add ipc pipe (#28)

user/apps/shell/Makefile

@@ -1,4 +1,4 @@
-all: shell.o cmd.o cmd_help.o
+all: shell.o cmd.o cmd_help.o cmd_test.o
 
 	ld -b elf64-x86-64 -z muldefs -o $(tmp_output_dir)/shell  $(shell find . -name "*.o") $(shell find $(sys_libs_dir) -name "*.o") -T shell.lds
 
@@ -9,5 +9,8 @@ shell.o: shell.c
 cmd.o: cmd.c
 	gcc $(CFLAGS) -c cmd.c  -o cmd.o
 
+cmd_test.o: cmd_test.c
+	gcc $(CFLAGS) -c cmd_test.c  -o cmd_test.o
+
 cmd_help.o: cmd_help.c
 	gcc $(CFLAGS) -c cmd_help.c  -o cmd_help.o

user/apps/shell/cmd.c

@@ -12,6 +12,7 @@
 #include <libc/sys/wait.h>
 #include <libc/sys/stat.h>
 #include "cmd_help.h"
+#include "cmd_test.h"
 
 // 当前工作目录（在main_loop中初始化）
 char *shell_current_path = NULL;
@@ -34,6 +35,7 @@ struct built_in_cmd_t shell_cmds[] =
         {"about", shell_cmd_about},
         {"free", shell_cmd_free},
         {"help", shell_help},
+        {"pipe", shell_pipe_test},
 
 };
 // 总共的内建命令数量

user/apps/shell/cmd_test.c

@@ -0,0 +1,32 @@
+#include "cmd_test.h"
+#include <libc/stdio.h>
+#include <libc/stdlib.h>
+#include <libc/string.h>
+#include <libc/unistd.h>
+
+int shell_pipe_test(int argc, char **argv)
+{
+    int ret = -1;
+    int fd[2];
+    pid_t pid;
+    char buf[512] = {0};
+    char *msg = "hello world";
+
+    ret = pipe(fd);
+    if (-1 == ret) {
+        printf("failed to create pipe\n");
+        return -1;
+    }
+    pid = fork();
+    if (0 == pid) { 
+        // close(fd[0]);
+        ret = write(fd[1], msg, strlen(msg)); 
+        exit(0);
+    } else {          
+        // close(fd[1]);
+        ret = read(fd[0], buf, sizeof(buf));
+        printf("parent read %d bytes data: %s\n", ret, buf);
+    }
+
+    return 0;
+}

user/apps/shell/cmd_test.h

@@ -0,0 +1,4 @@
+#pragma once
+
+#include "cmd.h"
+int shell_pipe_test(int argc, char **argv);