Bash extended glob – match files without prefix

bashbash-expansionwildcards

I'm trying to match filenames for a fail2ban jail – so I need to use filename globbing only – not regexes or bash scripting.

My /var/log/apache2 directory contains files including:

example.com.error.log
db.example.com.error.log
app1.example.com.error.log
app2.example.com.error.log

I'm trying to create a glob to match all files ending in .error.log except db.example.error.log – is this possible?

I've tried !(db)*.error.log but this still matches db.example.com.error.log. I'm guessing the !() is matching no characters, allowing the * to match from the beginning of the filename.

Note: I don't want to have to extend the glob when new appX logfiles are added, so I can't use @() with the list of currently-known non-db filenames.

(Background: I want to create a filter banning anyone requesting any phpMyAdmin URLs on any domain except db.example.com)

Best Answer

The extended filename globbing pattern (supported by bash with the extglob shell option activated, and also by ksh93)

!(db*).error.log

will ignore anything that starts with db.

To be more specific:

!(db.example.com).error.log

This will ignore any name in the current directory that starts with exactly db.example.com.

The !(db.example.com) pattern acts like a "special *" that will not match the the string db.example.com.

Your pattern,

!(db)*.error.log

excludes any name that starts with db, but allows any string after that, which obviously includes db.

By the same analogy as above, !(db) acts "like *" but won't match the exact string db, leaving us with the pattern **.error.log so to speak (with the first * being "special").

Related Solutions

Bash Wildcards – How to Exclude One Pattern from Glob Match

shopt -s extglob
echo rm foo.!(org)

This is "foo." followed by anything NOT "org"

ref: https://www.gnu.org/software/bash/manual/bashref.html#Pattern-Matching

Bash – Guide to Extended Globbing

Bash has no feature to expand just one match out of many.

The pattern @(foo) matches just one occurrence of the pattern foo. That is, it matches foo, but not foofoo. This syntactic form is useful to build or patterns like @(foo|bar), which matches either foo or bar. It can be used as part of longer patterns like @(foo|bar)-*.txt, which matches foo-hello.txt, foo-42.txt, bar-42.txt, etc.

If you want to use one match among many, you can put the matches in an array, and then use an element of the array.

kernels=(vmlinuz*)
ls -l "${kernels[0]}"

Matches are always sorted in lexicographic order, so this will print the first match in lexicographic order.

Note that if the pattern doesn't match any file, you'll get an array containing a single element which is the unchanged pattern:

$ a=(doesnotmatchanything*)
$ ls -l "${a[0]}"
ls: cannot access doesnotmatchanything*: No such file or directory

Set the nullglob option to get an empty array instead.

shopt -s nullglob
kernels=(vmlinuz*)
if ((${#kernels[@]} == 0)); then
  echo "No kernels here"
else
  echo "One of the ${#kernels[@]} kernels is ${kernels[0]}"
fi

Zsh has convenient features here. The glob qualifier [NUM] causes the pattern to expand to only the NUMth match; the variant [NUM1,NUM2] expands to the NUM1th through NUM2th matches (starting at 1).

% ls -l vmlinuz*([1])
lrwxrwxrwx 1 root root 26 Nov 15 21:12 vmlinuz -> vmlinuz-3.16-0.bpo.3-amd64
% ls -l nosuchfilehere*([1])
zsh: no matches found: nosuchfilehere*([1])

The glob qualifier N causes the pattern to expand to an empty list if no file is matched.

kernels=(vmlinuz*(N))
if ((#kernels)); then
  ls -l $kernels
else
  echo "No kernels here"
fi

The glob qualifier om sorts matches by increasing age instead of by name (m is for modification time); Om sorts by decreasing age . So vmlinuz*(om[1]) expands to the most recent kernel file.

Best Answer

Related Solutions

Bash Wildcards – How to Exclude One Pattern from Glob Match

Bash – Guide to Extended Globbing

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