From fb322edd72bebddee1a9828baec2f8bc83666ddf Mon Sep 17 00:00:00 2001
From: scratko <m@scratko.xyz>
Date: Sat, 25 May 2024 21:36:07 +0300
Subject: Shell-II release

Implementation of launching external programs via fork().
Running cd as a change to the current process directory (chdir).
Ability to change to user's home directory (cd without arguments).
---
 shell.c | 86 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 83 insertions(+), 3 deletions(-)

(limited to 'shell.c')

diff --git a/shell.c b/shell.c
index f635c12..a1b5b29 100644
--- a/shell.c
+++ b/shell.c
@@ -2,6 +2,9 @@
 #include "dynamic_array.h"
 #include <stdio.h>
 #include <stdlib.h>
+#include <unistd.h>
+#include <string.h>
+#include <sys/wait.h>
 
 enum modes { word_separation, whole_word };
 enum {
@@ -57,7 +60,8 @@ static int is_double_quotes_pair(struct param_type params)
 
 static int check_separation(int ch, struct param_type params)
 {
-    return (ch == whitespace || ch == tab) && params.is_word && !params.escape_sequences;
+    return (ch == whitespace || ch == tab) && params.is_word &&
+            !params.escape_sequences;
 }
 
 static int ignore_spaces(int ch, struct param_type params)
@@ -87,6 +91,7 @@ static void add_word(struct queue *word_chain,
     params->is_word = 0;
 }
 
+#if 0
 static void print_word(char *word)
 {
     putchar('[');
@@ -101,6 +106,77 @@ static void print_line(const struct queue *word_chain)
 {
     queue_processing(word_chain, print_word);
 }
+#endif
+
+static char** create_cmdline(const struct queue *word_chain,
+                                   int word_counter)
+{
+    char **cmdline = malloc((word_counter + 1) * sizeof(char*));
+    queue_copy_words_to_args(word_chain, cmdline);
+    return cmdline;
+}
+
+static int check_cd(const char *arg)
+{
+    return !strcmp(arg, "cd");
+}
+
+static void change_directory(char **cmdline)
+{
+    int result;
+    char *first_arg = cmdline[1];
+    char *path = NULL;
+    /* change to user home directory */
+    if(first_arg == NULL) {
+        path = getenv("HOME");
+        if(!path) {
+            perror("I don't know where's your home...");
+            return;
+        }
+    } else {
+        if(cmdline[2]) {
+            perror("cd: too many arguments");
+            return;
+        }
+        path = first_arg;
+    }
+    result = chdir(path);
+    if(result == -1)
+        perror(path);
+}
+
+static void clean_up_memory(struct queue *word_chain, char **cmdline)
+{
+    queue_clear(word_chain);
+    free(cmdline);
+}
+
+static void run_external_program(struct queue *word_chain)
+{
+    int pid, result;
+    char **cmdline = create_cmdline(word_chain,
+                                    queue_get_word_count(word_chain));
+    if(check_cd(cmdline[0])) {
+        change_directory(cmdline);
+        clean_up_memory(word_chain, cmdline);
+    }
+    else {
+        pid = fork();
+        if(pid == -1) {
+            perror("fork error");
+            exit(1);
+        }
+        /* child process  */
+        if(pid == 0) {
+            execvp(cmdline[0], cmdline);
+            perror(cmdline[0]);
+            exit(1);
+        }
+        /* parent process */
+        wait(&result);
+        clean_up_memory(word_chain, cmdline);
+    }
+}
 
 static void new_line_processing(struct param_type *params,
                                 enum modes *current_mode,
@@ -119,14 +195,18 @@ static void new_line_processing(struct param_type *params,
             dynarr_push_back(tmp_word, '\0');
         add_word(word_chain, tmp_word, params);
     }
+    run_external_program(word_chain);
+#if 0
     print_line(word_chain);
+#endif
     prepare_new_line(params, current_mode, word_chain, tmp_word);
     show_invitation();
 }
 
 static int is_empty_word(int ch, struct param_type params)
 {
-    return (ch == whitespace || ch == tab) && !params.is_word && params.empty_word_flag;
+    return (ch == whitespace || ch == tab) && !params.is_word &&
+            params.empty_word_flag;
 }
 
 static void word_separation_processing(int ch, struct param_type *params,
@@ -198,6 +278,7 @@ static void whole_word_processing(int ch, struct param_type *params,
     if(escape_double_quotes_or_backslash(ch, *params)) {
         dynarr_push_back(tmp_word, ch);
         params->escape_sequences = 0;
+        params->is_word = 1;
         return;
     }
     if(start_escape_sequence(ch, *params)) {
@@ -235,7 +316,6 @@ int main()
                                   &tmp_word);
     }
     putchar(new_line);
-    queue_clear(&word_chain);
     dynarr_clear(&tmp_word);
     return 0;
 }
-- 
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