awk检查文件存在 [英] awk check file exists

问题描述

printf "2015-03-02|/home/user/.ssh/config\n2015-03-02|/home/user/Desktop/temp328\n" | awk -F\| 'if ( -f $2 )  { print $2}'

或

printf "2015-03-02|/home/user/.ssh/config\n2015-03-02|/home/user/Desktop/temp328\n" | awk -F\| '{if (system("test -f" $2)) print $2}'

/home/user/.ssh/config\n2015-03-02-存在

/home/user/.ssh/config\n2015-03-02 - exists

/home/user/Desktop/temp328-已删除

/home/user/Desktop/temp328 - removed

我只想打印现有文件，但是此命令不起作用.

I want print only exist files but this commands not working.

推荐答案

第二次尝试非常接近.在test -f之后需要一个空格.

The second attempt was fairly close; you need a space after the test -f.

base$ echo '2015|/etc/mtab
> 2015|/etc/ntab' | awk -F\| '{ if (system("test -f " $2)) print $2}'
/etc/ntab

您可能想要反转使用if (system(...)==0)来获得所需的语义.另外，稍微优雅一点的是，Awk想要在括号之外使用一个条件，因此您可以避免使用显式的if.

You probably want to invert to use if (system(...)==0) to get the semantics you expected. Also, somewhat more elegantly, Awk wants a condition outside the braces, so you can avoid the explicit if.

awk -F\| 'system("test -f " $2)==0 { print $2 }'

同意评论者的意见，认为使用Awk只是边缘问题.

Agree with commenters that using Awk for this is borderline nuts.

如果如注释中所示，如果您需要使用完全任意的文件名，则可以添加代码以引用任何特殊的shell:

If, as indicated in comments, you need to work with completely arbitrary file names, you can add code to quote any shell specials:

awk -F\| 'system ("test -f " gensub(/[^\/A-Za-z0-9]/, "\\\\&", "g", $2))==0 {
   print $2 }'   # caveat: gensub() is gawk only

...但是您的整体解决方案无法处理包含换行符或管道符的文件名(因为分别将它们用作记录分隔符和字段分隔符)，因此再次放弃Awk并以另一种方法重新开始可能是前进的明智之路.

... but your overall solution does not cope with file names containing a newline character or a pipe character (since you are using those as record and field separators, respectively) so again, abandoning Awk and starting over with a different approach may be the sane way forward.

(替换中的字符类不完整；可以添加各种标点符号等，我可能遗漏了一些重要内容；但是在快速检查时，多余的反斜杠应该是无害的.如果您没有Gawk，请参见此处，和/或再次考虑放弃这种方法.)

(The character class in the substitution is incomplete; there are various punctuation characters etc which could be added, and I may be missing something significant; but on quick examination, the superfluous backslashes should be harmless. If you don't have Gawk, see here and/or, again, consider abandoning this approach.)

while IFS='|' read -r stuff filename; do
    test -f "$filename" && echo "$filename"
done <<':'
2015|/etc/mtab
2016|/etc/ntab
2017|/path/to/file with whitespace in name
2018|/path/to/file\with[funny"characters*in(file'name|even pipes, you see?
:

(仍然没有换行符，但是其他都应该没问题.)

(Still no way to have a newline, but everything else should be fine.)

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