@@ -33,6 +33,9 @@ int tracefs_instance_file_write(struct tracefs_instance *instance,
char *tracefs_instance_file_read(struct tracefs_instance *instance,
char *file, int *psize);
+bool tracefs_file_exist(struct tracefs_instance *instance, char *name);
+bool tracefs_dir_exist(struct tracefs_instance *instance, char *name);
+
/* events */
void tracefs_list_free(char **list);
char **tracefs_event_systems(const char *tracing_dir);
@@ -13,7 +13,7 @@
#include <errno.h>
#include <sys/stat.h>
#include <fcntl.h>
-
+#include <linux/limits.h>
#include "tracefs.h"
#include "tracefs-local.h"
@@ -247,3 +247,47 @@ char *tracefs_instance_file_read(struct tracefs_instance *instance,
return buf;
}
+
+static bool check_file_exist(struct tracefs_instance *instance,
+ char *name, bool dir)
+{
+ char file[PATH_MAX];
+ struct stat st;
+ char *path;
+ int ret;
+
+ path = tracefs_instance_get_dir(instance);
+ snprintf(file, PATH_MAX, "%s/%s", path, name);
+ tracefs_put_tracing_file(path);
+ ret = stat(file, &st);
+ if (ret < 0)
+ return false;
+
+ return !dir == !S_ISDIR(st.st_mode);
+}
+
+/**
+ * tracefs_file_exist - Check if a file with given name exists in given instance
+ * @instance: ftrace instance, can be NULL for the top instance
+ * @name: name of the file
+ *
+ * Returns true if the file exists, false otherwise
+ *
+ * If a directory with the given name exists, false is returned.
+ */
+bool tracefs_file_exist(struct tracefs_instance *instance, char *name)
+{
+ return check_file_exist(instance, name, false);
+}
+
+/**
+ * tracefs_dir_exist - Check if a directory with given name exists in given instance
+ * @instance: ftrace instance, can be NULL for the top instance
+ * @name: name of the directory
+ *
+ * Returns true if the directory exists, false otherwise
+ */
+bool tracefs_dir_exist(struct tracefs_instance *instance, char *name)
+{
+ return check_file_exist(instance, name, true);
+}
Some ftrace files and directories are optional, depending on specific kernel configuration or version. It is a good practice to check if the file / directory exist, before trying to access it. There are a lot of places in trace-cmd implementation with such checks. The new libtracefs APIs can be used for this, they are ftarce instance aware: bool tracefs_file_exist(struct tracefs_instance *instance, char *name); bool tracefs_dir_exist(struct tracefs_instance *instance, char *name); Signed-off-by: Tzvetomir Stoyanov (VMware) <tz.stoyanov@gmail.com> --- include/tracefs/tracefs.h | 3 +++ lib/tracefs/tracefs-instance.c | 46 +++++++++++++++++++++++++++++++++- 2 files changed, 48 insertions(+), 1 deletion(-)