From 42139b44eb4d953b5eac8182673db25e66c58018 Mon Sep 17 00:00:00 2001
From: Santiago Lo Coco <slococo@itba.edu.ar>
Date: Wed, 27 Oct 2021 22:15:13 -0300
Subject: [PATCH] Finish implementing pipes

Co-authored-by: Ezequiel Bellver <ebellver@itba.edu.ar>
Co-authored-by: Juan Barmasch <jbarmasch@itba.edu.ar>
---
 Kernel/asm/interrupts.asm                     |  22 ++++
 Kernel/include/pipeLib.h                      |   7 +-
 Kernel/include/schedulerLib.h                 |   2 +-
 Kernel/include/semLib.h                       |   9 +-
 Kernel/interruptions/systemCalls.c            |  13 ++-
 Kernel/interruptions/systemCallsDispatcher.c  |   7 +-
 Kernel/utils/pipe.c                           |  99 ++++++++++++-----
 Kernel/utils/scheduler.c                      | 102 +++++++++---------
 Kernel/utils/sem.c                            |  22 ++--
 Userland/SampleCodeModule/asm/libasm.asm      |  23 +++-
 Userland/SampleCodeModule/include/system.h    |   1 +
 Userland/SampleCodeModule/libc.c              |  29 ++++-
 .../SampleCodeModule/shell/commands/nice.c    |  11 ++
 .../shell/commands/printmem.c                 |   1 +
 Userland/SampleCodeModule/shell/commands/ps.c |   1 +
 .../shell/commands/quadratic.c                |   1 +
 .../SampleCodeModule/shell/commands/semCom.c  |   1 +
 .../SampleCodeModule/shell/commands/time.c    |   1 +
 .../SampleCodeModule/shell/include/nice.h     |  11 ++
 Userland/SampleCodeModule/shell/shell.c       |  43 ++++++--
 20 files changed, 288 insertions(+), 118 deletions(-)
 create mode 100644 Userland/SampleCodeModule/shell/commands/nice.c
 create mode 100644 Userland/SampleCodeModule/shell/include/nice.h

diff --git a/Kernel/asm/interrupts.asm b/Kernel/asm/interrupts.asm
index ddf5f71..06760ff 100755
--- a/Kernel/asm/interrupts.asm
+++ b/Kernel/asm/interrupts.asm
@@ -170,6 +170,13 @@ picSlaveMask:
 ;8254 Timer (Timer Tick)
 _irq00Handler:
 	pushState
+
+	; mov rsi, rsp
+	; and rsp, -16
+	; sub rsp, 108
+	; fsave [rsp]
+	; push rsi
+	
 	; push rax
 	; call getFPUaddress
 	; fsave [rax]
@@ -199,6 +206,14 @@ _irq00Handler:
 	; call getSSEaddress
 	; fxrstor [rax]
 	; pop rax
+	
+	; mov rax, rsp
+	; pop rsp
+	; and rsp, -16
+	; sub rsp, 108
+	; frstor [rsp]
+	; mov rsp, rax
+
 	popState
 	iretq
 
@@ -284,6 +299,13 @@ _initialize_stack_frame:
 	mov rdi, rdx 
 
     pushState
+
+	; mov rsi, rsp
+	; and rsp, -16
+	; sub rsp, 108
+	; fsave [rsp]
+	; push rsi
+
 	; fsave [bytesForFPU]
 	; push rax
 	; mov dword [auxi], 1
diff --git a/Kernel/include/pipeLib.h b/Kernel/include/pipeLib.h
index 2f62fd4..a175031 100644
--- a/Kernel/include/pipeLib.h
+++ b/Kernel/include/pipeLib.h
@@ -8,9 +8,10 @@
 
 typedef struct pipe_t {
     int fd[2];
-    char buffer[PIPE_MAX_SIZE];
-    int current;
-    char name[MAX_NAME];
+    char * buffer;
+    int currentR;
+    int currentW;
+    char * name;
     sem_t * sem;
 } pipe_t;
 
