Initial Commit

src/msh.c

@@ -0,0 +1,135 @@
+#define _GNU_SOURCE
+
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include <unistd.h>
+#include <sys/wait.h>
+#include <sys/utsname.h>
+#include <errno.h>
+
+
+#define ESC \x1B
+
+
+const int LINESIZE = 512;
+
+int cd(int argc, char** argv) {
+    if (argc != 1) {
+        fprintf(stderr, "Usage: cd <directory>\n");
+        return 1;
+    }
+
+    return chdir(argv[0]);
+}
+
+
+void pretty_path_home(char** path) {
+    char* home = secure_getenv("HOME");
+    int home_len = strlen(home);
+
+    if (strncmp(home, *path, home_len) == 0) {
+        (*path)[home_len-1] = '~';
+        *path = *path + (home_len - 1);
+    }
+}
+
+
+int main(int argc, char** argv) {
+    char*  tokens[LINESIZE] = {};
+    char** args;
+    char  line[LINESIZE] = {};
+    char* tokenwork;
+    char* token;
+    char* newline;
+    int ntokens = 0;
+
+    int i;
+    int result;
+
+    int pid;
+    int laststatus = 0;
+
+    int wstatus;
+    char pwd[LINESIZE] = {};
+    char* pwd_disp;
+
+    char* user;
+    char* host;
+
+    struct utsname uts = {};
+
+    user = secure_getenv("USER");
+
+    result = uname(&uts);
+    if (result != 0) {
+        fprintf(stderr, "Error: %s\n", strerror(errno));
+        return errno;
+    }
+
+    host = uts.nodename;
+
+    while(1) {
+        getcwd(pwd, LINESIZE - 1);
+        pwd_disp = pwd;
+
+        pretty_path_home(&pwd_disp);
+
+        if (laststatus != 0) {
+            fprintf(stdout, "❌");
+        }
+        fprintf(stdout, "%s@%s %s$ ", user, host, pwd_disp);
+        char* fgets_res = fgets(line, LINESIZE, stdin);
+
+        if (fgets_res == NULL) {
+            printf("^D\n");
+            return 0;
+        }
+
+        newline = strrchr(line, '\n');
+        if (newline != NULL) {
+            newline[0] = 0;
+        }
+
+        for (tokenwork = line, i = 0; ; tokenwork = NULL, i++) {
+            token = strtok(tokenwork, " \t");
+            if (token == NULL) {
+                break;
+            }
+
+            tokens[i] = token;
+        }
+
+        ntokens = i;
+        tokens[ntokens] = NULL;
+        args = &tokens[1];
+
+        if (ntokens == 0) {
+            continue;
+        }
+
+        // Shell builtins
+        if (strcmp("exit", tokens[0]) == 0) {
+            printf("Goodbye!\n");
+            return 0;
+        }
+
+        if (strcmp("cd", tokens[0]) == 0) {
+            laststatus = cd(ntokens - 1, args);
+            continue;
+        }
+
+        // Execute command
+        pid = fork();
+
+        if(pid == 0) {
+            return execvpe(tokens[0], tokens, NULL);
+        } else {
+            waitpid(pid, &wstatus, 0);
+
+            laststatus = WEXITSTATUS(wstatus);
+        }
+
+    }
+}
+