Add support for systemf(), formatted system() replacement

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

README.md

@@ -304,6 +304,12 @@ Generic Functions
   Find matching string in an array of strings.  Returns index in array
   on match, or `-1` on error or not found.
 
+`systemf(fmt, ...)`
+
+  Like `system()`, but takes a formatted string as argument.  This
+  greatly simplifies operations that usually consist of composing a
+  command from parts into a dynamic buffer before calling it.
+
 - `telnet_open(), telnet_close(), telnet_expect()`
 
   Poor mans telnet expect in C.  Opens connection to a Telnet service;

src/Makefile.am

@@ -14,7 +14,8 @@ 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	telnet.c	tempfile.c	\
+			strmatch.c	systemf.c			\
+			telnet.c	tempfile.c			\
 			yorn.c		which.c				\
 			lite.h		strlite.h			\
 			queue.h		tree.h

src/lite.h

@@ -98,6 +98,8 @@ void   *reallocarray(void *optr, size_t nmemb, size_t size);
 void    progress       (int percent, int max_width);
 void    progress_simple(int percent);
 
+int     systemf        (const char *fmt, ...);
+
 sdbuf_t*telnet_open    (int addr, short port);
 int     telnet_close   (sdbuf_t *ctx);
 int     telnet_expect  (sdbuf_t *ctx, char *script[], FILE *output);

src/systemf.c

@@ -0,0 +1,73 @@
+/* Formatted system() which returns actual return status of command
+ *
+ * Copyright (c) 2020  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 <errno.h>
+#include <stdarg.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/wait.h>
+
+int systemf(const char *fmt, ...)
+{
+	va_list ap;
+	char *cmd;
+	int len, status;
+	int rc = -1;
+
+	va_start(ap, fmt);
+	len = vsnprintf(NULL, 0, fmt, ap);
+	va_end(ap);
+
+	va_start(ap, fmt);
+	cmd = alloca(++len);
+	if (!cmd) {
+		va_end(ap);
+		errno = ENOMEM;
+		return -1;
+	}
+
+	vsnprintf(cmd, len, fmt, ap);
+	va_end(ap);
+
+	status = system(cmd);
+
+	rc = WEXITSTATUS(status);
+	if (!WIFEXITED(status)) {
+		if (WIFSIGNALED(status) &&
+		    (WTERMSIG(status) == SIGINT ||
+		     WTERMSIG(status) == SIGQUIT)) {
+			errno = EINTR;
+			rc = -1;
+		} else if (!rc) {
+			/*
+			 * Alert callee that command didn't complete
+			 * successfully.  Some programs don't change
+			 * their exit code when signaled.
+			 */
+			rc = 1;
+		}
+	}
+
+	return rc;
+}
+
+/**
+ * Local Variables:
+ *  indent-tabs-mode: t
+ *  c-file-style: "linux"
+ * End:
+ */

tests/.gitignore

@@ -17,6 +17,7 @@ progress
 rsync
 str
 strmatch
+systemf
 tempfile
 touch
 tree

tests/Makefile.am

@@ -17,6 +17,7 @@ TESTS          += progress
 TESTS          += rsync
 TESTS          += str
 TESTS          += strmatch
+TESTS          += systemf
 TESTS          += touch
 TESTS          += tempfile
 TESTS          += which

tests/systemf.c

@@ -0,0 +1,31 @@
+#include <err.h>
+#include "check.h"
+
+int main(void)
+{
+	struct { char *cmd; int rc; } list[] = {
+		{ "false",          1 },
+		{ "true",           0 },
+		{ "kill -9 $$",     1 },
+		{ "kill -QUIT $$", -1 },
+		{ "kill -INT $$",  -1 }
+	};
+
+	for (size_t i = 0; i < NELEMS(list); i++) {
+		int rc;
+
+		rc = systemf("%s", list[i].cmd);
+		if (rc != list[i].rc)
+			err(rc, "Failed command %s", list[i].cmd);
+	}
+
+	return 0;
+}
+
+/**
+ * Local Variables:
+ *  indent-tabs-mode: t
+ *  c-file-style: "linux"
+ * End:
+ */
+