Add command to get/set sysfs files

By using a command (instead of echo), it is possible to set capability
and avoid sudo.

1 files changed, 79 insertions, 0 deletions

diff --git a/src/sysfs.c b/src/sysfs.c
new file mode 100644
index 0000000..a84cea4
--- /dev/null
+++ b/src/sysfs.c
@@ -0,0 +1,79 @@
+/*
+ * Program to set sysfs value - similar to sysctl commmand
+ */
+
+#include <stdio.h>
+#include <limits.h>
+#include <stdlib.h>
+#include <errno.h>
+#include <string.h>
+
+#define SYS "/sys"
+
+static void get(const char *name)
+{
+	char path[PATH_MAX];
+	char buf[BUFSIZ];
+	FILE *f;
+
+	snprintf(path, PATH_MAX, SYS "/%s", name);
+	f = fopen(path, "r");
+	if (f == NULL) {
+		fprintf(stderr, "%s : %s\n", path, strerror(errno));
+		exit(1);
+	}
+
+	while (fgets(buf, BUFSIZ, f) != NULL)
+		fputs(buf, stdout);
+
+	if (ferror(f)) {
+		fprintf(stderr, "%s : read %s\n", path, strerror(errno));
+		exit(1);
+	}
+	fclose(f);
+}
+
+static void set(const char *name, const char *val)
+{
+	FILE *f;
+	char path[PATH_MAX];
+
+	snprintf(path, PATH_MAX, SYS "/%s", name);
+	f = fopen(path, "w");
+	if (f == NULL) {
+		fprintf(stderr, "%s : %s\n", path, strerror(errno));
+		exit(1);
+	}
+
+	fprintf(f, "%s\n", val);
+	fflush(f);
+
+	if (ferror(f)) {
+		fprintf(stderr, "%s : read %s\n", path, strerror(errno));
+		exit(1);
+	}
+	fclose(f);
+}
+
+int main(int argc, char **argv)
+{
+	if (argc == 1) {
+		fprintf(stderr, "Usage: %s variable\n", argv[0]);
+		fprintf(stderr, "       %s variable=value\n", argv[0]);
+		return 1;
+	}
+
+	while (--argc) {
+		char *ep, *arg = *++argv;
+
+		ep = strchr(arg, '=');
+		if (!ep)
+			get(arg);
+		else {
+			*ep++ = '\0';
+			set(arg, ep);
+		}
+	}
+
+	return 0;
+}