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

[Jordan Uggla]

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:
http://mywiki.wooledge.org/BashPitfalls#for_i_in_.24.28ls_.2A.mp3.29

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"
done

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 ( http://www.supergrubdisk.org/wiki/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" {
    iso_path="$2"
    export iso_path
    search --set=root --file "$iso_path"
    loopback loop "$iso_path"
    root=(loop)
    configfile /boot/grub/loopback.cfg
    loopback --delete loop
  }
done

-- 
Jordan Uggla (Jordan_U on irc.freenode.net)