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Re: How to enumerate files in a directory using the builtin shell?

From: Thiago Padilha
Subject: Re: How to enumerate files in a directory using the builtin shell?
Date: Fri, 29 Jan 2016 14:56:46 +0000

Jordan, thanks for the help

Unfortunately, the "insmod regexp" line is not working for me, at least not from the configuration file. This my grub.cfg:

    search.fs_uuid 1b3fdfe0-99cb-4aba-9acd-695b84be63cc btrfs hd0,gpt3
    set prefix=($btrfs)'/os/gubuntu-15.10/boot/grub'
    configfile $prefix/grub.cfg

(hd0,gpt3) is a btrfs partition with multiple subvolumes under the "os" directory, each containing a full  linux distro(with its own grub config) that I can boot to. In the above snippet, ubuntu gnome 15.10 is hardcoded, but I'd like to make this a bit more dynamic with something similar to the for/discover loop you suggested.

To test if the loop/discovery works in grub interactive shell, I did the following:

    search.fs_uuid 1b3fdfe0-99cb-4aba-9acd-695b84be63cc btrfs hd0,gpt3
    insmod regexp
    for os_path in ($btrfs)/os/*; do
      echo $os_path
      regexp --set=os_name '^\([^)]*\)/os/(.*)$' $os_path

Notice that I removed the configfile line to enter the interactive shell. I was expecting to see a list of distro names printed but nothing happens. Then I did: `echo $os_path` which printed `(hd0,gpt3)/os/*`(the glob didn't expand even with the `insmod regexp` module).

Normally I would assume that the regexp module wasn't available, but after typing `insmod regexp` in the interactive shell and running `echo $os_path` again I saw the expansion. What am I missing here?

On Fri, Jan 29, 2016 at 2:54 AM Jordan Uggla <address@hidden> wrote:
On Thu, Jan 28, 2016 at 5:56 PM, Thiago Padilha <address@hidden> wrote:
> I want to execute one "menuentry" command for each file in a directory.
> What's the best way to do it? In bash I would use something like `for file
> in $(ls); do`, but can't seem to find a way to use grub's `for` command.

You shouldn't try to parse the output of ls, even in bash:

For both grub and bash, to iterate over files you should use a for
loop with globs. The difference with grub being that you need to first
"insmod regexp" to enable globbing, for example:

insmod regexp # This is grub specific

# The following lines work exactly the same in bash and grub
for file in /boot-isos/*.iso; do
  echo found iso file "$file"

For a more complete real world example, the following grub script will
search for all files, on all devices/partitions, in a directory named
"/boot-isos/" and ending in ".iso" and will assume that they have a
loopback.cfg ( ). For
each iso found it will create an appropriate menuentry for booting the
iso using the loopback.cfg found within that iso:

insmod regexp
insmod all_video

for iso_with_device in (*)/boot-isos/*.iso; do

  # Remove the grub device name to get just the path to the iso
relative to its root.
  regexp --set=iso_path '^\(.*\)(.*$)' "$iso_with_device"

  menuentry "loop boot $iso_with_device" "$iso_path" {
    export iso_path
    search --set=root --file "$iso_path"
    loopback loop "$iso_path"
    configfile /boot/grub/loopback.cfg
    loopback --delete loop

Jordan Uggla (Jordan_U on

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