diff --git a/Kernel/include/schedulerLib.h b/Kernel/include/schedulerLib.h
index d7f7efc..f3ab205 100644
--- a/Kernel/include/schedulerLib.h
+++ b/Kernel/include/schedulerLib.h
@@ -9,7 +9,7 @@ char block(int pid);
 char unblock(int pid);
 char kill(int pid);
 void exitProcess();
-char nice(char offset);
+char nice(int pid, char offset);
 int getPid();
 char quitCPU();
 char * processes();
diff --git a/Kernel/include/semLib.h b/Kernel/include/semLib.h
index c2277b5..0f26211 100644
--- a/Kernel/include/semLib.h
+++ b/Kernel/include/semLib.h
@@ -10,14 +10,15 @@ typedef struct pid_t {
 
 typedef struct sem_t {
     unsigned int value;
-    char name[MAX_NAME];
+    // char name[MAX_NAME];
+    char * name;
     pid_t * entering;
     pid_t * last;
 } sem_t;
 
 sem_t * semOpen(char * name, unsigned int value);
-int semClose(sem_t * sem);
-int semWait(sem_t * sem);
-int semPost(sem_t * sem);
+char semClose(sem_t * sem);
+void semWait(sem_t * sem);
+void semPost(sem_t * sem);
 
 #endif
\ No newline at end of file
diff --git a/Kernel/interruptions/systemCalls.c b/Kernel/interruptions/systemCalls.c
index 5ab3015..d7eeb06 100644
--- a/Kernel/interruptions/systemCalls.c
+++ b/Kernel/interruptions/systemCalls.c
@@ -21,8 +21,8 @@ uint64_t write(uint64_t fd, uint64_t buffer, uint64_t length) {
 
     if (fd != STDOUT) {
         int i = 0;
-	    while (bufferAux[i] != '\0' && i++ <= length) {
-            writePipe(fd, bufferAux[i]);
+	    while (bufferAux[i] != '\0' && i <= length) {
+            writePipe(fd, bufferAux[i++]);
         }
         return i;
     }
@@ -46,8 +46,13 @@ uint64_t read(uint64_t fd, uint64_t buffer, uint64_t length) {
         }
     }
     else {
-        fd = getFdIn();
-        readBytes += strcpy(buffer, readPipe(fd));
+        while (length-- > 0) {
+            *bufferAux = readPipe(fd);
+            if (*bufferAux == 0)
+                break;
+            bufferAux++;
+            readBytes++;
+        }
     }
 
 	return readBytes;
diff --git a/Kernel/interruptions/systemCallsDispatcher.c b/Kernel/interruptions/systemCallsDispatcher.c
index a426369..f4ad6a1 100644
--- a/Kernel/interruptions/systemCallsDispatcher.c
+++ b/Kernel/interruptions/systemCallsDispatcher.c
@@ -7,6 +7,7 @@ void exitProcess();
 char * processes();
 void enqueueProcess(uint64_t, uint64_t, uint64_t, uint64_t, uint64_t);
 char openPipe(int *, char *);
+char nice(int, char);
 
 uint64_t systemCallsDispatcher(uint64_t rdi, uint64_t rsi, uint64_t rdx, uint64_t rcx, uint64_t r8, uint64_t r9) {
 	switch (rdi) {
@@ -31,12 +32,14 @@ uint64_t systemCallsDispatcher(uint64_t rdi, uint64_t rsi, uint64_t rdx, uint64_
         case 7:
             return (uint64_t) getSems();
         case 8:
-            return pvPortMalloc(rsi);
+            return pvPortMalloc((void *) rsi);
         case 9:
-            vPortFree(rsi);
+            vPortFree((void *) rsi);
             break;
         case 10:
             return (uint64_t) openPipe(rsi, rdx);
+        case 11:
+            return nice(rsi, rdx);
         default:
             return -1;
 	}
diff --git a/Kernel/utils/pipe.c b/Kernel/utils/pipe.c
index c488454..c3b74cc 100644
--- a/Kernel/utils/pipe.c
+++ b/Kernel/utils/pipe.c
@@ -1,42 +1,102 @@
 #include "pipe.h"
 
-int fds = 2;
+static int fdIndex = 2;
 
 node_t * firstPipe;
 
