问题
I'm trying to list all entries in a directory whose names contain ONLY upper-case letters. Directories need "/" appended.
#!/bin/bash
cd ~/testfiles/
ls | grep -r *.*
Since grep by default looks for upper-case letters only (right?), I'm just recursively searching through the directories under testfiles for all names who contain only upper-case letters.
Unfortunately this doesn't work.
As for appending directories, I'm not sure why I need to do this. Does anyone know where I can start with some detailed explanations on what I can do with grep? Furthermore how to tackle my problem?
回答1:
No, grep does not only consider uppercase letters.
Your question I a bit unclear, for example:
- from your usage of the -r option, it seems you want to search recursively, however you don't say so. For simplicity I assume you don't need to; consider looking into @twm's answer if you need recursion.
- you want to look for uppercase (letters) only. Does that mean you don't want to accept any other (non letter) characters, but which are till valid for file names (like digits or dashes, dots, etc.)
- since you don't say th it i not permissible to have only on file per line, I am assuming it is OK (thus using
ls -1).
The naive solution would be:
ls -1 | grep "^[[:upper:]]\+$"
That is, print all lines containing only uppercase letters. In my TEMP directory that prints, for example:
ALLBIG
LCFEM
WPDNSE
This however would exclude files like README.TXT or FILE001, which depending on your requirements (see above) should most likely be included.
Thus, a better solution would be:
ls -1 | grep -v "[[:lower:]]\+"
That is, print all lines not containing an lowercase letter. In my TEMP directory that prints for example:
ALLBIG
ALLBIG-01.TXT
ALLBIG005.TXT
CRX_75DAF8CB7768
LCFEM
WPDNSE
~DFA0214428CD719AF6.TMP
Finally, to "properly mark" directories with a trailing '/', you could use the -F (or --classify) option.
ls -1F | grep -v "[[:lower:]]\+"
Again, example output:
ALLBIG
ALLBIG-01.TXT
ALLBIG005.TXT
CRX_75DAF8CB7768
LCFEM/
WPDNSE/
~DFA0214428CD719AF6.TMP
Note a different option would to be use find, if you can live with the different output (e.g. find ! -regex ".*[a-z].*"), but that will have a different output.
回答2:
The exact regular expression depend on the output format of your ls command. Assuming that you do not use an alias for ls, you can try this:
ls -R | grep -o -w "[A-Z]*"
note that with -R in ls you will recursively list directories and files under the current directory. The grep option -o tells grep to only print the matched part of the text. The -w options tell grep to consider as match only for whole words. The "[A-Z]*" is a regexp to filter only upper-cased words.
Note that this regexp will print TEST.txt as well as TEXT.TXT. In other words, it will only consider names that are formed by letters.
回答3:
It's ls which lists the files, not grep, so that is where you need to specify that you want "/" appended to directories. Use ls --classify to append "/" to directories.
grep is used to process the results from ls (or some other source, generally speaking) and only show lines that match the pattern you specify. It is not limited to uppercase characters. You can limit it to just upper case characters and "/" with grep -E '^[A-Z/]*$ or if you also want numbers, periods, etc. you could instead filter out lines that contain lowercase characters with grep -v -E [a-z].
As grep is not the program which lists the files, it is not where you want to perform the recursion. ls can list paths recursively if you use ls -R. However, you're just going to get the last component of the file paths that way.
You might want to consider using find to handle the recursion. This works for me:
find . -exec ls -d --classify {} \; | egrep -v '[a-z][^/]*/?$'
I should note, using ls --classify to append "/" to the end of directories may also append some other characters to other types of paths that it can classify. For instance, it may append "*" to the end of executable files. If that's not OK, but you're OK with listing directories and other paths separately, this could be worked around by running find twice - once for the directories and then again for other paths. This works for me:
find . -type d | egrep -v '[a-z][^/]*$' | sed -e 's#$#/#'
find . -not -type d | egrep -v '[a-z][^/]*$'
来源：https://stackoverflow.com/questions/14715387/listing-entries-in-a-directory-using-grep