CODEWITHSUNDEEP
regexbashshellunix
paul frith
paul frith

Reputation: 633

how to loop through files that match a regular expression in a unix shell script

I want to be able to loop through a list of files that match a particular pattern. I can get unix to list these files using ls and egrep with a regular expression, but I cannot find a way to turn this into an iterative process. I suspect that using ls is not the answer. Any help would be gratefully received.

My current ls command looks as follows:

ls | egrep -i 'MYFILE[0-9][0-9]([0][1-9]|1[0-2])([0][1-9]|[12][0-9]|[3][01]).dat'

I would expect the above to match:

but not:

Thanks,

Paul.

Upvotes: 16

Views: 23209

Answers (3)

gluttony
gluttony

Reputation: 569

I was looking for listing sda* and sdb* ending with one digit in /dev and I found that ls works by itself in this case:

> /dev/sd[ab][0-9]
/dev/sda1  /dev/sda2  /dev/sda3  /dev/sda4  /dev/sda5  /dev/sda6  /dev/sdb1

But there is a limitation that is it does not like the + character, if I want to search for example with several digit at end:

> ls /dev/sd[ab][0-9]+
ls: cannot access /dev/sd[ab][0-9]+: No such file or directory

And here you'll indeed need to use ls | egrep ... or find as other mentioned, but since in your regex you don't have a +, this should work for you:

ls MYFILE[0-9][0-9]([0][1-9]|1[0-2])([0][1-9]|[12][0-9]|[3][01]).dat

Upvotes: 0

paul frith
paul frith

Reputation: 633

Based on the link Andy K provided I have used the following to loop based on my matching criteria:

for i in $(ls | egrep -i 'MYFILE[0-9][0-9]([0][1-9]|1[0-2])([0][1-9]|[12][0-9]|[3][01]).dat' ); do             
 echo item: $i;         
done

Upvotes: 9

123
123

Reputation: 11216

You can use (GNU) find with the regex search option instead of parsing ls.

find . -regextype "egrep" \
       -iregex '.*/MYFILE[0-9][0-9]([0][1-9]|1[0-2])([0][1-9]|[12][0-9]|[3][01]).dat' \
       -exec [[whatever you want to do]] {} \;

Where [[whatever you want to do]] is the command you want to perform on the names of the files.

From the man page

-regextype type
          Changes  the regular expression syntax understood by -regex and -iregex tests 
          which occur later on the command line.  Currently-implemented types are 
          emacs (this is the default),posix-awk, posix-basic, posix-egrep and 
          posix-extended.

  -regex pattern
          File name matches regular expression pattern.  This is a match on the whole 
          path, not a search.  For example, to match a file named `./fubar3', you can 
          use the regular expression
          `.*bar.' or `.*b.*3', but not `f.*r3'.  The regular expressions understood by 
          find are by default Emacs Regular Expressions, but this can be changed with 
          the -regextype option.

  -iregex pattern
          Like -regex, but the match is case insensitive.

Upvotes: 10

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