-char openPipe(int fds[2] ,char * name) {
+char openPipe(int fds[2], char * name) {
     pipe_t * pipe = pvPortMalloc(sizeof(pipe_t));
+    pipe->name = pvPortMalloc(MAX_NAME);
+    pipe->buffer = pvPortMalloc(PIPE_MAX_SIZE);
     strcpy(pipe->name, name);
     
     if ((pipe->sem = semOpen(SEM_NAME, 1)) == NULL)
         return EXIT_FAILURE;
 
-    pipe->fd[0] = fds++;
-    pipe->fd[1] = fds++;
+    node_t * node = pvPortMalloc(sizeof(node_t));
+    node->pipe = pipe;
+    node->next = firstPipe;
+    firstPipe = node;
+
+    pipe->currentR = 0;
+    pipe->currentW = 0;
+    pipe->fd[0] = fdIndex++;
+    pipe->fd[1] = fdIndex++;
     fds[0] = pipe->fd[0];
     fds[1] = pipe->fd[1];
 
     return EXIT_SUCCESS;
 }
 
+node_t * searchPipe(node_t ** previous, int fd) {
+    node_t * curr = firstPipe;
+    * previous = NULL;
+    while (curr != NULL) {
+        if (curr->pipe->fd[0] == fd || curr->pipe->fd[1] == fd) {
+            break;
+        }
+        * previous = curr;
+        curr = curr->next;
+    }
+    if (curr == NULL) {
+        * previous = NULL;
+        return NULL;
+    }
+    return curr;
+}
+
+node_t * searchWPipe(node_t ** previous, int fd) {
+    node_t * curr = firstPipe;
+    * previous = NULL;
+    while (curr != NULL) {
+        if (curr->pipe->fd[1] == fd) {
+            break;
+        }
+        * previous = curr;
+        curr = curr->next;
+    }
+    if (curr == NULL) {
+        * previous = NULL;
+        return NULL;
+    }
+    return curr;
+}
+
+node_t * searchRPipe(node_t ** previous, int fd) {
+    node_t * curr = firstPipe;
+    * previous = NULL;
+    while (curr != NULL) {
+        if (curr->pipe->fd[0] == fd) {
+            break;
+        }
+        * previous = curr;
+        curr = curr->next;
+    }
+    if (curr == NULL) {
+        * previous = NULL;
+        return NULL;
+    }
+    return curr;
+}
+
 void writePipe(int fd, char c) {
     node_t * prev = NULL;
-    node_t * node = searchPipe(&prev, fd);
+    node_t * node = searchWPipe(&prev, fd);
 
     semWait(node->pipe->sem);
 
-    node->pipe->buffer[node->pipe->current++ % PIPE_MAX_SIZE] = c;
+    node->pipe->buffer[node->pipe->currentW++ % PIPE_MAX_SIZE] = c;
 
     semPost(node->pipe->sem);
 }
 
 char readPipe(int fd) {
     node_t * prev = NULL;
-    node_t * node = searchPipe(&prev, fd);
+    node_t * node = searchRPipe(&prev, fd);
 
     semWait(node->pipe->sem);
 
-    char c = node->pipe->buffer[node->pipe->current-- % PIPE_MAX_SIZE];
+    char c = node->pipe->buffer[node->pipe->currentR++ % PIPE_MAX_SIZE];
 
     semPost(node->pipe->sem);
 
@@ -54,25 +114,10 @@ void closePipe(int fd) {
         prev->next = del->next;
     else firstPipe = del->next;
 
+    semClose(del->pipe->sem);
+    vPortFree(del->pipe->fd);
+    vPortFree(del->pipe->name);
+    vPortFree(del->pipe->buffer);
     vPortFree(del->pipe);
     vPortFree(del);
-    
-    semPost(del->pipe->sem);
-}
-
-node_t * searchPipe(node_t ** previous, int fd) {
-    node_t * curr = firstPipe;
-    * previous = NULL;
-    while (curr != NULL) {
-        if (curr->pipe->fd == fd) {
-            break;
-        }
-        * previous = curr;
-        curr = curr->next;
-    }
-    if (curr == NULL) {
-        * previous = NULL;
-        return NULL;
-    }
-    return curr;
 }
\ No newline at end of file
diff --git a/Kernel/utils/scheduler.c b/Kernel/utils/scheduler.c
index 2b15fda..2d4eb5c 100644
--- a/Kernel/utils/scheduler.c
+++ b/Kernel/utils/scheduler.c
@@ -22,6 +22,27 @@ typedef struct processCDT {
     // void * fpuBytes;
 } processCDT;
 
