* [PATCH] commands: readlink: restore support for non-existent last component
@ 2026-01-26 10:52 Ahmad Fatoum
2026-01-27 7:46 ` Sascha Hauer
0 siblings, 1 reply; 2+ messages in thread
From: Ahmad Fatoum @ 2026-01-26 10:52 UTC (permalink / raw)
To: barebox; +Cc: Ahmad Fatoum, Ian Abbott, Claude Sonnet 4.5
The documentation and commit a6f379599227 ("readlink: Improve -f handling") hint
that the last component missing used to not be an error. This is not the
case currently, so restore the original behavior and add an -e option
for the current behavior of all components existing.
To ensure this doesn't regress in future, also add some AI-generated
test cases.
Cc: Ian Abbott <abbotti@mev.co.uk>
Co-developed-by: Claude Sonnet 4.5 <noreply@anthropic.com>
Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
---
commands/Kconfig | 7 +-
commands/readlink.c | 66 ++++++++---
test/py/test_shell_readlink.py | 202 +++++++++++++++++++++++++++++++++
3 files changed, 256 insertions(+), 19 deletions(-)
create mode 100644 test/py/test_shell_readlink.py
diff --git a/commands/Kconfig b/commands/Kconfig
index 297c89b4b566..e7de951005f4 100644
--- a/commands/Kconfig
+++ b/commands/Kconfig
@@ -1161,14 +1161,17 @@ config CMD_READLINK
help
Read value of a symbolic link
- Usage: readlink [-f] FILE [VARIABLE]
+ Usage: readlink [-fe] FILE [VARIABLE]
Read value of a symbolic link or canonical file name
The value is either stored it into the specified VARIABLE
or printed.
Options:
- -f canonicalize by following first symlink
+ -f canonicalize by following symlinks
+ final component need not exist
+ -e canonicalize by following symlinks
+ all components must exist
config CMD_RM
tristate
diff --git a/commands/readlink.c b/commands/readlink.c
index a37b6d7512d7..021fbaa3e08b 100644
--- a/commands/readlink.c
+++ b/commands/readlink.c
@@ -11,6 +11,8 @@
#include <malloc.h>
#include <getopt.h>
+enum can_mode { CAN_NONE, CAN_ALL_BUT_LAST, CAN_EXISTING };
+
static void output_result(const char *var, const char *val)
{
if (var)
@@ -20,20 +22,59 @@ static void output_result(const char *var, const char *val)
}
+static int canonicalize_filename_mode(const char *var, char *path, enum can_mode can_mode)
+{
+ char *buf = NULL, *file, *dir;
+ struct stat s;
+ int ret = -1;
+
+ buf = canonicalize_path(AT_FDCWD, path);
+ if (buf)
+ goto out;
+
+ switch (can_mode) {
+ case CAN_ALL_BUT_LAST:
+ file = basename(path);
+ dir = dirname(path);
+
+ buf = canonicalize_path(AT_FDCWD, dir);
+ if (!buf || stat(dir, &s) || !S_ISDIR(s.st_mode))
+ goto err;
+
+ buf = xrasprintf(buf, "/%s", file);
+ break;
+ case CAN_EXISTING:
+ case CAN_NONE:
+ goto err;
+ }
+
+out:
+ output_result(var, buf);
+ ret = 0;
+err:
+ free(buf);
+ return ret;
+}
+
static int do_readlink(int argc, char *argv[])
{
const char *var;
char *path, realname[PATH_MAX];
- int canonicalize = 0;
+ enum can_mode can_mode = CAN_NONE;
int opt;
memset(realname, 0, PATH_MAX);
- while ((opt = getopt(argc, argv, "f")) > 0) {
+ while ((opt = getopt(argc, argv, "fe")) > 0) {
switch (opt) {
case 'f':
- canonicalize = 1;
+ can_mode = CAN_ALL_BUT_LAST;
break;
+ case 'e':
+ can_mode = CAN_EXISTING;
+ break;
+ default:
+ return COMMAND_ERROR_USAGE;
}
}
@@ -46,18 +87,9 @@ static int do_readlink(int argc, char *argv[])
path = argv[0];
var = argv[1];
- if (canonicalize) {
- char *buf = canonicalize_path(AT_FDCWD, path);
- struct stat s;
-
- if (!buf)
+ if (can_mode > CAN_NONE) {
+ if (canonicalize_filename_mode(var, path, can_mode))
goto err;
- if (stat(dirname(path), &s) || !S_ISDIR(s.st_mode)) {
- free(buf);
- goto err;
- }
- output_result(var, buf);
- free(buf);
} else {
if (readlink(path, realname, PATH_MAX - 1) < 0)
goto err;
@@ -77,14 +109,14 @@ BAREBOX_CMD_HELP_TEXT("The value is either stored it into the specified VARIABLE
BAREBOX_CMD_HELP_TEXT("or printed.")
