grep mistaking pattern for file?

cat file.txt | grep -x "\d*"
grep: \Documents and Settings: Is a directory

I want to search file.txt for any lines that are numbers only but grep seems to be viewing \d* as a wildcard for files and not the pattern. How can I specify that it's the pattern and it should use stdin for what to grep over?

The file is full of lines of datetime stamps, some end with a letter, some don't.


I'm trying to only get the lines that don't end in a letter.

EDIT: I've also tried setting the filename instead of piping it with cat. Not much different.

C:\long\path>grep -ex "\d*" -f file.txt
grep: \Dell: Is a directory
grep: \Documents and Settings: Is a directory


Why are you using cat to pass the file to grep? Why not just give grep the filename directly?

grep -x '\d*' file.txt

I think the actual problem you're seeing is that the * wildcard is being expanded. That's why grep is giving you errors that mention actual directories (beginning with 'd') on your system.

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