+// typedef long Align;
+
+// typedef union processCDT {
+//  struct {
+//     struct p * next;
+//     char * name;
+//     int pid;
+//     int ppid;
+//     uint64_t rsp;
+//     uint64_t rbp;
+//     char priority;
+//     char executions;
+//     char foreground;
+//     enum states state;
+//     int * fd;
+//     void * sseBytes;
+//     void * fpuBytes;
+//  } p;
+//  Align x;
+// } processCDT;
+
 processCDT * firstReady = NULL;
 processCDT * lastReady = NULL;
 processCDT * firstBlocked = NULL;
@@ -72,7 +93,7 @@ void initScheduler() {
 // void enqueueProcess(void (*fn) (int, char **), char foreground, int argc, char *argv[]) {
 void enqueueProcess(void (*fn) (int, char **), char foreground, int argc, char *argv[], int * fd) {
     if (fd == NULL) {
-        int * aux = pvPortMalloc(2);
+        int * aux = pvPortMalloc(2 * sizeof(int));
         aux[0] = 0;
         aux[1] = 1;
         fd = aux;
@@ -105,6 +126,7 @@ void enqueueProcess(void (*fn) (int, char **), char foreground, int argc, char *
     process->foreground = foreground;
     process->state = READY;
     process->fd = fd;
+    process->next = NULL;
     // process->sseBytes = pvPortMalloc(64);
     // process->fpuBytes = pvPortMalloc(14);
 
@@ -207,21 +229,28 @@ char kill(int pid) {
         if (del == NULL)
             return EXIT_FAILURE;
         else {
-            if (prev != NULL)
+            if (prev != NULL) {
                 prev->next = del->next;
+                if (del == lastBlocked)
+                    lastBlocked = prev;
+            }
             else
                 firstBlocked = del->next;
         }
     }
     else {
-        if (prev != NULL)
+        if (prev != NULL) {
             prev->next = del->next;
+            if (del == lastReady)
+                lastReady = prev;
+        }
         else
             firstReady = del->next;
     }
 
     processCDT * next = del->next;
 
+    vPortFree(del->fd);
     vPortFree((void *) del->rbp - STACK_SIZE);
     vPortFree((void *) del);
 
@@ -250,10 +279,22 @@ void exitProcess() {
     kill(currentProcess->pid);
 }
 
-char nice(char offset) {
-    if (currentProcess == NULL)
+char nice(int pid, char offset) {
+    if (offset >= 20 || offset < -20)
         return EXIT_FAILURE;
-    currentProcess->priority += offset;
+
+    processADT prev = NULL;
+    processADT del = searchProcess(&prev, pid, firstReady);
+    if (del == NULL) {
+        del = searchProcess(&prev, pid, firstBlocked);
+        if (del == NULL)
+            return EXIT_FAILURE;
+        else 
+            del->priority = offset + 20;
+    }
+    else {
+        del->priority = offset + 20;
+    }
     return EXIT_SUCCESS;
 }
 
@@ -280,7 +321,7 @@ char quitCPU() {
     return EXIT_SUCCESS;
 }
 
-char getGenProcessData(char ** out, char * written, char toAdd, char * in, char isLast) {
+void getGenProcessData(char ** out, char * written, char toAdd, char * in, char isLast) {
     char copied = strcpy(*out, in);
     *out += copied;
     *out += addSpaces(*out, toAdd - copied);
@@ -313,44 +354,10 @@ char getProcessData(char * out, processCDT * proc) {
     