BAREBOX_CMD_HELP_TEXT("")
BAREBOX_CMD_HELP_TEXT("Options:")
-BAREBOX_CMD_HELP_OPT("-f", "canonicalize by following symlinks;")
-BAREBOX_CMD_HELP_OPT("", "final component need not exist");
+BAREBOX_CMD_HELP_OPT("-f", "canonicalize by following symlinks; final component need not exist")
+BAREBOX_CMD_HELP_OPT("-e", "canonicalize by following symlinks; all components must exist")
BAREBOX_CMD_HELP_END
BAREBOX_CMD_START(readlink)
.cmd = do_readlink,
BAREBOX_CMD_DESC("read value of a symbolic link or canonical file name")
- BAREBOX_CMD_OPTS("[-f] FILE [VARIABLE]")
+ BAREBOX_CMD_OPTS("[-fe] FILE [VARIABLE]")
BAREBOX_CMD_GROUP(CMD_GRP_FILE)
BAREBOX_CMD_HELP(cmd_readlink_help)
BAREBOX_CMD_END
diff --git a/test/py/test_shell_readlink.py b/test/py/test_shell_readlink.py
new file mode 100644
index 000000000000..ccd8ccfec421
--- /dev/null
+++ b/test/py/test_shell_readlink.py
@@ -0,0 +1,202 @@
+# SPDX-License-Identifier: GPL-2.0-only
+
+from .helper import skip_disabled
+
+
+def test_cmd_readlink(barebox, barebox_config):
+ skip_disabled(barebox_config, "CONFIG_CMD_READLINK", "CONFIG_CMD_MKDIR")
+
+ # Create test directory structure
+ barebox.run_check('mkdir -p /tmp/readlink-test/subdir')
+ barebox.run_check('cd /tmp/readlink-test')
+
+ stdout = barebox.run_check('readlink -f .')
