getfattr: new applet

function                                             old     new   delta
getfattr_main                                          -     309    +309
print_attr                                             -     115    +115
packed_usage                                       34576   34631     +55
.rodata                                           105349  105395     +46
lgetxattr                                              -      41     +41
getxattr                                               -      41     +41
llistxattr                                             -      35     +35
listxattr                                              -      35     +35
applet_names                                        2806    2815      +9
applet_main                                         1620    1624      +4
------------------------------------------------------------------------------
(add/remove: 7/0 grow/shrink: 4/0 up/down: 690/0)             Total: 690 bytes

Signed-off-by: YU Jincheng <shana@zju.edu.cn>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 131 insertions, 0 deletions

diff --git a/miscutils/getfattr.c b/miscutils/getfattr.c
new file mode 100644
index 0000000..59b6f6b
--- /dev/null
+++ b/miscutils/getfattr.c
@@ -0,0 +1,131 @@
+/*
+ * getfattr - get extended attributes of filesystem objects.
+ *
+ * Copyright (C) 2023 by LoveSy <lovesykun@gmail.com>
+ *
+ * Licensed under GPLv2, see file LICENSE in this source tree.
+ */
+//config:config GETFATTR
+//config:	bool "getfattr (12.3 kb)"
+//config:	default y
+//config:	help
+//config:	Get extended attributes on files
+
+//applet:IF_GETFATTR(APPLET_NOEXEC(getfattr, getfattr, BB_DIR_USR_BIN, BB_SUID_DROP, getfattr))
+
+//kbuild:lib-$(CONFIG_GETFATTR) += getfattr.o
+
+#include <stdio.h>
+#include <sys/xattr.h>
+#include "libbb.h"
+
+//usage:#define getfattr_trivial_usage
+//usage:       "[-h] {-d|-n ATTR} FILE...\n"
+//usage:#define getfattr_full_usage "\n\n"
+//usage:       "Get extended attributes"
+//usage:     "\n"
+//usage:     "\n	-h		Do not follow symlinks"
+//usage:     "\n	-d		Dump all attributes"
+//usage:     "\n	-n ATTR		Get attribute ATTR"
+
+enum {
+	OPT_h = (1 << 0),
+	OPT_d = (1 << 1),
+};
+
+static int print_attr(const char *file, const char *name, char **buf, size_t *bufsize)
+{
+	ssize_t len;
+
+	if (*bufsize == 0)
+		goto grow;
+ again:
+	len = ((option_mask32 &  OPT_h) ? lgetxattr: getxattr)(file, name, *buf, *bufsize);
+	if (len < 0) {
+		if (errno != ERANGE)
+			return len;
+ grow:
+		*bufsize = (*bufsize * 2) + 1024;
+		*buf = xrealloc(*buf, *bufsize);
+		goto again;
+	}
+	printf("%s=\"%.*s\"\n", name, len, *buf);
+	return 0;
+}
+
+static ssize_t list_attr(const char *file, char **list, size_t *listsize)
+{
+	ssize_t len;
+
+	if (*listsize == 0)
+		goto grow;
+ again:
+	len = ((option_mask32 &  OPT_h) ? llistxattr : listxattr)(file, *list, *listsize);
+	if (len < 0) {
+		if (errno != ERANGE)
+			return len;
+ grow:
+		*listsize = (*listsize * 2) + 1024;
+		*list = xrealloc(*list, *listsize);
+		goto again;
+	}
+	return len;
+}
+
+int getfattr_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
+int getfattr_main(int argc UNUSED_PARAM, char **argv)
+{
+	const char *name;
+	int status;
+	int opt;
+	char *buf = NULL;
+	size_t bufsize = 0;
+	char *list = NULL;
+	size_t listsize = 0;
+
+	opt = getopt32(argv, "^"
+		"hdn:"
+		/* Min one arg; exactly one of -n or -d is required. */
+		"\0" "-1:d:n:n--d:d--n"
+		, &name
+	);
+	argv += optind;
+	status = EXIT_SUCCESS;
+
+	do {
+		int r;
+		if (opt & OPT_d) {
+			ssize_t len = list_attr(*argv, &list, &listsize);
+			if (len > 0) {
+				char *key;
+				printf("# file: %s\n", *argv);
+				key = list;
+				while (len > 0) {
+					ssize_t keylen;
+					r = print_attr(*argv, key, &buf, &bufsize);
+					if (r)
+						goto err;
+					keylen = strlen(key) + 1;
+					key += keylen;
+					len -= keylen;
+				}
+				bb_putchar('\n');
+			}
+		} else {
+			printf("# file: %s\n", *argv);
+			r = print_attr(*argv, name, &buf, &bufsize);
+			if (r) {
+ err:
+				bb_simple_perror_msg(*argv);
+				status = EXIT_FAILURE;
+				// continue; maybe?
+			}
+			bb_putchar('\n');
+		}
+	} while (*++argv);
+
+	if (ENABLE_FEATURE_CLEAN_UP)
+		free(buf);
+
+	fflush_stdout_and_exit(status);
+}