第一列中有空格的awk输出

Question

我试着用awk分割列来打印一个句子，但是第一个列有空格。

我的初学者代码示例：

$ awk '/Linux/ { print "The filename","\""$1"\"","is located in",$2 }' test.txt
The filename "The" is located in test
The filename "Some" is located in file
The filename "File" is located in name
The filename "Something_here" is located in /ABC
The filename "Another_test" is located in /DEFG
The filename "Label" is located in test

From : test.txt

Filename                               Folder         Type
-------------------------------------- -------------- ------
The test file                          /test/folder   Linux
Some file                              /              Linux
File name                              /Temp          Linux
Something_here                         /ABC           Linux
Another_test                           /DEFG          Linux
Label test                             /HIJK          Linux 

我想要达到的目标：(含引号)

The filename "Default file" is located in / 
The filename "The test file" is located in /test/folder

问题是当我使用'space‘或'/’作为分隔符时，在打印时不能得到整行

Answer 1

如果您有GNU AWK，这应该可以做到：

awk 'match($0, /([^\/]+)([^ ]+) *Linux/, arr) { sub(/ +$/, "", arr[1]); printf("The filename \"%s\" is located in %s\n", arr[1], arr[2]) }' test.txt

解释：

# match and store groups in 'arr'
#  - arr[1]: everything up until the first slash (including a lot of whitespace)
#  - arr[2]: first slash until space
#  - rest: also ensure there's 'Linux' after that
match($0, /([^\/]+)([^ ]+) *Linux/, arr) {

  # trim whitespace from the right hand side of the filename
  sub(/ +$/, "", arr[1]);

  # print
  printf("The filename \"%s\" is located in %s\n", arr[1], arr[2])
}

请注意，在其他版本的AWK中，也有一个功能较弱的match版本，使用这些版本也可以实现相同的功能，但是您必须编写更多的代码。

Answer 2

我建议使用基于正则表达式和反向引用的替换，加上一个sed命令，以消除源文件的头行：

$ cat test.txt | grep -E 'Linux[ ]*$' | sed -E 's%(.+)([^ ])([ ]+)(/.+)[ ]+Linux[ ]*$%The filename "\1\2" is located in \4%'
The filename "The test file" is located in /test/folder  
The filename "Some file" is located in /             
The filename "File name" is located in /Temp         
The filename "Something_here" is located in /ABC          
The filename "Another_test" is located in /DEFG         
The filename "Label test" is located in /HIJK

正则表达式(regex)的一个很好的引用在Linux手册中。

评论中所要求的详细说明：

• grep和-E选项接受扩展正则表达式(上面的参考文档)。在这里，它用于过滤包含"Linux“字的行，并在每一行末尾加上一些空格(如果有的话)。
• grep的输出进入sed的输入。
• sed被传递-E选项(如grep )以接受扩展正则表达式。的命令替换了与regex匹配的字符(% chars = "(.+ )( ^ )( +)(/.+) +Linux *$“之间的第一部分)(在% chars =”文件名“\1\2中的第二部分位于\4中)。
• 第二部分使用反向引用：'\‘后面跟着一个非零十进制数字n，由正则表达式的nth括号子表达式代替。在这里，\1被与这里的文件名第1 "(.+)“匹配的字符串替换，\2被以下的"(^ )”所替代，该字符串是文件名的最后一个字符(从名称中消除以下空格的技巧).

这并不是一个严格的解释，但至少它提供了一些进一步的投入。

另一种解决方案是在sed命令行上传递多个操作。因此，您可以添加一个查询来删除前两个头行，以便使用cat和grep来抑制管道。此处“1，2d”意为“删除第1和第2行”：

$ sed -E '1,2d;s%(.+)([^ ])([ ]+)(/.+)[ ]+Linux[ ]*$%The filename "\1\2" is located in \4%' test.txt
The filename "The  test file" is located in /test/folder  
The filename "Some file" is located in /             
The filename "File name" is located in /Temp         
The filename "Something_here" is located in /ABC          
The filename "Another_test" is located in /DEFG         
The filename "Label test" is located in /HIJK

注意:根据手册，-E选项切换到使用扩展正则表达式。多年来，GNU sed一直支持它，现在已包含在POSIX中。在旧系统上，如果不支持-r，则可以使用-E：

$ sed -r '1,2d;s%(.+)([^ ])([ ]+)(/.+)[ ]+Linux[ ]*$%The filename "\1\2" is located in \4%' test.txt
The filename "The  test file" is located in /test/folder  
The filename "Some file" is located in /             
The filename "File name" is located in /Temp         
The filename "Something_here" is located in /ABC          
The filename "Another_test" is located in /DEFG         
The filename "Label test" is located in /HIJK

Answer 3

GNU awk有regex字段分隔符，因此只需要分隔列的多个空格即可。

awk '/Linux/ { print "The file \""$1"\" is in "$2"." }' FS="   *" test.txt

info gawk fieldwidths说，它还提供了固定宽度的字段，您可以使用破折号线的长度来设置动态字段。