Improve docs, provide a testcase.

* .gitignore: New file.
* Makefile: Update.
* ion.1: Rewrite.
* ion.c (getarg0): Bugfix.
* test/.gitignore: New file.
* test/Makefile: New file.
* test/a.c: New file.
* test/b.c: New file.

8 files changed, 213 insertions, 42 deletions

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..0976d46
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,6 @@
+.emacs*
+*.o
+*~
+core
+*.tar.*
+ion
diff --git a/Makefile b/Makefile
index 788d790..1c7d20e 100644
--- a/Makefile
+++ b/Makefile
@@ -1,2 +1,6 @@
 ion: ion.c
 	cc -ggdb -Wall -oion -DCANONICAL_NAME=\"ion\" ion.c
+check: 
+	make -C test check
+clean: 
+	rm -f ion *.o
diff --git a/ion.1 b/ion.1
index 926776e..a21f545 100644
--- a/ion.1
+++ b/ion.1
@@ -13,7 +13,7 @@
 .\"
 .\" You should have received a copy of the GNU General Public License
 .\" along with Ion.  If not, see <http://www.gnu.org/licenses/>.
-.TH ION 1 "March 4, 2013" "ION"
+.TH ION 1 "March 9, 2013" "ION"
 .SH NAME
 ion \- Input/Output Normalizer
 .SH SYNOPSIS
@@ -21,34 +21,64 @@ ion \- Input/Output Normalizer
 .I PROGRAM
 [\fIARGS\fR...]
 .SH DESCRIPTION
-Some interactive shell programs incorrectly bufferize their output,
-which can cause problems when another program is trying to communicate
-with them via pipes.  For example, GNU
-.BR ed (1)
-fails to flush its
+.B Ion
+runs the supplied program with its three standard streams connected to
+a
+.BR tty .
+Normally this means that the program's
+.BR stdin ,
+.BR stdout ,
+and
 .B stderr
-after issuing an error explanation message.  Another example is
-.BR xfs_db (8)
-from xfsprogs v. 3.1.7, which does not flush
-.B stdout
-after outputting its prompt.  The list can be continued.
+will be line-buffered.
 .PP
-.B Ion
-attempts to fix it by invoking the program supplied as its argument
-and attaching a
-.B PTY
-to its three basic streams.  It then acts as a proxy between the
-program and the process that invoked it, transparently sending back
-and forth data through these streams.
+Admittedly, there's not much sense in that when started from the
+command line.  However, there is a scenario when the use of
+.B ian
+becomes necessary.  It is when an interactive
+.B PROGRAM
+is invoked from another program, which communicates with it via pipes.
+Unless the invoked
+.I PROGRAM
+takes special precautions, its standard streams would become fully
+buffered, which would make any interactive use meaningless.  In this
+scenario, the calling program is supposed to run 
+.B ion
+with its command line being the
+.I PROGRAM
+name and its arguments.  When invoked so, the calling program would be
+able to communicate with the
+.I PROGRAM
+just as a human being would using the console.
 .PP
-Unless invoked as
+One example of such usage is
+.BR xfs_db (8),
+which, when called from an interactive program such as
+.BR xfs_irecover (8)
+from Jan Engelhardt's
+.B hxtools
+fails to communicate because it uses full buffering by default.
+.PP 
+Often it is not possible or desirable to alter the calling program so,
+that it would run
+.B ion
+instead of the intended
+.IR PROGRAM .
+Taking into account this,
 .B ion
-this program tries to spawn the program it is invoked as with the
-arguments from its command line.  This feature is particularly useful
-if your program invokes another not by its absolute pathname, but
-rather using the shell
-.B PATH
-instead.  To use this, make sure you link
+implements a special calling convention.  Namely, unless invoked as
+.B ion
+it tries to spawn the program it is invoked as with the arguments from
+its command line.  The
+.I PROGRAM
+(unless started with an absolute pathname) is then searched in the
+system
+.BR PATH ,
+excluding the directory where the invoked copy of
+.B ion
+itself is located.
+.PP
+To use this feature, make sure you link
 .B ion
 to a program name in a directory preceding the one where the actual
 program is located in
@@ -82,8 +112,7 @@ from your program will first invoke
 which will invoke
 .B xfs_db
 from
-.B /usr/bin
-and will let your program communicate with it.
+.BR /usr/bin .
 .SH AUTHORS
 Sergey Poznyakoff
 .SH "BUG REPORTS"
diff --git a/ion.c b/ion.c
index 45225f7..93f7428 100644
--- a/ion.c
+++ b/ion.c
@@ -114,7 +114,8 @@ getarg0(char **argv)
 	size_t bufsize = 0;
 	int found;
 	
-	if (argv[0][0] == '/') {
+	pn = strrchr(argv[0], '/');
+	if (pn) {
 		if (stat(argv[0], &st)) {
 			perror("stat");
 			return 1;
@@ -122,7 +123,6 @@ getarg0(char **argv)
 		dev = st.st_dev;
 		ino = st.st_ino;
 		
-		pn = strrchr(argv[0], '/');
 		*pn++ = 0;
 	} else {
 		pn = argv[0];
@@ -287,7 +287,7 @@ main(int argc, char **argv)
 		for (; i < sysconf(_SC_OPEN_MAX); i++)
 			close(i);
 		execvp(argv[0], argv);
-		perror("execvp");
+		perror(argv[0]);
 		_exit(EX_EXEC);
 	}
 
