Get content of wildcard/asterisk

Question

Is it possible to get the last content of a wildcard?

Let's say I have a list of files:

foo-15.csv
foo-32.csv
foo-65.csv

etc.

Is it possible to access the wildcard content when using:

for file in foo-*.csv; do
    echo wildcard_content
done

So that it prints

 15
 32
 65

note: I don't want to use string manipulation with $file. The above is a mere example and the globular expression could be anything. Is it possible to access the wildcard content? Is the wildcard content stored in a bash-defined variable that I can call, or something like that?

Answer 1

#! /bin/bash

shopt -s nullglob

for file in *.csv; do
    echo "${file%.csv}"
done

You can remove the .csv part like above.

You can understand the working of % from the docs.

It states:

${parameter%word}
${parameter%%word}
The word is expanded to produce a pattern and matched according to the rules described below (see Pattern Matching). If the pattern matches a trailing portion of the expanded value of parameter, then the result of the expansion is the value of parameter with the shortest matching pattern (the ‘%’ case) or the longest matching pattern (the ‘%%’ case) deleted. If parameter is ‘@’ or ‘’, the pattern removal operation is applied to each positional parameter in turn, and the expansion is the resultant list. If parameter is an array variable subscripted with ‘@’ or ‘’, the pattern removal operation is applied to each member of the array in turn, and the expansion is the resultant list.

@Sorin explained why to use shopt -s nullglob in comments. For further explanation, refer to the docs

Answer 2

I believe what you are after is something which resembles BASH_REMATCH.

An additional binary operator, =~, is available, with the same precedence as == and !=. When it is used, the string to the right of the operator is considered an extended regular expression and matched accordingly (as in regex(3)). The return value is 0 if the string matches the pattern, and 1 otherwise. If the regular expression is syntactical incorrect, the conditional expression's return value is 2. If the shell option nocasematch is enabled, the match is performed without regard to the case of alphabetic characters. Any part of the pattern may be quoted to force it to be matched as a string. Substrings matched by parenthesized subexpressions within the regular expression are saved in the array variable BASH_REMATCH. The element of BASH_REMATCH with index 0 is the portion of the string matching the entire regular expression. The element of BASH_REMATCH with index n is the portion of the string matching the nth parenthesized subexpression.

Unfortunately, glob patterns and regular expressions are not the same (See this question, and this linuxjournal article). Nonetheless, we can make a one-to-one translation:

|-------+-------+---------------------------------------|
| glob  | regex | remark                                |
|-------+-------+---------------------------------------|
| *     | [^/]* | filenames don't have a /              |
| **/   | .*/   | ** repreensts full paths (end with /) |
| ?     | [^/]  | filenames don't have a /              |
| [...] | [...] | the character groups are the same     |
|-------+-------+---------------------------------------|

You have to be careful though, as some characters have special meanings in regular expressions, but not in globular expressions. (Eg. ., +):

So in the example of the OP, you can do this:

for file in foo-*.csv; do
   [[ "${file}" =~ foo-([^/]*)[.]csv ]]
   echo "${BASH_REMATCH[1]}"
done

Or a more complicated example:

for file in *-substring-[0-3a-9]-foo?.file
     [[ "${file}" =~ ([^/]*)-substring-([0-3a-9])-foo(.)[.]file ]]
     echo "${BASH_REMATCH[1]} ${BASH_REMATCH[2]} ${BASH_REMATCH[3]}"
done

Answer 3

Similar to @Mihir answer but if you want to access the entire list of files per iteration then

files=(*.csv)
for file in "${files[@]}"; do
    echo ${files[@]//.csv/}
done