New helper function: echo(), like shell echo but for C

Signed-off-by: Joachim Nilsson <troglobit@gmail.com>

src/util.c

@@ -25,6 +25,7 @@
 #include <ctype.h>		/* isprint() */
 #include <errno.h>
 #include <string.h>
+#include <stdarg.h>
 #include <stdlib.h>
 #include <unistd.h>
 #include <sys/sysinfo.h>	/* sysinfo() */
@@ -46,6 +47,32 @@ char *progname(char *arg0)
        return prognm;
 }
 
+int echo(char *file, int append, char *fmt, ...)
+{
+	va_list ap;
+	FILE *fp;
+
+	if (!file)
+		fp = stdout;
+	else
+		fp = fopen(file, append ? "a" : "w");
+	if (!fp)
+		return -1;
+
+	if (fmt) {
+		va_start(ap, fmt);
+		vfprintf(fp, fmt, ap);
+		va_end(ap);
+	}
+
+	/* echo(1) always adds a newline */
+	fprintf(fp, "\n");
+	if (file)
+		fclose(fp);
+
+	return 0;
+}
+
 int strtobytes(char *arg)
 {
 	int mod = 0, bytes;

src/util.h

@@ -39,6 +39,7 @@ extern char *prognm;
 #include <lite/conio.h>
 
 char *progname     (char *arg0);
+int   echo         (char *file, int append, char *fmt, ...);
 int   strtobytes   (char *arg);
 void  do_sleep     (unsigned int sec);