@@ -295,8 +295,8 @@ main(int argc, char **argv)
 	bufinit(obuf);
 	for (stop = 0; !stop;) {
 		FD_ZERO(&rdset);
-		FD_SET(in, &rdset);
-		FD_SET(master, &rdset);
+		if (in != -1) FD_SET(in, &rdset);
+		if (master != -1) FD_SET(master, &rdset);
 		
 		if (select(master + 1, &rdset, NULL, NULL, NULL) < 0) {
 			if (errno == EINTR) {
@@ -308,28 +308,22 @@ main(int argc, char **argv)
 			exit(EX_ERR);
 		}
 
-		if (in >= 0 && FD_ISSET(in, &rdset)) {
-			bufread(ibuf, in);
-		}
+		if (in >= 0 && FD_ISSET(in, &rdset)) bufread(ibuf, in);
 		
-		if (master >= 0 && FD_ISSET(master, &rdset)) {
+		if (master >= 0 && FD_ISSET(master, &rdset)) 
 			bufread(obuf, master);
-		}
 
 		if (out >= 1 && !bufisempty(obuf)) {
 			tr(&obuf);
 			bufwrite(obuf, out);
 		}
 
-		if (master > 0 && !bufisempty(ibuf)) {
-			bufwrite(ibuf, master);
-		}
+		if (master > 0 && !bufisempty(ibuf)) bufwrite(ibuf, master);
 
 		if (bufisempty(ibuf)) bufinit(ibuf);
 		if (bufisempty(obuf)) {
 			bufinit(obuf);
-			if (master < 0)
-				stop = 1;
+			if (master < 0) stop = 1;
 		}
 	}
 
diff --git a/test/.gitignore b/test/.gitignore
new file mode 100644
index 0000000..f47cb20
--- /dev/null
+++ b/test/.gitignore
@@ -0,0 +1 @@
+*.out
diff --git a/test/Makefile b/test/Makefile
new file mode 100644
index 0000000..18a8143
--- /dev/null
+++ b/test/Makefile
@@ -0,0 +1,14 @@
+check: ../ion a.out b.out
+	@if a.out ../ion b.out; then \
+		echo "Success"; \
+	else \
+		echo >&2 "FAILURE"; \
+		false; \
+	fi
+
+.c.out:
+	cc -o$@ $<
+
+
+
+
diff --git a/test/a.c b/test/a.c
new file mode 100644
index 0000000..b1f715b
--- /dev/null
+++ b/test/a.c
@@ -0,0 +1,98 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <assert.h>
+#include <string.h>
+
+char prompt[] = "rev> ";
+int promptlen = sizeof(prompt) - 1;
+char *input[] = { "adam", "word", "revert", NULL };
+char *output[] = { "mada", "drow", "trever", NULL };
+
+int
+main(int argc, char **argv)
+{
+	int ip[2], op[2];
+	pid_t pid;
+	int i;
+	FILE *ifile, *ofile;
+	char buf[128];
+	
+	assert(argc > 1);
+	argc--;
+	argv++;
+	assert(pipe(ip) == 0);
+	assert(pipe(op) == 0);
+
+	pid = fork();
+	assert(pid != -1);
+
+	if (pid == 0) {
+		/* ip[0] - child stdin
+		   ip[1] - master write
+		   op[0] - master read
+		   op[1] - child stdout
+		*/
+		close(ip[1]);
+		close(op[0]);
+		if (ip[0] != 0) {
+			close(0);
+			dup(ip[0]);
+			close(ip[0]);
+		}
+		if (op[1] != 1) {
+			close(1);
+			dup(op[1]);
+			close(op[1]);
+		}
+		execvp(argv[0], argv);
+		perror(argv[0]);
+		_exit(127);
+	}
+	/* master */
+	close(ip[0]);
+	close(op[1]);
+	ifile = fdopen(op[0], "r");
+	if (!ifile) {
+		perror("op[0]");
+		abort();
+	}
+	setlinebuf(ifile);
+	ofile = fdopen(ip[1], "w");
+	if (!ofile) {
+		perror("ip[1]");
+		abort();
+	}
+	setlinebuf(ofile);
+	for (i = 0; input[i]; i++) {
+		alarm(5);
+		if (fread(buf, promptlen, 1, ifile) != 1) {
+			fprintf(stderr, "%d: read error\n", __LINE__);
+			abort();
+		}
+		alarm(0);
+
+		if (strncmp(buf, prompt, promptlen)) {
+			fprintf(stderr, "%d: expected prompt, but got \"%*.*s\"\n",
+				__LINE__, promptlen, promptlen, buf);
+			abort();
+		}
+
+		fprintf(ofile, "%s\n", input[i]);
+
+		alarm(5);
+		if (!fgets(buf, sizeof(buf), ifile)) {
+			fprintf(stderr, "%d: read error\n", __LINE__);
+			abort();
+		}
+		alarm(0);
+		buf[strlen(buf)-1] = 0;
+		if (strcmp(buf, output[i])) {
+			fprintf(stderr, "%d: expected \"%s\", but got \"%s\"\n",
+				__LINE__, output[i], buf);
+			abort();
+		}
+	}
+	return 0;
+}
+		
diff --git a/test/b.c b/test/b.c
new file mode 100644
index 0000000..115d521
--- /dev/null
+++ b/test/b.c
@@ -0,0 +1,25 @@
+#include <stdio.h>
+
+int
+main()
+{
+	int i, j;
+	char buf[128];
+	static char prompt[] = "rev> ";
+
+	while (1) {
+		fwrite(prompt, strlen(prompt), 1, stdout);
+		if (!fgets(buf, sizeof(buf), stdin))
+			break;
+		j = strlen(buf) - 1;
+		if (buf[j] == '\n')
+			buf[j--] = 0;
+		for (i = 0; i < j; i++, j--) {
+			int c = buf[j];
+			buf[j] = buf[i];
+			buf[i] = c;
+		}
+		fprintf(stdout, "%s\n", buf);
+	}
+	return 0;
+}