ChangeLog, Makefile.in, e2label.c:

  e2label.c: New file contributed by Andries Brouwer which provides an
  easy-to-use interface to modify the filesystem label.

1 files changed, 92 insertions, 0 deletions

diff --git a/misc/e2label.c b/misc/e2label.c
new file mode 100644
index 00000000..2b4f1711
--- /dev/null
+++ b/misc/e2label.c
@@ -0,0 +1,92 @@
+/*
+ * e2label.c		- Print or change the volume label on an ext2 fs
+ *
+ * aeb, 970714
+ *
+ */
+
+#include <fcntl.h>
+#include <stdio.h>
+
+#define EXT2_SUPER_MAGIC 0xEF53
+
+#define VOLNAMSZ 16
+
+struct ext2_super_block {
+	char  s_dummy0[56];
+	unsigned char  s_magic[2];
+	char  s_dummy1[62];
+	char  s_volume_name[VOLNAMSZ];
+	char  s_last_mounted[64];
+	char  s_dummy2[824];
+} sb;
+
+int
+open_e2fs (char *dev, int mode) {
+	int fd;
+
+	fd = open(dev, mode);
+	if (fd < 0) {
+	     perror(dev);
+	     fprintf (stderr, "e2label: cannot open %s\n", dev);
+	     exit(1);
+	}
+	if (lseek(fd, 1024, SEEK_SET) != 1024) {
+	     perror(dev);
+	     fprintf (stderr, "e2label: cannot seek to superblock\n");
+	     exit(1);
+	}
+	if (read(fd, (char *) &sb, sizeof(sb)) != sizeof(sb)) {
+	     perror(dev);
+	     fprintf (stderr, "e2label: error reading superblock\n");
+	     exit(1);
+	}
+	if (sb.s_magic[0] + 256*sb.s_magic[1] != EXT2_SUPER_MAGIC) {
+	     fprintf (stderr, "e2label: not an ext2 filesystem\n");
+	     exit(1);
+	}
+
+	return fd;
+}
+
+void
+print_label (char *dev) {
+	char label[VOLNAMSZ+1];
+
+	open_e2fs (dev, O_RDONLY);
+	label[VOLNAMSZ] = 0;
+	strncpy(label, sb.s_volume_name, VOLNAMSZ);
+	printf("%s\n", label);
+}
+
+void
+change_label (char *dev, char *label) {
+	int fd;
+
+	fd = open_e2fs(dev, O_RDWR);
+	memset(sb.s_volume_name, 0, VOLNAMSZ);
+	strncpy(sb.s_volume_name, label, VOLNAMSZ);
+	if (lseek(fd, 1024, SEEK_SET) != 1024) {
+	     perror(dev);
+	     fprintf (stderr, "e2label: cannot seek to superblock again\n");
+	     exit(1);
+	}
+	if (write(fd, (char *) &sb, sizeof(sb)) != sizeof(sb)) {
+	     perror(dev);
+	     fprintf (stderr, "e2label: error writing superblock\n");
+	     exit(1);
+	}
+}
+
+int
+main (int argc, char ** argv) {
+	if (argc == 2)
+	     print_label(argv[1]);
+	else if (argc == 3)
+	     change_label(argv[1], argv[2]);
+	else {
+	     fprintf(stderr, "Usage: e2label device [newlabel]\n");
+	     exit(1);
+	}
+	return 0;
+}