+ assert stdout == ["/tmp/readlink-test"]
+
+ # Test relative path resolution
+ stdout = barebox.run_check('readlink -f ./subdir')
+ assert stdout == ["/tmp/readlink-test/subdir"]
+
+ # Test with variable storage
+ stdout = barebox.run_check('readlink -f ./subdir mypath && echo $mypath')
+ assert stdout == ["/tmp/readlink-test/subdir"]
+
+ stdout = barebox.run_check('readlink -f ./subdir/something mypath && echo $mypath')
+ assert stdout == ["/tmp/readlink-test/subdir/something"]
+
+ # Test with variable storage (positional argument)
+ stdout = barebox.run_check('readlink -f subdir mypath && echo $mypath')
+ assert stdout == ["/tmp/readlink-test/subdir"]
+
+ # Test with absolute path (should return as-is)
+ stdout = barebox.run_check('readlink -f /tmp')
+ assert stdout == ["/tmp"]
+
+ # Cleanup
+ barebox.run_check('rm -r /tmp/readlink-test')
+
+
+def test_cmd_readlink_nonexistent(barebox, barebox_config):
+ skip_disabled(barebox_config, "CONFIG_CMD_READLINK", "CONFIG_CMD_MKDIR")
+
+ # Create test directory structure
+ barebox.run_check('mkdir -p /tmp/readlink-test2/existing')
+ barebox.run_check('cd /tmp/readlink-test2')
+
+ # Test -f with non-existent final component (should work)
+ stdout = barebox.run_check('readlink -f existing/nonexistent')
+ assert stdout == ["/tmp/readlink-test2/existing/nonexistent"]
+
+ # Test -f with nested non-existent final component
+ stdout = barebox.run_check('readlink -f ./existing/also-nonexistent')
+ assert stdout == ["/tmp/readlink-test2/existing/also-nonexistent"]
+
+ # Test -e with non-existent final component (should fail)
+ _, _, returncode = barebox.run('readlink -e existing/nonexistent')
+ assert returncode != 0
+
+ # Test -e with existing component (should work)
+ stdout = barebox.run_check('readlink -e existing')
+ assert stdout == ["/tmp/readlink-test2/existing"]
+
+ # Test -f with non-existent parent directory (should fail)
+ _, _, returncode = barebox.run('readlink -f nonexistent-parent/file')
+ assert returncode != 0
+
+ # Test -e with non-existent parent directory (should fail)
+ _, _, returncode = barebox.run('readlink -e nonexistent-parent/file')
+ assert returncode != 0
+
+ # Cleanup
+ barebox.run_check('rm -r /tmp/readlink-test2')
+
+
+def test_cmd_readlink_symlinks(barebox, barebox_config):
+ skip_disabled(barebox_config, "CONFIG_CMD_READLINK", "CONFIG_CMD_MKDIR", "CONFIG_CMD_LN", "CONFIG_CMD_ECHO")
+
+ # Create test directory structure with symlinks
+ barebox.run_check('mkdir -p /tmp/readlink-test3/real/deep')
+ barebox.run_check('cd /tmp/readlink-test3')
+ barebox.run_check('echo -o real/file.txt content')
+
+ # Create various symlinks
+ barebox.run_check('ln real link-to-real')
+ barebox.run_check('ln real/file.txt link-to-file')
+ barebox.run_check('ln link-to-real link-to-link')
+ barebox.run_check('ln nonexistent broken-link')
+
+ # Test basic readlink (no -f/-e, just read symlink value)
+ stdout = barebox.run_check('readlink link-to-real')
+ assert stdout == ["real"]
+
+ stdout = barebox.run_check('readlink link-to-file')
+ assert stdout == ["real/file.txt"]
+
+ # Test -f following single symlink
+ stdout = barebox.run_check('readlink -f link-to-real')
+ assert stdout == ["/tmp/readlink-test3/real"]
+
+ stdout = barebox.run_check('readlink -f link-to-file')
+ assert stdout == ["/tmp/readlink-test3/real/file.txt"]
+
+ # Test -f following multiple levels of symlinks
+ stdout = barebox.run_check('readlink -f link-to-link')
+ assert stdout == ["/tmp/readlink-test3/real"]
+
+ # Test -e following symlinks (should work when target exists)
+ stdout = barebox.run_check('readlink -e link-to-real')
+ assert stdout == ["/tmp/readlink-test3/real"]
+
+ stdout = barebox.run_check('readlink -e link-to-file')
+ assert stdout == ["/tmp/readlink-test3/real/file.txt"]
+
+ # Test -e with broken symlink (should fail)
+ _, _, returncode = barebox.run('readlink -e broken-link')
+ assert returncode != 0
+
+ # Test -f with broken symlink (canonicalizes the link path itself)
+ stdout = barebox.run_check('readlink -f broken-link')
+ assert stdout == ["/tmp/readlink-test3/broken-link"]
+
+ # Test -f with symlink to non-existent file in existing subdirectory
+ barebox.run_check('ln real/nonexistent link-to-nonexistent')
+ stdout = barebox.run_check('readlink -f link-to-nonexistent')
+ assert stdout == ["/tmp/readlink-test3/link-to-nonexistent"]
+
+ # Test -e with symlink to non-existent file (should fail)
+ _, _, returncode = barebox.run('readlink -e link-to-nonexistent')
+ assert returncode != 0
+
+ # Cleanup
+ barebox.run_check('rm -r /tmp/readlink-test3')
+
+
+def test_cmd_readlink_parent_refs(barebox, barebox_config):
+ skip_disabled(barebox_config, "CONFIG_CMD_READLINK", "CONFIG_CMD_MKDIR")
+
+ # Create test directory structure
+ barebox.run_check('mkdir -p /tmp/readlink-test4/a/b/c')
+ barebox.run_check('cd /tmp/readlink-test4/a/b/c')
+
+ # Test parent directory references with -f
+ stdout = barebox.run_check('readlink -f ..')
