From 922b46952d38f51850640a20d7be4747e84e95f4 Mon Sep 17 00:00:00 2001
From: Niklas Halle <niklas@niklashalle.net>
Date: Sun, 24 May 2020 17:08:04 +0200
Subject: implemented a basic wait, not much tests yet, some functionality
 missing

---
 02_exercise/process.c | 14 +------------
 02_exercise/shell.c   | 56 ++++++++++++++++++++++++++++++++++++++++++++-------
 2 files changed, 50 insertions(+), 20 deletions(-)

diff --git a/02_exercise/process.c b/02_exercise/process.c
index fb55236..95a0600 100644
--- a/02_exercise/process.c
+++ b/02_exercise/process.c
@@ -107,12 +107,6 @@ int parse_line(char const *const line, process **processes) {
 int exec_command(process p) {
     int status;
 
-    if (!p.blocking) {
-        // if the process is to be put in the background let a fork handle it
-        if (fork() != 0)
-            return 0;
-    }
-
     if ((p.pid = fork()) == 0) {
         if (p.in_fd != 0) {
             dup2(p.in_fd, 0);
@@ -146,16 +140,10 @@ int exec_command(process p) {
     if (!p.blocking)
         printf("[%i]\n", p.pid);
 
-    if (waitpid(p.pid, &status, 0) < 0) {
+    if (waitpid(p.pid, &status, p.blocking ? 0 : WNOHANG) < 0) {
         fprintf(stderr, "wait error'ed out\n");
     }
 
-    if (!p.blocking) {
-        printf("[%i] TERMINATED\n", p.pid);
-        printf("[%i] EXIT STATUS: %i\n", p.pid, status); // TODO: exit status is wrong
-        exit(0);
-    }
-
     return WEXITSTATUS(status);
 }
 
diff --git a/02_exercise/shell.c b/02_exercise/shell.c
index ea1b13f..35de455 100644
--- a/02_exercise/shell.c
+++ b/02_exercise/shell.c
@@ -3,14 +3,14 @@
 #include <string.h>
 #include <unistd.h>
 #include <stdbool.h>
+#include <wait.h>
 
 #include "array.h"
 #include "process.h"
 #include "prompt_utils.h"
 
-
 int main(void) {
-    chdir(".");
+    setvbuf(stderr, NULL, _IONBF, 0);
     setvbuf(stdout, NULL, _IONBF, 0);
 
     char const *const original_wd = get_current_dir_name();
@@ -24,6 +24,7 @@ int main(void) {
         printf("%s > ", prompt);
         if ((length = getline(&line, &cap, stdin)) < 0) {
             fprintf(stderr, "Failed to read from STDIN");
+            fflush(stderr);
             exit(-1);
         }
 
@@ -41,12 +42,20 @@ int main(void) {
                 perror("Can't chain cd with other processes");
             }
 
-            if (arrayLen(processes[0].argv) != 3) {
-                fprintf(stderr, "usage: cd <path>");
-                goto clean;
+            int ret;
+            switch(arrayLen(processes[0].argv)) {
+                case 3:
+                    ret = chdir(processes[0].argv[1]);
+                    break;
+                case 2:
+                    ret = chdir(original_wd);
+                    break;
+                default:
+                    fprintf(stderr, "usage: cd <path>\n");
+                    fflush(stderr);
+                    ret = -1;
             }
 
-            int ret = chdir(processes[0].argv[1]);
             if (ret)
                 printf("[%i] ", ret);
 
@@ -56,6 +65,40 @@ int main(void) {
             free((void *)current_wd);
         } else if (strcmp(processes[0].argv[0], "exit") == 0) {
             done = true;
+        } else if (strcmp(processes[0].argv[0], "wait") == 0) {
+            bool error = false;
+            pid_t *pids;
+            arrayInit(pids);
+            size_t i = 1;
+            while (!error && processes[0].argv[i] != NULL) {
+                char *end;
+                pid_t tmp = strtol(processes[0].argv[i], &end, 10);
+                if (*end != '\0') {
+                    fprintf(stderr, "Not a valid pid: %s", processes[0].argv[i]);
+                    error = true;
+                    break;
+                }
+                arrayPush(pids) = tmp;
+                ++i;
+            }
+
+            if (!error) {
+                while (!arrayIsEmpty(pids)) {
+                    int status;
+                    pid_t current_pid = arrayPop(pids);
+                    printf("Waiting for %ld...\n", (long) current_pid);
+                    if (waitpid(current_pid, &status, WUNTRACED) < 0) {
+                        perror("Could not wait on process");
+                    } else {
+                        printf("[%i] TERMINATED\n", current_pid);
+                        printf("[%i] EXIT STATUS: %i\n", current_pid, status); // TODO: exit status is wrong
+                    }
+                    // TODO: catch ctrl-c
+                }
+            }
+
+            arrayRelease(pids);
+
         } else {
             for (size_t i = 0; i < arrayLen(processes); ++i) {
                 int ret = exec_command(processes[i]);
@@ -65,7 +108,6 @@ int main(void) {
 
         }
 
-        clean:
         free((void *)line);
         line = NULL;
         cap = 0;
-- 
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