start work on pspipe(1) again

pscat/Makefile

@@ -1,13 +1,18 @@
+all: pscat
+
 pscat: pscat.o ../libpsargs/libpsargs.o
 	$(CC) $(CFLAGS) -g -o pscat ../libpsargs/libpsargs.o pscat.o
 
 pscat.o: pscat.c
-	$(CC) $(CFLAGS) -c -I../libpsargs -o pscat.o pscat.c
+	$(CC) $(CFLAGS) -c -DPSCAT=1 -I../libpsargs -o pscat.o pscat.c
+
+pspipe: pspipe.o ../libpsargs/libpsargs.o
+	$(CC) $(CFLAGS) -g -o pspipe ../libpsargs/libpsargs.o pspipe.o
+
+pspipe.o: pscat.c
+	$(CC) $(CFLAGS) -c -DPSPIPE=1 -I../libpsargs -o pspipe.o pscat.c
 
 ../libpsargs/libpsargs.o:
 	$(MAKE) -C ../libpsargs
 
-clean:
-	rm -f *.o pscat
-
-.PHONY: clean
+.PHONY: all

pscat/pscat.c

@@ -1,43 +1,94 @@
+#include <errno.h> /* errno */
 #include <stdio.h> /* fprintf(3), stderr */
+#include <string.h> /* strerror(3) */
 #include <sysexits.h> /* EX_USAGE */
 #include <unistd.h> /* execvp(3) */
 #include <sys/types.h> /* <sys/wait.h> */
 #include <sys/wait.h> /* wait(2) */
 
-#include "libpsargs.h"
-
-static char *program_name = "pscat";
+#include "libpsargs.h" /* check_arg(3), corresponding_arg(3) */
 
 #define L_PAREN '['
 #define R_PAREN ']'
 
+#if defined(PSCAT)
+static char *program_name = "pscat";
+
 int
-forking(char **argv){
+f(char **argv){
 	int child;
 	char **corr;
 
-	corr = corresponding_arg(argv, L_PAREN, R_PAREN);
-	*corr = NULL;
-	if(fork() == 0){
-		execvp(argv[1], argv+1);
-	}else{
+	*(corr = corresponding_arg(argv, L_PAREN, R_PAREN)) = NULL;
+	switch(fork()){
+	case -1:
+		fprintf(stderr, "%s: %s\n", program_name, strerror(errno));
+		return EX_OSERR;
+	case 0: execvp(argv[1], argv+1);
+	default:
 		wait(&child);
 		argv = corr;
-		if(*++argv == NULL)
-			return WIFEXITED(child) * WEXITSTATUS(child);
-		else
-			return forking(argv);
+		return *++argv == NULL
+			? WIFEXITED(child) * WEXITSTATUS(child)
+			: f(argv);
 	}
 }
 
+#elif defined(PSPIPE)
+static char *program_name = "pspipe";
+
+/* At the start of the loop argv[0] is { '[', '\0' } and file descriptor 0 is
+ * the intended standard input */
+int
+f(char **argv){
+	int child;
+	char **corr;
+	static int fd[2];
+	int r;
+
+	*(corr = corresponding_arg(argv, L_PAREN, R_PAREN)) = NULL;
+	if(corr[1] != NULL){
+		if(pipe(fd) != 0){
+			fprintf(stderr,
+				"%s: %s: %s\n",
+				program_name, argv[1], strerror(errno)
+			);
+			return EX_OSERR;
+		}
+	}
+	if((r = fork()) == -1){
+		printf(stderr, "%s: %s\n", program_name, strerror(errno));
+		return EX_OSERR;
+	}
+	if(r == 0)
+		dup2(fd[0], 0);
+	else
+		dup2(fd[1], 1);
+
+	close(fd[1]);
+	close(fd[0]);
+
+	if(r == 1)
+		execvp(argv[1], argv+1);
+	else{
+		argv = corr;
+		return *++argv == NULL
+			? WIFEXITED(child) * WEXITSTATUS(child)
+			: f(argv);
+	}
+}
+
+#endif
+
 int main(int argc, char *argv[]){
 
+	if(argc != 0)
+		program_name = argv[0];
 	if(check_arg(++argv, L_PAREN, R_PAREN) == 0){
 		fprintf(stderr,
 			"Usage: %s \"[\" [utility [argument...]] \"]\" ...\n",
-			argv[-1] == NULL ? program_name : argv[-1]
+			program_name
 		);
 		return EX_USAGE;
-	}else
-		return forking(argv);
+	}else	return f(argv);
 }