+ assert stdout == ["/tmp/readlink-test4/a/b"]
+
+ stdout = barebox.run_check('readlink -f ../..')
+ assert stdout == ["/tmp/readlink-test4/a"]
+
+ stdout = barebox.run_check('readlink -f ../../..')
+ assert stdout == ["/tmp/readlink-test4"]
+
+ # Test parent with additional path components
+ stdout = barebox.run_check('readlink -f ../../../a/b')
+ assert stdout == ["/tmp/readlink-test4/a/b"]
+
+ # Test -f with non-existent path using parent refs
+ stdout = barebox.run_check('readlink -f ../../nonexistent')
+ assert stdout == ["/tmp/readlink-test4/a/nonexistent"]
+
+ # Test -e with parent references (existing path)
+ stdout = barebox.run_check('readlink -e ..')
+ assert stdout == ["/tmp/readlink-test4/a/b"]
+
+ # Test -e with parent references (non-existent final component)
+ _, _, returncode = barebox.run('readlink -e ../../nonexistent')
+ assert returncode != 0
+
+ # Cleanup
+ barebox.run_check('rm -r /tmp/readlink-test4')
+
+
+def test_cmd_readlink_edge_cases(barebox, barebox_config):
+ skip_disabled(barebox_config, "CONFIG_CMD_READLINK", "CONFIG_CMD_MKDIR")
+
+ # Create test directory structure
+ barebox.run_check('mkdir -p /tmp/readlink-test5/dir')
+ barebox.run_check('cd /tmp/readlink-test5')
+
+ # Test with trailing slash on existing directory
+ stdout = barebox.run_check('readlink -f dir/')
+ assert stdout == ["/tmp/readlink-test5/dir"]
+
+ # Test with multiple slashes
+ stdout = barebox.run_check('readlink -f ./dir//subpath')
+ assert stdout == ["/tmp/readlink-test5/dir/subpath"]
+
+ # Test self-reference
+ stdout = barebox.run_check('readlink -f ./././dir')
+ assert stdout == ["/tmp/readlink-test5/dir"]
+
+ # Test -e with trailing slash on existing directory
+ stdout = barebox.run_check('readlink -e dir/')
+ assert stdout == ["/tmp/readlink-test5/dir"]
+
+ # Test absolute path that's already canonical
+ stdout = barebox.run_check('readlink -f /tmp/readlink-test5/dir')
+ assert stdout == ["/tmp/readlink-test5/dir"]
+
+ stdout = barebox.run_check('readlink -e /tmp/readlink-test5/dir')
+ assert stdout == ["/tmp/readlink-test5/dir"]
+
+ # Cleanup
+ barebox.run_check('rm -r /tmp/readlink-test5')
--
2.47.3
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2026-01-26 10:52 [PATCH] commands: readlink: restore support for non-existent last component Ahmad Fatoum
2026-01-27 7:46 ` Sascha Hauer
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