     char buffer[10];
     getGenProcessData(&out, &written, MAX_ATTR_SIZE, itoa(proc->pid, buffer, 10, 10), 0);
-    // char copied = strcpy(out, itoa(proc->pid, buffer, 10, 10));
-    // out += copied;
-    // out += addSpaces(out, MAX_ATTR_SIZE - copied);
-    // written += MAX_ATTR_SIZE;
-    // out += addSpaces(out, 2);
-    // written += 2;
-
     getGenProcessData(&out, &written, MAX_ATTR_SIZE, itoa(proc->priority, buffer, 10, 2), 0);
-    // copied = strcpy(out, itoa(proc->priority, buffer, 10, 2));
-    // out += copied;
-    // out += addSpaces(out, MAX_ATTR_SIZE - copied);
-    // written += MAX_ATTR_SIZE;
-    // out += addSpaces(out, 2);
-    // written += 2;
-
     getGenProcessData(&out, &written, MAX_NAME_SIZE, itoa(proc->rsp, buffer, 16, 10), 0);
-    // copied = strcpy(out, itoa(proc->rsp, buffer, 16, 10));
-    // out += copied;
-    // out += addSpaces(out, MAX_NAME_SIZE - copied);
-    // written += MAX_NAME_SIZE;
-    // out += addSpaces(out, 2);
-    // written += 2;
-
     getGenProcessData(&out, &written, MAX_NAME_SIZE, itoa(proc->rbp, buffer, 16, 10), 0);
-    // copied = strcpy(out, itoa(proc->rbp, buffer, 16, 10));
-    // out += copied;
-    // out += addSpaces(out, MAX_NAME_SIZE - copied);
-    // written += MAX_NAME_SIZE;
-    // out += addSpaces(out, 2);
-    // written += 2;
-
     getGenProcessData(&out, &written, MAX_ATTR_SIZE, (proc->foreground == 1) ? "F" : "B", 1);
-    // *out++ = (proc->foreground == 1) ? 'F' : 'B';
-    // out += addSpaces(out, MAX_ATTR_SIZE - 1);
-    // written += MAX_ATTR_SIZE;
-
-    // out += addSpaces(out, 2);
-    // written += 2;
     
     return written;
 }
@@ -381,15 +388,4 @@ char * processes(){
     *--ans = 0;
 
     return ret;
-}
-
-/*
-● Crear un proceso. DEBERÁ soportar el pasaje de parámetros. LISTO
-● Obtener el ID del proceso que llama. LISTO
-● Listar todos los procesos: nombre, ID, prioridad, stack y base pointer, foreground y
-cualquier otra variable que consideren necesaria. LISTO
-● Matar un proceso arbitrario. LISTO
-● Modificar la prioridad de un proceso arbitrario.  LISTO
-● Bloquear y desbloquear un proceso arbitrario. LISTO
-● Renunciar al CPU. LISTO
-*/
\ No newline at end of file
+}
\ No newline at end of file
diff --git a/Kernel/utils/sem.c b/Kernel/utils/sem.c
index 0c128aa..2f26b6a 100644
--- a/Kernel/utils/sem.c
+++ b/Kernel/utils/sem.c
@@ -7,7 +7,7 @@ typedef struct node_t {
     struct node_t * next;
 } node_t;
 
-static sem_t semaphores[MAX_SEM];
+// static sem_t semaphores[MAX_SEM];
 node_t * firstSem = NULL;
 static char counter = 0;
 
@@ -19,14 +19,17 @@ sem_t * semOpen(char * name, unsigned int value) {
     node->sem = sem;
     node->next = firstSem;    
     firstSem = node;
+    sem->name = pvPortMalloc(MAX_NAME);
     strcpy(sem->name, name);
     sem->value = value;
     counter++;
 
     leave_region(&semLock);
+
+    return sem;
 }
 
-int semClose(sem_t * sem) {
+char semClose(sem_t * sem) {
     if (sem == NULL)
         return EXIT_FAILURE;
 
@@ -34,7 +37,7 @@ int semClose(sem_t * sem) {
 
     node_t * del = NULL;
 
