如何在模式后搜索内容? [英] How to grep for contents after pattern?

问题描述

给定一个文件，例如:

potato: 1234
apple: 5678
potato: 5432
grape: 4567
banana: 5432
sushi: 56789

我想对所有以 potato: 开头的行进行 grep，但只传递 potato: 后面的数字.所以在上面的例子中，输出将是:

I'd like to grep for all lines that start with potato: but only pipe the numbers that follow potato:. So in the above example, the output would be:

1234
5432

我该怎么做?

推荐答案

grep 'potato:' file.txt | sed 's/^.*: //'

grep 查找任何行包含字符串 potato:，然后，对于每一行，sed 从行的开头替换(s/// - 替换)任何字符 (.*)(^) 直到最后一次出现序列 :(冒号后跟空格)和空字符串 (s/...//- 将第一部分替换为空的第二部分).

grep looks for any line that contains the string potato:, then, for each of these lines, sed replaces (s/// - substitute) any character (.*) from the beginning of the line (^) until the last occurrence of the sequence : (colon followed by space) with the empty string (s/...// - substitute the first part with the second part, which is empty).

或

grep 'potato:' file.txt | cut -d   -f2

对于包含 potato: 的每一行，cut 会将行分割成多个由空格分隔的字段 (-d - d = delimiter, = 转义空格字符，类似 -d" " 也可以)并打印每行的第二个字段(-f2).

For each line that contains potato:, cut will split the line into multiple fields delimited by space (-d - d = delimiter, = escaped space character, something like -d" " would have also worked) and print the second field of each such line (-f2).

或

grep 'potato:' file.txt | awk '{print $2}'

对于包含 potato: 的每一行，awk 将打印第二个字段 (print $2)，默认情况下用空格分隔.

For each line that contains potato:, awk will print the second field (print $2) which is delimited by default by spaces.

或

grep 'potato:' file.txt | perl -e 'for(<>){s/^.*: //;print}'

所有包含 potato: 的行都被发送到内联 (-e) Perl 脚本，它采用 stdin，然后，对于每一行，做与上面第一个例子相同的替换，然后打印出来.

All lines that contain potato: are sent to an inline (-e) Perl script that takes all lines from stdin, then, for each of these lines, does the same substitution as in the first example above, then prints it.

或

awk '{if(/potato:/) print $2}' < file.txt

文件通过stdin发送(通过stdin发送文件内容到左边的命令) 到 awk 脚本，对于包含 potato: (if(/potato:/) 的每一行，如果正则表达式 /potato:/ 匹配当前行)，打印第二个字段，如上所述.

The file is sent via stdin (< file.txt sends the contents of the file via stdin to the command on the left) to an awk script that, for each line that contains potato: (if(/potato:/) returns true if the regular expression /potato:/ matches the current line), prints the second field, as described above.

或

perl -e 'for(<>){/potato:/ && s/^.*: // && print}' < file.txt

文件通过 stdin(，见上文)发送到一个 Perl 脚本，其工作方式与上述类似，但这次它也确保每一行都包含字符串 potato:(/potato:/ 是一个正则表达式，如果当前行包含 potato:，并且, 如果是 (&&)，则继续应用上述正则表达式并打印结果).

The file is sent via stdin (< file.txt, see above) to a Perl script that works similarly to the one above, but this time it also makes sure each line contains the string potato: (/potato:/ is a regular expression that matches if the current line contains potato:, and, if it does (&&), then proceeds to apply the regular expression described above and prints the result).

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