模式后如何grep内容? [英] How to grep for contents after pattern?

问题描述

给出一个文件，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表示，但仅使用管道传输potato:之后的数字.因此，在上面的示例中，输出为:

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 查找包含字符串的任何行potato:，那么对于每行， sed 用空字符串(s///-替换)从行(^)开始到最后出现的序列:(冒号后跟空格)的任何字符(.*) >-将第一部分替换为第二部分(空白).

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 会将行拆分为多个由空格分隔的字段(-d\-d =定界符，\ =转义的空格字符，例如-d" "也会起作用)，并打印每行这样的第二个字段( -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 将显示第二个字段(print $2)，默认情况下用空格定界.

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，该脚本需要 stdin 中的所有行，然后，对于每行，进行与上述第一个示例相同的替换，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

通过stdin发送文件(< file.txt通过stdin将文件内容发送到左侧的命令)到awk脚本，该脚本针对包含potato:的每一行(<如果正则表达式/potato:/与当前行匹配，则c28>返回true)，如上所述，打印第二个字段.

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

该文件通过stdin(< file.txt，请参见上文)发送到一个Perl脚本，该脚本的工作方式与上面的类似，但是这次还确保了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:则匹配，如果正则表达式(&&)匹配，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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