Regular Expressions for file name matching

In Bash, how does one match a regular expression with multiple criteria against 开发者_如何学运维a file name? For example, I'd like to match against all the files with .txt or .log endings.

I know how to match one type of criteria:

for file in *.log
do
        echo "${file}"
done

What's the syntax for a logical or to match two or more types of criteria?

Bash does not support regular expressions per se when globbing (filename matching). Its globbing syntax, however, can be quite versatile. For example:

for i in A*B.{log,txt,r[a-z][0-9],c*} Z[0-5].c; do
...
done

will apply the loop contents on all files that start with A and end in a B, then a dot and any of the following extensions:

• log
• txt
• r followed by a lowercase letter followed by a single digit
• c followed by pretty much anything

It will also apply the loop commands to an file starting with Z, followed by a digit in the 0-5 range and then by the .c extension.

If you really want/need to, you can enable extended globbing with the shopt builtin:

shopt -s extglob

which then allows significantly more features while matching filenames, such as sub-patterns etc.

See the Bash manual for more information on supported expressions:

http://www.gnu.org/software/bash/manual/bash.html#Pattern-Matching

EDIT:

If an expression does not match a filename, bash by default will substitute the expression itself (e.g. it will echo *.txt) rather than an empty string. You can change this behaviour by setting the nullglob shell option:

shopt -s nullglob

This will replace a *.txt that has no matching files with an empty string.

EDIT 2:

I suggest that you also check out the shopt builtin and its options, since quite a few of them affect filename pattern matching, as well as other aspects of the the shell:

http://www.gnu.org/software/bash/manual/bash.html#The-Shopt-Builtin

Do it the same way you'd invoke ls. You can specify multiple wildcards one after the other:

for file in *.log *.txt

for file in *.{log,txt} ..

for f in $(find . -regex ".*\.log")
do 
  echo $f
end

You simply add the other conditions to the end:

for VARIABLE in 1 2 3 4 5 .. N
do
    command1
    command2
    commandN
done

So in your case:

for file in *.log *.txt
do
        echo "${file}"
done

You can also do this:

shopt -s extglob
for file in *.+(log|txt)

which could be easily extended to more alternatives:

for file in *.+(log|txt|mp3|gif|foo)