2 files changed, 69 insertions, 0 deletions
diff --git a/shell/beispiele/dup/Makefile b/shell/beispiele/dup/Makefile
new file mode 100644
index 0000000..0f73ac4
--- /dev/null
+++ b/shell/beispiele/dup/Makefile
@@ -0,0 +1,18 @@
+#!/usr/bin/make
+.SUFFIXES:
+
+CFLAGS = -c -Os -Wall -Werror
+
+%.o: %.c
+	$(CC) $(CFLAGS) $^ -o $@
+
+%: %.o
+	$(CC) -o $@ $^
+
+all: dup
+
+run: all
+	./dup
+
+clean:
+	$(RM) $(RMFILES) dup
diff --git a/shell/beispiele/dup/dup.c b/shell/beispiele/dup/dup.c
new file mode 100644
index 0000000..ea3c5a6
--- /dev/null
+++ b/shell/beispiele/dup/dup.c
@@ -0,0 +1,51 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+
+/* https://www.youtube.com/watch?v=gaXigSu72A4 */
+static inline void die(const char* msg) {
+	perror(msg);
+	exit(EXIT_FAILURE);
+}
+
+int main(int argc, char **argv) {
+	int pdes[2];
+	pid_t child;
+ 	
+	if (pipe(pdes) < 0)
+		die("pipe()");
+ 	
+	if ((child = fork()) < 0)
+		die("fork()");
+ 	
+	if (child == 0) {
+		/* child process */
+      	close(pdes[0]);
+		close(1);       /* close stdout */
+		
+		if (dup(pdes[1]) < 0)
+			die("dup()");
+		
+		/* now stdout and pdes[1] are equivalent (dup returns lowest free descriptor) */
+		if (execlp("cat", "cat", "/etc/passwd", NULL) < 0)
+			die("execlp()");
+		
+		exit(EXIT_SUCCESS);
+	}
+	else {
+		/* parent process */
+		close(0);       /* close stdin */
+		close(pdes[1]);
+		
+		if (dup(pdes[0]) < 0)
+			die("dup()");
+		
+		/* now stdin and pdes[0] are equivalent (dup returns lowest free descriptor) */
+		if (execlp("wc", "wc", "-l", NULL) < 0)
+			die("execlp()");
+		
+		exit(EXIT_SUCCESS);
+	}
+	
+	return 0;
+}