implement cat

usr/shelly/shelly_cmd.c

@@ -87,6 +87,63 @@ static errval_t shelly_cmd_cat(char * line) {
     err = shelly_write_str("(@)<_____>__(_____)____/\n\r");
     if (err_is_fail(err)) return err;
 
+
+    int res = 0;
+
+    FILE *f = fopen(line, "r");
+    if (f == NULL) {
+        return FS_ERR_OPEN;
+    }
+
+    /* obtain the file size */
+    res = fseek(f , 0 , SEEK_END);
+    if (res) {
+        return FS_ERR_INVALID_FH;
+    }
+
+    size_t filesize = ftell(f);
+    rewind(f);
+
+    char str_buf[filesize + 10];
+    snprintf(str_buf, filesize + 10, "File size is %zu\n\r", filesize);
+    err = shelly_write_str(str_buf);
+    if (err_is_fail(err)) return err;
+
+    char *file_content = calloc(filesize + 2, sizeof(char));
+    if (file_content == NULL) {
+        return LIB_ERR_MALLOC_FAIL;
+    }
+
+    size_t read = fread(file_content, 1, filesize, f);
+
+
+    snprintf(str_buf, filesize + 10, "%s\n\r", file_content);
+    err = shelly_write_str(str_buf);
+    if (err_is_fail(err)) return err;
+
+    if (read != filesize) {
+        return FS_ERR_READ;
+    }
+
+    rewind(f);
+
+    size_t nchars = 0;
+    int c;
+    do {
+        c = fgetc(f);
+        nchars++;
+    } while (c != EOF);
+
+    if (nchars < filesize) {
+        return FS_ERR_READ;
+    }
+
+    free(file_content);
+    res = fclose(f);
+    if (res) {
+        return FS_ERR_CLOSE;
+    }
+
     return SYS_ERR_OK;
 }