[bug #35668] odd behaviour with wildcard patterns accidently matching file names

[Eric Blake]

Update of bug #35668 (project grep):

                  Status:                    None => Invalid                
             Open/Closed:                    Open => Closed                 

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Follow-up Comment #1:

I'm closing this; it is not a bug in grep, but in your (mis-)use of the
shell.

~ $ echo -e "123n456" > test

echo -e is not portable.  POSIX recommends that you use printf(1) instead:

printf "123n456n" > test

~ $ cat test | grep [0-9][0-9][0-9]
123
456

Useless use of cat.

Missing shell quoting.  When you have no files that match the glob, then the
glob is passed through unchanged, so you are grepping for the pattern
'[0-9][0-9][0-9]'.

~ $ touch 456
~ $ cat test | grep [0-9][0-9][0-9]
456

Now that the glob matches, the shell expands it to the matching file name,
'456', so you are now grepping for the pattern '456'.

To see the difference, try:

echo [0-9][0-9][0-9]

both before and after creating one or more files with a 3-digit name.  What
you meant to do was:

grep '[0-9][0-9][0-9]' < test

Or, more compactly,

grep '[0-9]{3}' < test


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