From 68f5ff29c0aae1a176c25996aab0144badd0f092 Mon Sep 17 00:00:00 2001
From: Niklas Halle <niklas@niklashalle.net>
Date: Thu, 21 May 2020 19:46:13 +0200
Subject: you can now put stuff in the background, yay

---
 02_exercise/shell.c | 68 ++++++++++++++++++++++++++++++++---------------------
 1 file changed, 41 insertions(+), 27 deletions(-)

diff --git a/02_exercise/shell.c b/02_exercise/shell.c
index 1bdeab6..7032a99 100644
--- a/02_exercise/shell.c
+++ b/02_exercise/shell.c
@@ -1,4 +1,3 @@
-#include <fcntl.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
@@ -12,19 +11,19 @@
 int parse_line(char const *line, char ***parts, size_t *part_count);
 
 // returns the return code of the executed program
-int exec_command(const char *path, char *const argv[], unsigned timeout);
+int exec_command(const char *path, char *const argv[], bool background);
 
 int main(void) {
-    chdir(".");
     setvbuf(stdout, NULL, _IONBF, 0);
 
     char const *const original_wd = get_current_dir_name();
     char const *prompt = relative_path(original_wd, original_wd);
     bool done = false;
     while (!done) {
+        bool bg = false;
         char *line = NULL;
         size_t cap = 0;
-        __ssize_t length = 0;
+        __ssize_t length;
 
         printf("%s > ", prompt);
         if ((length = getline(&line, &cap, stdin)) < 0) {
@@ -42,7 +41,19 @@ int main(void) {
         size_t argument_count;
         parse_line(line, &arguments, &argument_count);
 
-        if (strcmp(arguments[0], "cd") == 0) {
+        if (argument_count <= 0)
+            goto clean;
+
+        char *command = arguments[0];
+        char *last_arg = arguments[argument_count - 2];
+
+        if (strcmp(last_arg, "&") == 0) {
+            bg = true;
+            arrayRelease(arguments[argument_count - 2]);
+            arguments[argument_count - 2] = NULL;
+        }
+
+        if (strcmp(command, "cd") == 0) {
             if (arrayLen(arguments) != 3) {
                 fprintf(stderr, "usage: cd <path>");
                 goto clean;
@@ -56,10 +67,10 @@ int main(void) {
             char const *current_wd = get_current_dir_name();
             prompt = relative_path(original_wd, current_wd);
             free((void *)current_wd);
-        } else if (strcmp(arguments[0], "exit") == 0) {
+        } else if (strcmp(command, "exit") == 0) {
             done = true;
         } else {
-            int ret = exec_command(arguments[0], arguments, 0);
+            int ret = exec_command(command, arguments, bg);
             if (ret)
                 printf("[%i] ", ret);
         }
@@ -111,19 +122,7 @@ int parse_line(char const *line, char ***parts, size_t *part_count) {
     return 0;
 }
 
-void print_prompt() {
-    size_t length = 1024;
-    char  *buffer = malloc(length * sizeof(char));
-    getcwd(buffer, length);
-    if (buffer == NULL) {
-        printf(".> ");
-    } else {
-        printf("%s > ", buffer);
-    }
-}
-
-int exec_command(const char *path, char *const argv[], unsigned timeout) {
-    timeout = timeout ^ timeout;
+int exec_command(const char *path, char *const argv[], bool background) {
     int  pid;
     int  pipefd[2];
     int  status;
@@ -132,7 +131,7 @@ int exec_command(const char *path, char *const argv[], unsigned timeout) {
     pipe(pipefd);
     if ((pid = fork()) == 0) {
         close(pipefd[0]);
-        dup2(pipefd[1], 1); // includes close(1);
+        dup2(pipefd[1], 1);
         close(pipefd[1]);
         execvp(path, argv);
         fprintf(stderr, "could not execute \"%s\"\n", path);
@@ -147,14 +146,29 @@ int exec_command(const char *path, char *const argv[], unsigned timeout) {
 
     close(pipefd[1]);
 
-    __ssize_t length = 0;
-    while ((length = read(pipefd[0], buf, 10)) > 0) {
-        buf[length] = '\0';
-        fprintf(stdout, "%s", buf);
-        fflush(stdout);
+    int new_pid;
+    if (background) {
+        new_pid = fork();
     }
 
-    waitpid(pid, &status, 0);
+    if (!background || new_pid == 0) {
+        if (background)
+            printf("[%i]\n", pid);
+
+        __ssize_t length;
+        while ((length = read(pipefd[0], buf, 10)) > 0) {
+            buf[length] = '\0';
+            printf("%s", buf);
+        }
+
+        waitpid(pid, &status, 0);
+
+        if (background) {
+            printf("[%i] TERMINATED\n", pid);
+            printf("[%i] EXIT STATUS: %i\n", pid, status);
+            exit(0);
+        }
+    }
 
     close(pipefd[0]);
 
-- 
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