1 files changed, 132 insertions, 97 deletions

diff --git a/bcsh.c b/bcsh.c
index 08f7ac7..656d608 100644
--- a/bcsh.c
+++ b/bcsh.c
@@ -6,7 +6,8 @@ char *username;
 char pwd[100];
 
 int main(int argc, char **argv) {
-    // 获取当前登陆的用户名、系统主机名、当前工作路径
+    // get the hostname, username and current working directory
+    // to show the prompt
     gethostname(hostname, sizeof(hostname));
     getcwd(pwd, sizeof(pwd));
     username = getpwuid(getuid())->pw_name;
@@ -18,13 +19,14 @@ int main(int argc, char **argv) {
 }
 
 void showPrompt() {
-    printf("\033[01;32m%s@%s\033[00m:\033[33m%s\033[00m$ ", username, hostname,
-           pwd);
-    // 强制刷新缓冲区
+    printf("\033[01;32m%s"
+           "\033[35m@%s\033[00m:"
+           "\033[33m%s\033[00m$ ",
+           username, hostname, pwd);
     fflush(stdout);
 }
 
-Command *newcmd() {
+Command *newCmd() {
     Command *cmd = (Command *)malloc(sizeof(Command));
     cmd->argc = 0;
     cmd->args = NULL;
@@ -39,134 +41,167 @@ Command *newcmd() {
     return cmd;
 }
 
-int runcmd(Command *cmd) {
+int runCmd(Command *cmd) {
     int status;
     if (cmd == NULL) {
         fprintf(stderr, "cmd is NULL\n");
         return -1;
     }
+    switch (cmd->type) {
+    case CMD_NORMAL:
+        status = runNormalCmd(cmd);
+        break;
+    case CMD_PIPE:
+        status = runPipeCmd(cmd);
+        break;
+    case CMD_AND:
+    case CMD_OR:
+        status = runAndOrCmd(cmd);
+        break;
+    }
 
