问题
The following command gives me a list of matching expressions:
grep -f /tmp/list Filename* > /tmp/output
The list file is then parsed and used to search Filename* for the parsed string. The results are then saved to output.
How would I output the parsed string from list in the case where there is no match in Filename*?
Contents of the list file could be:
ABC
BLA
ZZZ
HJK
Example Files:
Filename1:5,ABC,123
Filename2:5,ZZZ,342
Result of Running Command:
BLA
HJK
Stack overflow question 2480584 looks like it may be relevant, through the use of an if statement. However I'm not sure how to output the parsed string to the output file. Would require some type of read line?
TIA,
Mic
回答1:
This makes it:
$ grep -v "$(cat Filename* | cut -d, -f2)" /tmp/list
BLA
HJK
Explanation
$ cat Filename* | cut -d, -f2
ABC
ZZZ
And then grep -v looks for the inverse matching.
回答2:
Obviously, grep -f list Filename* gives all matches of patterns from the file list in the files specified by Filename*, i.e.,
Filename1:5,ABC,123
Filename2:5,ZZZ,342
in your example.
By adding the -o (only print matching expression) and -h (do not print filename) flags, we can turn this into:
ABC
ZZZ
Now you want all patterns from list that are not contained in this list, which can be achieved by
grep -f list Filename* -o -h | grep -f /dev/stdin -v list
where the second grep takes it's patterns from the output of the first and by using the -v flag gives all the lines of file list that do not match those patterns.
来源：https://stackoverflow.com/questions/18139306/listing-non-matching-entries-using-grep-f