-    if (firstSem == sem) {
+    if (firstSem->sem == sem) {
         del = firstSem;
         firstSem = firstSem->next;
     }
@@ -62,14 +65,17 @@ int semClose(sem_t * sem) {
         pid = pid->next;
         vPortFree(aux);
     }
+    vPortFree(sem->name);
     vPortFree(sem);
     vPortFree(del);
     
     counter--;
     leave_region(&semLock);
+
+    return EXIT_SUCCESS;
 }
 
-int semWait(sem_t * sem) {
+void semWait(sem_t * sem) {
     enter_region(&semLock);
 
     if (sem->value > 0) {
@@ -81,7 +87,10 @@ int semWait(sem_t * sem) {
         pid_t * curr = pvPortMalloc(sizeof(pid_t));
         curr->pid = getPid();
         curr->next = NULL;
-        sem->last->next = curr;
+        if (sem->entering == NULL)
+            sem->entering = curr;
+        if (sem->last != NULL)
+            sem->last->next = curr;
         sem->last = curr;
         block(curr->pid);
 
@@ -92,7 +101,7 @@ int semWait(sem_t * sem) {
     leave_region(&semLock);
 }
 
-int semPost(sem_t * sem) {
+void semPost(sem_t * sem) {
     enter_region(&semLock);
 
     sem->value++;
@@ -151,7 +160,6 @@ char * getSems() {
     
     char * info = "name       value   pidsWaiting\n";
     ans += strcpy(ans, info);
-    // ans += 56;
 
     node_t * aux = firstSem;
     while (aux != NULL) {
diff --git a/Userland/SampleCodeModule/asm/libasm.asm b/Userland/SampleCodeModule/asm/libasm.asm
index 3bd6bbe..e3a7607 100644
--- a/Userland/SampleCodeModule/asm/libasm.asm
+++ b/Userland/SampleCodeModule/asm/libasm.asm
@@ -3,7 +3,7 @@ GLOBAL _getMem, sys_loadProcess
 GLOBAL raiseOpcodeExc
 GLOBAL _getRegs, sys_switchContext
 GLOBAL cpu_id, cpu_id_support
-GLOBAL sys_exit, sys_ps, sys_free, sys_malloc, sys_sem, sys_openPipe
+GLOBAL sys_exit, sys_ps, sys_free, sys_malloc, sys_sem, sys_openPipe, sys_nice
 
 section .text
 
@@ -199,6 +199,27 @@ sys_sem:
     pop rbp
     ret
 
+sys_nice:
+    push rbp
+    mov rbp, rsp
+
+	push rdi
+	push rsi
+	push rdx
+
+	mov rdx, rsi
+	mov rsi, rdi
+	mov rdi, 11
+	int 80h
+
+	pop rdx
+	pop rsi
+	pop rdi
+
+    mov rsp, rbp
+    pop rbp
+    ret
+
 _getMem:
 	push rbp
 	mov rbp, rsp
diff --git a/Userland/SampleCodeModule/include/system.h b/Userland/SampleCodeModule/include/system.h
index 815d3db..a80da92 100644
--- a/Userland/SampleCodeModule/include/system.h
+++ b/Userland/SampleCodeModule/include/system.h
@@ -12,5 +12,6 @@ char * sys_sem();
 void * sys_malloc(int);
 void * sys_free(void *);
 void * sys_openPipe(int *, char *);
+char sys_nice(int, char);
 
 #endif
\ No newline at end of file
diff --git a/Userland/SampleCodeModule/libc.c b/Userland/SampleCodeModule/libc.c
index de703bd..7aa82f9 100644
--- a/Userland/SampleCodeModule/libc.c
+++ b/Userland/SampleCodeModule/libc.c
@@ -141,12 +141,31 @@ char* itoa(int value, char* buffer, int base) {
     return reverse(buffer, 0, i - 1);
 }
 
-int atoi(char * string, int length) {
-    int res = 0, i = 0;
-    while (i < length) {
-        res = res * 10 + string[i++] - '0';
+// int atoi(char * string, int length) {
+//     int res = 0, i = 0;
+//     while (string[i] != 0 && i < length) {
+//         res = res * 10 + string[i++] - '0';
+//     }
+//     return res;
+// }
+
+int atoi(char *str, int length) {
+    int i = 0, sign = 1, val = 0, nbr = 0;
+    while (str[i] != '\0') {
+        if (str[i] == '-') {
+            sign = -sign;
+            str++;
+        }
+        i++;
     }
-    return res;
+    i = 0;
+    while (str[i] >= '0' && str[i] <= '9' && str[i] != '\0') {
+        nbr = (int) (str[i] - '0');
+        val = (val * 10) + nbr;
+        i++;
+    }
+    i++;
+    return (val * sign);
 }
 
