linux shell CLI file get mime-type from a string variable

Question

I would like to detect an appropriate file extension in sh shell based on a content of a string variable. I tried to use for that file - manual

If I do:

echo "bar" > foo.txt
file foo.txt
file --mime-type foo.txt

then I get a valid result:

foo.txt: ASCII text
foo.txt: text/plain

but how to get the same result without creating a file and get content type?

I tried:

file <(echo 'bar')

and got:

/dev/fd/63: symbolic link to pipe:[1452271]

and with:

echo 'bar' | file

I got:

Usage: file [-bcCdEhikLlNnprsSvzZ0] [--apple] [--extension] [--mime-encoding]
            [--mime-type] [-e <testname>] [-F <separator>]  [-f <namefile>]
            [-m <magicfiles>] [-P <parameter=value>] [--exclude-quiet]
            <file> ...
       file -C [-m <magicfiles>]
       file [--help]

Is there any way to get with file:

foo.txt: ASCII text
foo.txt: text/plain

but without creating the file itself?

Perhaps I could use other app instead of file?

Answer 1

Try to use dash "-" argument of file.

Example 1:

file - <<< abc
/dev/stdin: ASCII text

Example 2:

echo abc | file - 
/dev/stdin: ASCII text

Example 3:

file - <<< '#!/bin/sh'
/dev/stdin: POSIX shell script, ASCII text executable

Example 4:

MY_VAR='#!/bin/awk'
file --mime-type - <<< $MY_VAR
/dev/stdin: text/x-awk