util: Add fopen_fmt helper

Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>

include/util.h

@@ -162,6 +162,7 @@ extern void hex_dump(void *addr, unsigned long len);
 
 extern DIR *opendir_proc(char *fmt, ...);
 extern FILE *fopen_proc(char *fmt, char *mode, ...);
+extern FILE *fopen_fmt(char *fmt, char *mode, ...);
 extern int open_fmt(char *fmt, int mode, ...);
 
 #define __xalloc(op, size, ...)						\

util.c

@@ -352,6 +352,22 @@ FILE *fopen_proc(char *fmt, char *mode, ...)
 	return file;
 }
 
+FILE *fopen_fmt(char *fmt, char *mode, ...)
+{
+	FILE *file;
+	char fname[128];
+	va_list args;
+
+	va_start(args, mode);
+	vsnprintf(fname, sizeof(fname), fmt, args);
+	va_end(args);
+
+	file = fopen(fname, mode);
+	if (!file)
+		pr_perror("Can't open %s\n", fname);
+	return file;
+}
+
 int open_fmt(char *fmt, int mode, ...)
 {
 	int fd;