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J. Doe
Asked: 2018-07-03 11:44:29 +0800 CST

Running a Bash while loop over all similar files

  • 772

I would like to write a while loop in Bash that runs over all instances of files that are of the form of 

{number}.tst

for example, 1.tst, 2.tst, ... 50.tst.

I do not want it to run over the file tst.tst.

How would I go about writing this? I assume I will need a boolean phrase and [0-9]* somewhere in there, but I am not entirely sure on the syntax.

scripts bash

4 Answers

  1. Best Answer

    If you only need to exclude alphabetic names like your example tst.tst you could use a simple shell glob

    for f in [0-9]*.tst; do echo "$f"; done

    With bash extended globs (which should be enabled by default in Ubuntu)

    given

    $ ls *.tst
1.tst  2.tst  3.tst  4.tst  50.tst  5.tst  bar.tst  foo.tst

    then +([0-9]) means one or more decimal digits:

    for f in +([0-9]).tst; do echo "$f"; done
1.tst
2.tst
3.tst
4.tst
50.tst
5.tst

    You can check whether extended globbing is enabled using shopt extglob and set it if necessary using shopt -s extglob (and unset using set -u extglob).

    • 9

  2. From this Stack Overflow answer: List files that only have number in names:

    find . -regex '.*/[0-9]+\.tst'

    OR

    Using find also has advantages when you want to do something with the files, e.g. using the built-in -exec, -print0 and pipe to xargs -0 or even (using Bash):

    while IFS='' read -r -d '' file
do
  # ...
done < <(find . -regex '.*/[0-9]+\.tst' -print0)

    Note the other answers here my include files that aren't numbers if the filename starts with a digit. The answer posted here does not though. For example:

    $ ls *.tst
12tst.tst  1.tst  2.tst

$ find . -maxdepth 1 -regex '.*/[0-9]+\.tst'
./1.tst
./2.tst

    NOTE: Use -maxdepth 1 argument to only list numbered files in the current directory and not in sub-directories.

    • 6

  3. In this case, there are no filenames of the form {number}{non-number}.tst, so one possible solution is to include all the filenames that start with a number:

    for filename in [0-9]*.tst; do
    echo "$filename"  # Example command
done
    • 4

  4. If you want to process the files in numerical order, there's the seq command (read man seq).

    for i in $( seq 1 50 ) ; do
    echo "Process ${i}.txt"
done
    • 0