Fix bugs, add .nushrc support, beautify prompt

- Fix char overflow in read_command (pointer_length -> size_t)
- Fix out-of-bounds read on empty PATH components
- Use _exit() instead of exit() in child after fork
- Add bounds check on symtab stack overflow
- Fix add_to_buf write-before-check and realloc failure corruption
- Fix include guard BACKEND_H -> EXECUTOR_H
- Stop redefining EOF from stdio (use SRC_EOF)
- Remove dead variable in source.c
- Replace deprecated cuserid with getpwuid(getuid())
- Add .nushrc loading on startup
- Beautify prompt: user@hostname:path $ with colors and ~ substitution

Author: ToastCoder

src/executor.c

@@ -37,7 +37,7 @@ char *search_path(char *file)
 	strncpy(path, p, p2-p);
         path[p2-p] = '\0';
 
-	if(p2[-1] != '/')
+	if(p2 > p && p2[-1] != '/')
         {
             strcat(path, "/");
         }
@@ -170,15 +170,15 @@ int do_simple_command(struct node_s *node)
         fprintf(stderr, "Error: Failed to execute command: %s\n", strerror(errno));
         if(errno == ENOEXEC)
         {
-            exit(126);
+            _exit(126);
         }
         else if(errno == ENOENT)
         {
-            exit(127);
+            _exit(127);
         }
         else
         {
-            exit(EXIT_FAILURE);
+            _exit(EXIT_FAILURE);
         }
     }
     else if(child_pid < 0)

src/executor.h

@@ -1,5 +1,5 @@
-#ifndef BACKEND_H
-#define BACKEND_H
+#ifndef EXECUTOR_H
+#define EXECUTOR_H
 
 #include "node.h"
 

src/initsh.c

@@ -1,5 +1,8 @@
+#include <stdio.h>
+#include <stdlib.h>
 #include <string.h>
 #include "shell.h"
+#include "source.h"
 #include "symtab/symtab.h"
 
 extern char **environ;
@@ -41,4 +44,55 @@ void initsh(void)
 
     entry = add_to_symtab("PS2");
     symtab_entry_setval(entry, "> ");
+
+    load_rc_file();
+}
+
+void load_rc_file(void)
+{
+    char *home = getenv("HOME");
+    if(!home) return;
+
+    size_t path_len = strlen(home) + 9;
+    char path[path_len];
+    strcpy(path, home);
+    strcat(path, "/.nushrc");
+
+    FILE *fp = fopen(path, "r");
+    if(!fp) return;
+
+    fseek(fp, 0, SEEK_END);
+    long fsize = ftell(fp);
+    if(fsize <= 0)
+    {
+        fclose(fp);
+        return;
+    }
+    fseek(fp, 0, SEEK_SET);
+
+    char *buffer = malloc(fsize + 1);
+    if(!buffer)
+    {
+        fclose(fp);
+        return;
+    }
+
+    size_t nread = fread(buffer, 1, fsize, fp);
+    fclose(fp);
+
+    if(nread == 0)
+    {
+        free(buffer);
+        return;
+    }
+
+    buffer[nread] = '\0';
+
+    struct source_s src;
+    src.buffer        = buffer;
+    src.buffer_size   = nread;
+    src.cursor_position = INIT_SRC_POS;
+
+    parse_and_execute(&src);
+    free(buffer);
 }

src/main.c

@@ -51,11 +51,11 @@ char *read_command(void)
 {
     char buffer[1024];
     char *pointer = NULL;
-    char pointer_length = 0;
+    size_t pointer_length = 0;
 
     while(fgets(buffer, 1024, stdin))
     {
-        int buffer_length = strlen(buffer);
+        size_t buffer_length = strlen(buffer);
 
         if(!pointer)
         {

src/prompt.c

@@ -1,35 +1,91 @@
 #include <stdio.h>
-#include "shell.h"
+#include <stdlib.h>
+#include <string.h>
 #include <unistd.h>
 #include <limits.h>
+#include <pwd.h>
+#include "shell.h"
 #include "symtab/symtab.h"
 
-#define CYN   "\x1B[36m"
-#define WHT   "\x1B[37m"
+#define GRN   "\x1B[32m"
+#define BLU   "\x1B[34m"
 #define RESET "\x1B[0m"
 
+static void get_user_name(char *buf, size_t size)
+{
+    struct passwd *pw = getpwuid(getuid());
+    if(pw && pw->pw_name)
+    {
+        strncpy(buf, pw->pw_name, size - 1);
+        buf[size - 1] = '\0';
+    }
+    else
+    {
+        buf[0] = '\0';
+    }
+}
+
+static char *display_path(char *cwd)
+{
+    char *home = getenv("HOME");
+    if(!home) return cwd;
+
+    size_t hlen = strlen(home);
+    if(strncmp(cwd, home, hlen) == 0)
+    {
+        if(cwd[hlen] == '\0' || cwd[hlen] == '/')
+        {
+            static char buf[PATH_MAX];
+            buf[0] = '~';
+            strcpy(buf + 1, cwd + hlen);
+            return buf;
+        }
+    }
+    return cwd;
+}
+
 void print_prompt1(void)
 {   
     struct symtab_entry_s *entry = get_symtab_entry("PS1");
     char user[PATH_MAX];
     char cwd[PATH_MAX];
-    cuserid(user);
-    getcwd(cwd, sizeof(cwd));
+    char hostname[256];
+
+    get_user_name(user, sizeof(user));
+    gethostname(hostname, sizeof(hostname));
+    hostname[sizeof(hostname) - 1] = '\0';
+
+    if(!getcwd(cwd, sizeof(cwd)))
+    {
+        cwd[0] = '\0';
+    }
+
+    fprintf(stderr, GRN "%s@%s" RESET ":" BLU "%s" RESET, user, hostname, display_path(cwd));
+
     if(entry && entry->val)
     {
-        fprintf(stderr,CYN "NUSH@%s>" WHT "%s" CYN "%s" RESET,user,cwd,entry->val);
+        fprintf(stderr, " " GRN "%s" RESET, entry->val);
     }
     else
     {
-        fprintf(stderr, CYN "NUSH@%s>" WHT "%s" CYN "$ " RESET,user,cwd);
+        fprintf(stderr, " " GRN "$" RESET " ");
     }
 }
 