-    if (cmd->type == CMD_NORMAL) {
-        pid_t pid;
-        if (!strcmp(cmd->args[0], "exit")) {
-            printf("Good Bye, %s!\n", username);
-            exit(0);
-        } else if (!strcmp(cmd->args[0], "cd")) {
-            if (cmd->argc == 1) {
-                chdir(getenv("HOME"));
-            } else {
-                chdir(cmd->args[1]);
-            }
-            printf("\r");
-            getcwd(pwd, sizeof(pwd));
+    freeCmd(cmd);
+    return status;
+}
+
+int runNormalCmd(Command *cmd) {
+    pid_t pid;
+    int status;
+    if (!strcmp(cmd->args[0], "exit")) {
+        printf("Good Bye, %s!\n", username);
+        exit(0);
+    } else if (!strcmp(cmd->args[0], "cd")) {
+        if (cmd->argc == 1) {
+            chdir(getenv("HOME"));
         } else {
-            if ((pid = fork()) == 0) {
-                // consider the redirection now
-                // it's just a part of normal command
-                // but not in other types
-                for (int i = 0; i < 3; i++) {
-                    if (cmd->redirectFD[i] != i) {
-                        close(i);
-                        dup2(cmd->redirectFD[i], i);
-                    } else if (cmd->redirectFile[i] != NULL) {
-                        int fd =
-                            open(cmd->redirectFile[i], O_RDWR | O_CREAT, 0666);
-                        if (fd < 0) {
-                            fprintf(stderr, "open file %s failed\n",
-                                    cmd->redirectFile[i]);
-                            exit(-1);
-                        }
-                        close(i);
-                        dup2(fd, i);
-                        close(fd);
-                    }
-                }
-                if (cmd->background) {
-                    setpgid(0, 0);
-                    // no output, redirect 1 and 2 to /dev/null
-                    int fd = open("/dev/null", O_RDWR);
-                    dup2(fd, 1);
-                    dup2(fd, 2);
-                    close(fd);
-                }
-                exit(execvp(cmd->args[0], cmd->args));
-            } else {
-                if (!cmd->background) {
-                    waitpid(pid, &status, 0);
-                    if (!WIFEXITED(status)) {
-                        // when here, the child process exited abnormally
-                        fprintf(stderr, "Process %d exited with status %d\n",
-                                pid, WEXITSTATUS(status));
-                    }
+            chdir(cmd->args[1]);
+        }
+        printf("\r");
+        getcwd(pwd, sizeof(pwd));
+    } else {
+        if ((pid = fork()) == 0) {
+            // consider the redirection now
+            // it's just a part of normal command
+            // but not in other types
+            redirect(cmd);
+            exit(execvp(cmd->args[0], cmd->args));
+        } else {
+            if (!cmd->background) {
+                waitpid(pid, &status, 0);
+                if (!WIFEXITED(status)) {
+                    // when here, the child process exited abnormally
+                    fprintf(stderr, "Process %d exited with status %d\n", pid,
+                            WEXITSTATUS(status));
                 }
             }
-            // return the exit status of the child process
-            return WEXITSTATUS(status);
-        }
-    } else if (cmd->type == CMD_PIPE) {
-        // create a pipe file and gets two file descriptors
-        // fd[0] is the read end, while fd[1] the write end
-        int fd[2];
-        pid_t left, right;
-        pipe(fd);
-        if ((left = fork()) == 0) {
-            /*
-             * close the read end of the pipe, so that the child process
-             * can only write to it; then redirect the standard output
-             * to the write end of the pipe, and close the write end
-             * itself as a file descriptor.
-             */
-            close(fd[0]);
-            dup2(fd[1], 1);
-            close(fd[1]);
-            exit(runcmd(cmd->left));
         }
-        if ((right = fork()) == 0) {
-            close(fd[1]);
-            dup2(fd[0], 0);
-            close(fd[0]);
-            exit(runcmd(cmd->right));
-        }
-        // close the pipe, because the parent process doesn't need it
-        // and wait for the two child processes to exit
+        // return the exit status of the child process
+        return WEXITSTATUS(status);
+    }
+}
+
+int runPipeCmd(Command *cmd) {
+    int status;
+    // create a pipe file and gets two file descriptors
+    // fd[0] is the read end, while fd[1] the write end
+    int fd[2];
+    pid_t left, right;
+    pipe(fd);
+    if ((left = fork()) == 0) {
+        /*
+         * close the read end of the pipe, so that the child process
+         * can only write to it; then redirect the standard output
+         * to the write end of the pipe, and close the write end
+         * itself as a file descriptor.
+         */
         close(fd[0]);
+        dup2(fd[1], 1);
+        close(fd[1]);
+        exit(runCmd(cmd->left));
+    }
+    if ((right = fork()) == 0) {
         close(fd[1]);
-        waitpid(left, NULL, 0);
-        waitpid(right, NULL, 0);
-    } else if (cmd->type == CMD_AND) {
+        dup2(fd[0], 0);
+        close(fd[0]);
+        exit(runCmd(cmd->right));
+    }
+    // close the pipe, because the parent process doesn't need it
+    // and wait for the two child processes to exit
+    close(fd[0]);
+    close(fd[1]);
+    waitpid(left, NULL, 0);
+    waitpid(right, NULL, 0);
+}
+
+int runAndOrCmd(Command *cmd) {
+    int status;
+    if (cmd->type == CMD_AND) {
         if (fork() == 0) {
-            exit(runcmd(cmd->left));
+            exit(runCmd(cmd->left));
         } else {
             waitpid(-1, &status, 0);
             if (WIFEXITED(status) && WEXITSTATUS(status) == 0 && fork() == 0) {
-                status = runcmd(cmd->right);
+                status = runCmd(cmd->right);
             }
             wait(NULL);
         }
     } else if (cmd->type == CMD_OR) {
         if (fork() == 0) {
-            exit(runcmd(cmd->left));
+            exit(runCmd(cmd->left));
         } else {
             waitpid(-1, &status, 0);
             if (WIFEXITED(status) && WEXITSTATUS(status) != 0 && fork() == 0) {
-                status = runcmd(cmd->right);
+                status = runCmd(cmd->right);
             }
             wait(NULL);
         }
     }
-    freecmd(cmd);
-    return status;
 }
 
-void freecmd(Command *cmd) {
+void redirect(Command *cur) {
+    int fd;
+    char *rfile;
+    for (int i = 0; i < 3; i++) {
+        fd = cur->redirectFD[i];
+        rfile = cur->redirectFile[i];
+        if (fd < -1 || fd > 2) {
+            fprintf(stderr, "file descriptor %d is invalid\n", fd);
+            exit(1);
+        }
+        if (fd == i && rfile == NULL) {
+            continue;
+        }
+        if (fd == -1) {
+            // append
+            fd = open(rfile, O_WRONLY | O_CREAT | O_APPEND, 0666);
+        } else if (rfile != NULL) {
+            // normal redirection
+            fd = open(rfile, O_WRONLY | O_CREAT | O_TRUNC, 0666);
+        } else {
+            // file descriptor redirection
+            // when here, fd is surely in 0, 1, 2
+            ;
+        }
+
+        if (fd < 0) {
+            fprintf(stderr, "open file %s failed\n", rfile);
+            exit(1);
+        }
+        close(i);
+        dup2(fd, i);
+        close(fd);
+    }
+}
+
+void freeCmd(Command *cmd) {
     if (cmd == NULL) {
         return;
     }
     if (cmd->left != NULL) {
-        freecmd(cmd->left);
+        freeCmd(cmd->left);
     }
     if (cmd->right != NULL) {
-        freecmd(cmd->right);
+        freeCmd(cmd->right);
     }
     int i;
     for (i = 0; i < cmd->argc; i++) {