 int pow(int base, int exponent) {
diff --git a/Userland/SampleCodeModule/shell/commands/nice.c b/Userland/SampleCodeModule/shell/commands/nice.c
new file mode 100644
index 0000000..2771f98
--- /dev/null
+++ b/Userland/SampleCodeModule/shell/commands/nice.c
@@ -0,0 +1,11 @@
+#include "nice.h"
+
+void nice(int argc, char ** argv) {
+    if (argc != 3)
+        printStringLen("nice receives a pid and an offset\n", 35);
+    int pid = atoi(argv[1], MAX_LEN);
+    char offset = (char) atoi(argv[2], MAX_LEN);
+
+    sys_nice(pid, offset);
+    sys_exit();
+}
\ No newline at end of file
diff --git a/Userland/SampleCodeModule/shell/commands/printmem.c b/Userland/SampleCodeModule/shell/commands/printmem.c
index 4846f83..3f91936 100644
--- a/Userland/SampleCodeModule/shell/commands/printmem.c
+++ b/Userland/SampleCodeModule/shell/commands/printmem.c
@@ -30,4 +30,5 @@ void printmem(int argc, char *argv[]) {
 		printString(itoa(buffer[i], bufferAux, 16));
 		new_line();
 	}
+    sys_exit();
 }
\ No newline at end of file
diff --git a/Userland/SampleCodeModule/shell/commands/ps.c b/Userland/SampleCodeModule/shell/commands/ps.c
index 5221e29..21728c6 100644
--- a/Userland/SampleCodeModule/shell/commands/ps.c
+++ b/Userland/SampleCodeModule/shell/commands/ps.c
@@ -6,4 +6,5 @@ void ps(int argc, char *argv[]) {
     printString(output);
     new_line();
     sys_free(output);
+    sys_exit();
 }
\ No newline at end of file
diff --git a/Userland/SampleCodeModule/shell/commands/quadratic.c b/Userland/SampleCodeModule/shell/commands/quadratic.c
index 0e93e7c..f646fb0 100644
--- a/Userland/SampleCodeModule/shell/commands/quadratic.c
+++ b/Userland/SampleCodeModule/shell/commands/quadratic.c
@@ -40,4 +40,5 @@ void quadratic(int argc, char *argv[]) {
 	ftoa(sol2, buffer2, 10);
 	printString(buffer2);
     new_line();
+    sys_exit();
 }
\ No newline at end of file
diff --git a/Userland/SampleCodeModule/shell/commands/semCom.c b/Userland/SampleCodeModule/shell/commands/semCom.c
index f19764b..05dffb4 100644
--- a/Userland/SampleCodeModule/shell/commands/semCom.c
+++ b/Userland/SampleCodeModule/shell/commands/semCom.c
@@ -6,4 +6,5 @@ void sem(int argc, char *argv[]) {
     printString(output);
     new_line();
     sys_free(output);
+    sys_exit();
 }
\ No newline at end of file
diff --git a/Userland/SampleCodeModule/shell/commands/time.c b/Userland/SampleCodeModule/shell/commands/time.c
index 74d2d2a..5a79f5a 100644
--- a/Userland/SampleCodeModule/shell/commands/time.c
+++ b/Userland/SampleCodeModule/shell/commands/time.c
@@ -47,4 +47,5 @@ void time(int argc, char *argv[]) {
     printTime(getMinutes());
     putChar(':');
     printTime(getSeconds());
+    sys_exit();
 }
\ No newline at end of file
diff --git a/Userland/SampleCodeModule/shell/include/nice.h b/Userland/SampleCodeModule/shell/include/nice.h
new file mode 100644
index 0000000..d74ed99
--- /dev/null
+++ b/Userland/SampleCodeModule/shell/include/nice.h
@@ -0,0 +1,11 @@
+#ifndef NICE_LIB
+#define NICE_LIB
+
+#include "libc.h"
+#include "system.h"
+
+#define MAX_LEN 10
+
+void nice(int argc, char *argv[]);
+
+#endif
\ No newline at end of file
diff --git a/Userland/SampleCodeModule/shell/shell.c b/Userland/SampleCodeModule/shell/shell.c
index 2d9f91f..1710464 100644
--- a/Userland/SampleCodeModule/shell/shell.c
+++ b/Userland/SampleCodeModule/shell/shell.c
@@ -15,6 +15,7 @@
 #include "cat.h"
 #include "semCom.h"
 #include "stddef.h"
+#include "nice.h"
 #define EXIT_FAILURE 1
 #define EXIT_SUCCESS 0
 
