Add erasef(), formatted version of erase()

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

README.md

@@ -94,6 +94,10 @@ Helper Macros
 
   Erase file/directory with `remove()`.  Errors on `stderr`
 
+- `erasef(fmt, ...)`
+
+  Like `erase()` but takes a formatted printf-like string as argument.
+
 - `makedir(path)`
 
   Create directory, like `mkdir()`.  Errors on `stderr`

src/Makefile.am

@@ -4,8 +4,8 @@ libite_la_CPPFLAGS    = -D_GNU_SOURCE
 libite_la_CFLAGS      = -W -Wall -Wextra
 libite_la_LDFLAGS     = $(AM_LDFLAGS) -version-info 7:0:2
 libite_la_SOURCES     = chomp.c		copyfile.c			\
-			conio.c		conio.h				\
-			dir.c		fopenf.c	fremove.c	\
+			conio.c		conio.h		dir.c		\
+			erasef.c	fopenf.c	fremove.c	\
 			fexist.c	fisdir.c			\
 			fparseln.c	fsendfile.c			\
 			ifconfig.c	lfile.c				\

src/erasef.c

@@ -0,0 +1,66 @@
+/* Formatted erase()
+ *
+ * Copyright (c) 2021  Joachim Wiberg <troglobit@gmail.com>
+ *
+ * Permission to use, copy, modify, and/or distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#include <errno.h>
+#include <stdio.h>
+#include <stdarg.h>
+#include <stdlib.h>
+#include <unistd.h>
+
+#include "lite.h"
+
+/**
+ * erasef - Like erase() but with formatted string support
+ * @fmt:  Formatted string to be composed into a pathname
+ *
+ * This is a wrapper for the erase() function in lite.h, lessening the
+ * burden of having to compose the filename from parts in a seprate
+ * buffer.
+ *
+ * Returns:
+ * Upon successful completion erasef() returns POSIX OK(0), otherwise,
+ * -1 is returned and errno is set to indicate the error.
+ */
+int erasef(const char *fmt, ...)
+{
+	va_list ap;
+	char *file;
+	int len;
+
+	va_start(ap, fmt);
+	len = vsnprintf(NULL, 0, fmt, ap);
+	va_end(ap);
+
+	file = alloca(len + 1);
+	if (!file) {
+		errno = ENOMEM;
+		return -1;
+	}
+
+	va_start(ap, fmt);
+	vsnprintf(file, len + 1, fmt, ap);
+	va_end(ap);
+
+	return erase(file);
+}
+
+/**
+ * Local Variables:
+ *  indent-tabs-mode: t
+ *  c-file-style: "linux"
+ * End:
+ */

src/lite.h

@@ -60,6 +60,9 @@ typedef struct lfile lfile_t;
 typedef struct sdbuf sdbuf_t;
 
 char   *chomp      (char *str);
+
+int     erasef     (const char *fmt, ...);
+	
 char   *fparseln   (FILE *, size_t *, size_t *, const char[3], int);
 
 int     fexist     (const char *file);

tests/touch.c

@@ -1,3 +1,4 @@
+/* test of touch(), touchf(), erase(), and erasef() */
 #include <err.h>
 #include <paths.h>
 #include <signal.h>
@@ -53,7 +54,15 @@ static int formatted(char *file)
 		errx(1, "touchf() does not detect failure to create file " FMT, file);
 
 	PRINT("File " FMT " really does exist!\n", file);
-	erase(vrfy);
+
+	erasef(FMT, file);
+	if (fexist(vrfy)) {
+		int saved = errno;
+
+		erase(vrfy);
+		errno = saved;
+		errx(1, "erasef() failed removing the created file " FMT, file);
+	}
 
 	return 0;
 }