Using regex in bash to find files

Question

Basically what I am trying to do is list the contents of the current directory that has a certain extension (in my case .c files).

So what I thought would work is:

ls | grep .\*\.c

And it mainly works but also returns files that end in c like

music (which is a directory)
test.doc

Is there a problem with my regex because I cannot see it.

Many Thanks

Andrew Logvinov · Accepted Answer · 2012-12-12 17:53:15Z

5

You can simply use ls *.c to list all files in the current directory having .c extension.

answered Dec 12, 2012 at 17:53

Andrew Logvinov

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1 Comment

djjavo Over a year ago

thanks for that andrew - did not know this. sorry if i wasn't clear in the question, but i would prefer to use ls | grep. many thanks for the help though, it is much appreciated :)

sampson-chen · Accepted Answer · 2012-12-12 18:00:44Z

4

Here's what you can do:

find -name "*.c"

and it will find all files with the .c extension for you, recursively from the current working directory.

Alternatively, if you want non-recursive and want to do it with ls, you can do:

ls *.c

If you want to know how to apply regex with grep to a ls search result (even though this is more cumbersome):

ls | grep ".*\.c$"

Regexplanation:

. - match any character
.* - match any character zero or more times
.*\. - match any character zero or more times, then match a . literally (specified by "escaping" it with \)
".*\.c - match any character zero or more times, then match a . literally, then match the char c
.*\.c$ - match any character zero or more times, then match a . literally, then match the char c; and only if that is the end of the pattern (there are no more things after that). $ is the regex anchor for "the end".

edited Dec 12, 2012 at 18:00

answered Dec 12, 2012 at 17:53

sampson-chen

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1 Comment

Julien May Over a year ago

to mention that find searches recursively.

Julien May · Accepted Answer · 2012-12-12 17:57:50Z

2

you are pretty close

ls | grep \\.c$

see the double backslashs

answered Dec 12, 2012 at 17:57

Julien May

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Comments

mVChr · Accepted Answer · 2012-12-12 17:59:49Z

1

You need to escape your backslash:

ls | grep .*\\.c

answered Dec 12, 2012 at 17:59

mVChr

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8 Comments

djjavo Over a year ago

many thanks for this. works perfectly. may i ask why you need to escape the backslash? from my understanding that regex means 0 or more of anything followed by \ followed by one of anything followed by c. Am I missing something here!

mVChr Over a year ago

@djjavo normally in bash a backslash means "escape the next character", so to use an actual backslash for your regex you need to escape it.

djjavo Over a year ago

yes i understand the \ being the escape character but i do not understand why we need to use an actual backslash in the regular expression (as its somecode.c not somecode\.c) am i being stupid because i do not understand!?

Drake Clarris Over a year ago

in regular expressions, a . matches any character, so you have to escape the . to match an actual .

djjavo Over a year ago

yes i know that, but is you have "\\" then you are escaping the escape character??

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