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cmd: test: add bug-compatibility special case for 'test -n'

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It turns out that there is lots of code in the wild, including in the
U-Boot tree itself, which used to rely on

  test -n $somevar

to yield false when $somevar is not defined or empty. See for example
all the occurrences of 'test -n $fdtfile'. That was really only a
quirk of the implementation that refused calls with argc < 3, and not
because it was interpreted as

  test -n "$somevar"

which is how this should be spelled.

While not exactly conforming to POSIX, we can accomodate such scripts
by special-casing a single argument "-n" to be interpreted as if it
comes from code as above with empty $somevar.

Since we only just added the ability to test a string for emptiness
using the single-argument form, it is very unlikely that there is code
doing

  test "$str"

which would now fail if $str happens to be exactly "-n"; such a test
should really always be spelled

  test -n "$str"

Fixes: 8b0619579b ("cmd: test: fix handling of single-argument form of test")
Reported-by: Franz Schnyder <franz.schnyder@toradex.com>
Signed-off-by: Rasmus Villemoes <ravi@prevas.dk>
Reviewed-by: Simon Glass <sjg@chromium.org>
This commit is contained in:
Rasmus Villemoes
2026-03-30 16:01:06 +02:00
committed by Tom Rini
parent d1cd673391
commit f7e7c55e53
2 changed files with 22 additions and 1 deletions
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15
cmd/test.c
View File

@@ -75,12 +75,25 @@ static int do_test(struct cmd_tbl *cmdtp, int flag, int argc,
* Per POSIX, 'test' with 0 arguments should return 1, while
* 'test <arg>' should be equivalent to 'test -n <arg>',
* i.e. true if and only if <arg> is not empty.
*
* However, due to previous versions of U-Boot unconditionally
* returning false when 'test' was given less than two
* arguments, there are existing scripts that do
*
* test -n $somevar
*
* (i.e. without properly quoting $somevar) and expecting that
* to return false when $somevar expands to nothing. It is
* quite unlikely that anyone would use the single-argument
* form to test a string for being empty and a possible
* non-empty value for that string to be exactly "-n". So we
* interpret 'test -n' as if it was 'test -n ""'.
*/
if (argc < 2)
return 1;
if (argc == 2)
return !strcmp(argv[1], "");
return !strcmp(argv[1], "") || !strcmp(argv[1], "-n");
#ifdef DEBUG
{

8
test/hush/if.c
View File

@@ -41,6 +41,10 @@ static int hush_test_if_base(struct unit_test_state *uts)
sprintf(if_formatted, if_format, "test 'abc'");
ut_assertok(run_command(if_formatted, 0));
/* Special case: 'test -n' interpreted as 'test -n ""'. */
sprintf(if_formatted, if_format, "test '-n'");
ut_asserteq(1, run_command(if_formatted, 0));
return 0;
}
HUSH_TEST(hush_test_if_base, 0);
@@ -385,6 +389,10 @@ static int hush_test_lbracket_alias(struct unit_test_state *uts)
ut_asserteq(1, run_command(if_formatted, 0));
ut_assert_nextline(missing_rbracket_error);
/* Special case: '[ -n ]' interpreted as '[ -n "" ]'. */
sprintf(if_formatted, if_format, "[ -n ]");
ut_asserteq(1, run_command(if_formatted, 0));
return 0;
}
HUSH_TEST(hush_test_lbracket_alias, UTF_CONSOLE);