How can I match a string with a regex in Bash?

regex string bash
user1587462 picture user1587462 · Jul 2, 2013 · Viewed 306k times · Source

I am trying to write a bash script that contains a function so when given a .tar, .tar.bz2, .tar.gz etc. file it uses tar with the relevant switches to decompress the file.

I am using if elif then statements which test the filename to see what it ends with and I cannot get it to match using regex metacharacters.

To save constantly rewriting the script I am using 'test' at the command line, I thought the statement below should work, I have tried every combination of brackets, quotes and metacharaters possible and still it fails.

test sed-4.2.2.tar.bz2 = tar\.bz2$; echo $?
(this returns 1, false)

I'm sure the problem is a simple one and I've looked everywhere, yet I cannot fathom how to do it. Does someone know how I can do this?

Answer

dogbane picture dogbane · Jul 2, 2013

To match regexes you need to use the =~ operator.

Try this:

[[ sed-4.2.2.tar.bz2 =~ tar.bz2$ ]] && echo matched

Alternatively, you can use wildcards (instead of regexes) with the == operator:

[[ sed-4.2.2.tar.bz2 == *tar.bz2 ]] && echo matched

If portability is not a concern, I recommend using [[ instead of [ or test as it is safer and more powerful. See What is the difference between test, [ and [[ ? for details.

Related questions

bash, extract string before a colon

If I have a file with rows like this /some/random/file.csv:some string /some/random/file2.csv:some string2 Is there some way to get a file that only has the first part before the colon, e.g. /…

Read More
Bash need to test for alphanumeric string

Trying to verify that a string has only lowercase, uppercase, or numbers in it. if ! [[ "$TITLE" =~ ^[a-zA-Z0-9]+$ ]]; then echo "INVALID"; fi Thoughts? * UPDATE * The variable TITLE currently only has upper case text so it should pass and nothing should …

Read More
Check if string containts slash or backslash in Bash?

I'm currently trying to get my bash script checking if a string containts a "/" or a "\" but somehow I can't get it working. Here is what I got so far: if [[ "$1" == *\/* ]]; then ... elif if [[ "$1" == *\\* ]]; then ... fi Help is much appreciated! …

Read More