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.
The syntax to loop through each file individually in a loop is: create a variable (f for file, for example). Then define the data set you want the variable to cycle through. In this case, cycle through all files in the current directory using the * wildcard character (the * wildcard matches everything).
The grep (Global Regular Expression Print) is a unix command utility that can be used to find specific patterns described in “regular expressions”, a notation which we will learn shortly. For example, the “grep” command can be used to match all lines containing a specific pattern.
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.
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
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