From 74abc79434fe895d0ca863e4d1d6c5c16b54f296 Mon Sep 17 00:00:00 2001
From: Niklas Halle <niklas@niklashalle.net>
Date: Mon, 1 Jun 2020 15:46:28 +0200
Subject: trying to connect server and shell, weird

---
 03_exercise/srv/process.c | 169 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 169 insertions(+)
 create mode 100644 03_exercise/srv/process.c

(limited to '03_exercise/srv/process.c')

diff --git a/03_exercise/srv/process.c b/03_exercise/srv/process.c
new file mode 100644
index 0000000..c5be8c3
--- /dev/null
+++ b/03_exercise/srv/process.c
@@ -0,0 +1,169 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <wait.h>
+
+#include "array.h"
+#include "process.h"
+
+
+// given a substring of a line tries to parse out as much information as possible
+int parse_command(char const *line, char const *end, process *p) {
+    char *part;
+    char **local_parts;
+    if (arrayInit(part) != 0 || arrayInit(local_parts) != 0) {
+        fprintf(stderr, "Failed to prepare new part / parts array whilst parsing line");
+        return -1;
+    }
+
+    for (size_t i = 0; line + i < end; ++i) {
+        char c;
+        switch (c = line[i]) {
+        default:
+            arrayPush(part) = c;
+            break;
+        case ' ':
+        case '\t':
+        case '\0':
+            if (arrayLen(part) == 0)
+                continue;
+
+            arrayPush(part) = '\0';
+            arrayPush(local_parts) = part;
+            arrayInit(part);
+        }
+    }
+
+    if (arrayLen(part) == 0) {
+        arrayRelease(part);
+    } else {
+        arrayPush(part) = '\0';
+        arrayPush(local_parts) = part;
+    }
+
+    arrayPush(local_parts) = NULL;
+    p->argc = arrayLen(local_parts) - 1;
+    p->argv = local_parts;
+
+    return 0;
+}
+
+int parse_line(char const *const line, process **processes) {
+    // splits the line at | and then parses the commands
+    int ret_code;
+
+    if (arrayInit(*processes) != 0) {
+        perror("Failed to initialize processes array");
+        return -1;
+    }
+
+    bool done = false;
+    char const *cursor = line;
+    while (!done) {
+        process p = {.argv = NULL, .argc = 0, .in_fd = 0, .out_fd = 0, .pid = 0, .blocking = true};
+        char const *end = strchr(cursor, '|');
+
+        if (end == NULL) {
+            done = true;
+            end = line + strlen(line);
+        }
+
+        if ((ret_code = parse_command(cursor, end, &p)) != 0) {
+            return ret_code;
+        }
+
+        arrayPush(*processes) = p;
+        cursor = end + 1;
+    }
+
+    size_t  p_len = arrayLen(*processes);
+    process *last = *processes + (p_len - 1);
+
+    // linking up all processes as we currently only have pipes for multiple commands
+    for (size_t i = 0; i < p_len - 1; ++i) {
+        int fds[2];
+        if (pipe(fds) != 0) {
+            perror("Failed to create pipe");
+            return -1;
+        }
+        (*processes)[i].out_fd = fds[1];
+        (*processes)[i + 1].in_fd = fds[0];
+    }
+
+    // setting all processes to non blocking when
+    if (strcmp(last->argv[last->argc - 1], "&") == 0) {
+        arrayPop(last->argv) = NULL;
+        last->argc = last->argc - 1;
+        last->argv[last->argc] = NULL;
+
+        for (size_t i = 0; i < p_len; ++i) {
+            (*processes)[i].blocking = false;
+        }
+    }
+
+    return ret_code;
+}
+
+int exec_command(process p) {
+    int status;
+
+    if ((p.pid = fork()) == 0) {
+        if (p.in_fd != 0) {
+            dup2(p.in_fd, 0);
+            close(p.in_fd);
+        }
+        if(p.in_fd == 0 && !p.blocking) {
+            close(0);
+        }
+
+        if (p.out_fd != 0) {
+            dup2(p.out_fd, 1);
+            close(p.out_fd);
+        }
+
+        execvp(p.argv[0], p.argv);
+        fprintf(stderr, "command not found: \"%s\"\n", p.argv[0]);
+        fflush(stderr);
+        exit(-1);
+    }
+
+    if (p.pid < 0) {
+        fprintf(stderr, "no fork\n");
+        exit(-2);
+    }
+
+    if (p.in_fd != 0) {
+        close(p.in_fd);
+    }
+
+    if (p.out_fd != 0) {
+        close(p.out_fd);
+    }
+
+    if (!p.blocking)
+        printf("[%i]\n", p.pid);
+
+    if (waitpid(p.pid, &status, p.blocking ? 0 : WNOHANG) < 0) {
+        fprintf(stderr, "wait error'ed out\n");
+    }
+
+    return WEXITSTATUS(status);
+}
+
+void free_processes(process **pr) {
+    process *processes = *pr;
+    while (!arrayIsEmpty(processes)) {
+        process p = arrayPop(processes);
+        while (!arrayIsEmpty(p.argv)) {
+            char *tmp = arrayTop(p.argv);
+            if (tmp) {
+                arrayRelease(tmp);
+            }
+            arrayPop(p.argv) = NULL;
+        }
+        arrayRelease(p.argv);
+    }
+    arrayRelease(processes);
+    *pr = NULL;
+}
\ No newline at end of file
-- 
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