Add support for yorn(), safe yes-or-no prompt

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

README.md

@@ -308,6 +308,11 @@ Generic Functions
   **Note:** `which("/bin/ps aux")` will return `/bin/ps`, or `TRUE`,
   provided of course `/bin/ps` exists.
 
+- `yorn(fmt, ...)`
+
+  Pose a question to user, appended with `(y/N)?`, returns `TRUE` for
+  yes (both `y` and `Y` are handled) and `FALSE` for everything else.
+
 
 GNU Functions
 -------------

src/Makefile.am

@@ -14,7 +14,7 @@ libite_la_SOURCES     = chomp.c		copyfile.c			\
 			reallocarray.c	rsync.c				\
 			strlcpy.c 	strlcat.c 	strtonum.c	\
 			strdupa.h	strndupa.h	strnlen.h	\
-			strmatch.c					\
+			strmatch.c	yorn.c				\
 			tempfile.c	which.c				\
 			lite.h		strlite.h			\
 			queue.h		tree.h
@@ -22,4 +22,5 @@ libite_la_SOURCES     = chomp.c		copyfile.c			\
 
 ## Distribute these header files in the <lite/...> name space
 pkgincludedir       = $(includedir)/lite
-pkginclude_HEADERS  = lite.h queue.h conio.h tree.h strlite.h strdupa.h strndupa.h strnlen.h
+pkginclude_HEADERS  = lite.h queue.h conio.h tree.h strlite.h strdupa.h	\
+		      strndupa.h strnlen.h

src/lite.h

@@ -95,6 +95,8 @@ void   *reallocarray(void *optr, size_t nmemb, size_t size);
 void    progress       (int percent, int max_width);
 void    progress_simple(int percent);
 
+int     yorn       (const char *fmt, ...);
+
 char   *which      (const char *cmd);
 int     whichp     (const char *cmd);
 

src/yorn.c

@@ -0,0 +1,92 @@
+/* Safe yes-or-no with prompt
+ *
+ * Copyright (c) 2009  Joachim Nilsson <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 <stdio.h>
+#include <stdio_ext.h>		/* __fpurge() */
+#include <stdarg.h>
+#include <termios.h>
+#include <unistd.h>
+
+static char rawgetch(void)
+{
+	struct termios savemodes, modmodes;
+	char val;
+
+	if (!isatty(STDIN_FILENO))
+		return getchar();
+
+	/* Backup terminal settings. */
+	if (tcgetattr(STDIN_FILENO, &savemodes) < 0) {
+		return -1;
+	}
+
+	/* "stty cbreak -echo" */
+	modmodes = savemodes;
+	modmodes.c_lflag &= ~ICANON;
+	modmodes.c_lflag &= ~ECHO;
+	modmodes.c_cc[VMIN] = 1;
+	modmodes.c_cc[VTIME] = 0;
+
+	/* Set terminal in raw mode. */
+	if (tcsetattr(STDIN_FILENO, TCSANOW, &modmodes) < 0) {
+		tcsetattr(STDIN_FILENO, TCSANOW, &savemodes);
+		return -1;
+	}
+
+	val = getchar();
+
+	/* Restore terminal to previous state. */
+	tcsetattr(STDIN_FILENO, TCSANOW, &savemodes);
+
+	return val;
+}
+
+/**
+ * yorn - Pose a a Yes or No question and return answer
+ * @fmt: Standard printf() style argument(s).
+ *
+ * This function prints the given question on screen, waits for user
+ * input in the form of yes or no.
+ *
+ * Returns:
+ * True(1) or False(0).  True if the answer is yes.
+ */
+int yorn(const char *fmt, ...)
+{
+	va_list ap;
+	char yorn;
+
+	va_start(ap, fmt);
+	vfprintf(stderr, fmt, ap);
+	va_end(ap);
+
+	__fpurge(stdin);
+	yorn = rawgetch();
+	printf("%c\n", yorn);
+	fflush(stdout);
+	if (yorn != 'y' && yorn != 'Y')
+		return 0;
+
+	return 1;
+}
+
+/**
+ * Local Variables:
+ *  indent-tabs-mode: t
+ *  c-file-style: "linux"
+ * End:
+ */

tests/.gitignore

@@ -17,3 +17,4 @@ tempfile
 touch
 tree
 which
+yorn

tests/Makefile.am

@@ -18,6 +18,7 @@ TESTS          += strmatch
 TESTS          += touch
 TESTS          += tempfile
 TESTS          += which
+TESTS          += yorn
 
 check_PROGRAMS  = $(TESTS)
 

tests/yorn.c

@@ -0,0 +1,32 @@
+#include <stdio.h>
+#include <unistd.h>
+#include <sys/wait.h>
+
+#include "check.h"
+
+int main(int argc, char *argv[])
+{
+	int chan[2];
+	int status;
+
+	pipe(chan);
+
+	if (fork() > 0) {
+		dup2(chan[0], STDIN_FILENO);
+		if (yorn("Do you really wanna do this (y/N)? ")) {
+			printf("Affirmative!\n");
+			_exit(0);
+		}
+
+		printf("OK, aborting!\n");
+		_exit(1);
+	}
+
+	sleep(1);
+	if (write(chan[1], "Y", 1) != 1)
+		return 1;
+
+	wait(&status);
+
+	return WEXITSTATUS(status);
+}