@@ -30,7 +31,7 @@ typedef struct cmd_t {
     char isBuiltIn;
 } cmd_t;
 
-const int len = 14;
+const int len = 15;
 cmd_t commands[] = {
     { "help", help, 1 },
     { "cat", cat, 0 },
@@ -41,6 +42,7 @@ cmd_t commands[] = {
     { "filter", filter, 0 },
     { "clear", clear, 1 },
     { "cpufeatures", cpufeatures, 1 },
+    { "nice", nice, 0 },
     { "ps", ps, 1 },
     { "sem", sem, 1 },
     { "quadratic", quadratic, 0 },
@@ -82,34 +84,45 @@ void processInput(char * input) {
             break;
         }
     }
-    int fd[2];
+
+    int * fd, * fd1, * fd2;
+    fd1 = sys_malloc(2 * sizeof(int));
+    fd1[0] = 0;
+    fd1[1] = 1;
+
     if (pipe != -1) {
+        fd = sys_malloc(2 * sizeof(int));
         if (sys_openPipe(fd, "pipe"))
             return;
-            // return EXIT_FAILURE;
+        fd2 = sys_malloc(2 * sizeof(int));
+
+        fd1[0] = 0;
+        fd1[1] = fd[1];
+        fd2[0] = fd[0];
+        fd2[1] = 1;
     }
     char ** argv0 = NULL;
     char ** argv1 = NULL;
+    int comm0 = -1;
+    int comm1 = -1;
+
     if (pipe != -1) {
         argv0 = sys_malloc(sizeof(char *) * pipe);
         for (int i = 0; i < pipe; i++)
             argv0[i] = tokens[i];
         argv1 = sys_malloc(sizeof(char *) * (end - pipe - 1));
-        for (int i = pipe + 1; i < end - pipe - 1; i++)
-            argv1[i] = tokens[i];
+        for (int i = pipe + 1; i < end; i++)
+            argv1[i - pipe - 1] = tokens[i];
     }
     else {
-        *argv0 = sys_malloc(sizeof(char *) * end);
+        argv0 = sys_malloc(sizeof(char *) * end);
         for (int i = 0; i < end; i++)
             argv0[i] = tokens[i];
     }
     for (int i = 0; i < len; i++) {
         if (!strcmp(tokens[0], commands[i].name)) {
             comm_flag0 = 1;
-            if (pipe != -1)
-                sys_loadProcess(commands[i].func, 1, pipe, argv0, fd);
-            else 
-                sys_loadProcess(commands[i].func, 1, end, argv0, NULL);
+            comm0 = i;
             break;
         }
     }
@@ -117,12 +130,20 @@ void processInput(char * input) {
         for (int i = 0; i < len; i++) {
             if (!strcmp(tokens[pipe + 1], commands[i].name)) {
                 comm_flag1 = 1;
-                sys_loadProcess(commands[i].func, 1, end - pipe - 1, argv1, fd);
+                comm1 = i;
                 break;
             }
         }
     }
 
+    if (comm_flag0 && (comm_flag1 || pipe == -1)) {
+        if (pipe != -1) {
+            sys_loadProcess(commands[comm0].func, 1, pipe, argv0, fd1);
+            sys_loadProcess(commands[comm1].func, 1, end - pipe - 1, argv1, fd2);
+        }
+        else sys_loadProcess(commands[comm0].func, 1, end, argv0, fd1);
+    }
+
     if (!comm_flag0) {
         if (*tokens[0] != 0)
             incorrect_comm(tokens[0]);