 void print_prompt2(void)
 {
     char user[PATH_MAX];
     char cwd[PATH_MAX];
-    cuserid(user);
-    getcwd(cwd, sizeof(cwd));
-    fprintf(stderr,CYN "NUSH@%s>" WHT "%s" CYN "> " RESET,user,cwd);
+    char hostname[256];
+
+    get_user_name(user, sizeof(user));
+    gethostname(hostname, sizeof(hostname));
+    hostname[sizeof(hostname) - 1] = '\0';
+
+    if(!getcwd(cwd, sizeof(cwd)))
+    {
+        cwd[0] = '\0';
+    }
+
+    fprintf(stderr, GRN "%s@%s" RESET ":" BLU "%s" RESET " " GRN ">" RESET " ", user, hostname, display_path(cwd));
 }

src/scanner.c

@@ -18,11 +18,9 @@ struct token_s eof_token =
 
 void add_to_buf(char c)
 {
-    tok_buf[tok_bufindex++] = c;
-
-    if(tok_bufindex >= tok_bufsize)
+    if(tok_bufindex + 1 >= tok_bufsize)
     {
-        char *tmp = realloc(tok_buf, tok_bufsize*2);
+        char *tmp = realloc(tok_buf, tok_bufsize * 2);
 
         if(!tmp)
         {
@@ -33,6 +31,8 @@ void add_to_buf(char c)
         tok_buf = tmp;
         tok_bufsize *= 2;
     }
+
+    tok_buf[tok_bufindex++] = c;
 }
 
 
@@ -99,7 +99,7 @@ struct token_s *tokenize(struct source_s *src)
 
     char nc = next_character(src);
 
-    if(nc == ERRCHAR || nc == EOF)
+    if(nc == ERRCHAR || nc == SRC_EOF)
     {
         return &eof_token;
     }
@@ -138,7 +138,7 @@ struct token_s *tokenize(struct source_s *src)
             break;
         }
 
-    } while((nc = next_character(src)) != EOF);
+    } while((nc = next_character(src)) != SRC_EOF);
 
     if(tok_bufindex == 0)
     {

src/shell.h

@@ -11,6 +11,7 @@ char *read_command(void);
 int  parse_and_execute(struct source_s *src);
 
 void initsh(void);
+void load_rc_file(void);
 
 int dump(int argc, char **argv);
 

src/source.c

@@ -21,20 +21,15 @@ char next_character(struct source_s *src)
         return ERRCHAR;
     }
 
-    char c1 = 0;
     if(src->cursor_position == INIT_SRC_POS)
     {
         src->cursor_position  = -1;
     }
-    else
-    {
-        c1 = src->buffer[src->cursor_position];
-    }
 
     if(++src->cursor_position >= src->buffer_size)
     {
         src->cursor_position = src->buffer_size;
-        return EOF;
+        return SRC_EOF;
     }
 
     return src->buffer[src->cursor_position];
@@ -59,7 +54,7 @@ char peek_character(struct source_s *src)
 
     if(pos >= src->buffer_size)
     {
-        return EOF;
+        return SRC_EOF;
     }
 
     return src->buffer[pos];
@@ -75,7 +70,7 @@ void skip_white_spaces(struct source_s *src)
         return;
     }
 
-    while(((c = peek_character(src)) != EOF) && (c == ' ' || c == '\t'))
+    while(((c = peek_character(src)) != SRC_EOF) && (c == ' ' || c == '\t'))
     {
         next_character(src);
     }

src/source.h

@@ -1,7 +1,7 @@
 #ifndef SOURCE_H
 #define SOURCE_H
 
-#define EOF             (-1)
+#define SRC_EOF         (-1)
 #define ERRCHAR         ( 0)
 
 #define INIT_SRC_POS    (-2)

src/symtab/symtab.c

@@ -268,6 +268,12 @@ void symtab_entry_setval(struct symtab_entry_s *entry, char *val)
 
 void symtab_stack_add(struct symtab_s *symtab)
 {
+    if(symtab_stack.symtab_count >= MAX_SYMTAB)
+    {
+        fprintf(stderr, "fatal error: symbol table stack overflow\n");
+        exit(EXIT_FAILURE);
+    }
+
     symtab_stack.symtab_list[symtab_stack.symtab_count++] = symtab;
     symtab_stack.local_symtab = symtab;
 }