paul frith paul frith - 7 months ago 27
Bash Question

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:


  • MYFILE160418.dat

  • myFILE170312.DAT

  • MyFiLe160416.DaT



but not:


  • MYOTHERFILE150202.DAT

  • Myfile.dat

  • myfile.csv



Thanks,

Paul.

123 123
Answer

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.
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