东西都是可选的?谁能解释一下为什么会发生这种情况，并提供一种解决方案，使单个项目先于\?和后面的可选限定符一样，我还需要过滤像这个2 -3这样的数字
.
。
1 个解决方案
#1
2
The answer as to why it happens is easy: the only obligatory subpatterns in your regex are [eE][+-], so it will match any of e-, e+, E-, E+.
关于发生这种情况的原因，答案很简单:regex中惟一必需的子模式是[eE][+-]，因此它将匹配任何e-、e+、e-、e+。
You need to make the number part compulsory. It depends on what kind of number format you need to support, but in most cases you may use + quantifier to match 1 or more occurrences:
你需要使数字部分成为强制性的。这取决于您需要支持哪种数字格式，但是在大多数情况下，您可以使用+量词来匹配1个或多个事件:
"[0-9]*\.\?[0-9]\+[eE][+-][0-9]*"
^^
#1
2
The answer as to why it happens is easy: the only obligatory subpatterns in your regex are [eE][+-], so it will match any of e-, e+, E-, E+.
关于发生这种情况的原因，答案很简单:regex中惟一必需的子模式是[eE][+-]，因此它将匹配任何e-、e+、e-、e+。
You need to make the number part compulsory. It depends on what kind of number format you need to support, but in most cases you may use + quantifier to match 1 or more occurrences:
你需要使数字部分成为强制性的。这取决于您需要支持哪种数字格式，但是在大多数情况下，您可以使用+量词来匹配1个或多个事件:
"[0-9]*\.\?[0-9]\+[eE][+-][0-9]*"
^^