fix: do not read ahead in STDIN

The Open Group Base Specifications Issue 8 IEEE Std 1003.1-2024 sh — shell, the
standard command language interpreter says:

> When the shell is using standard input and it invokes a command that also uses
> standard input, the shell shall ensure that the standard input file pointer
> points directly after the command it has read when the command begins
> execution. It shall not read ahead in such a manner that any characters
> intended to be read by the invoked command are consumed by the shell (whether
> interpreted by the shell or not) or that characters that are not read by the
> invoked command are not seen by the shell.

We used the default BUFFER_SIZE for get_next_line of 1024, which caused us to
read ahead farther than was allowed by the Open Group Base Specification.

Setting BUFFER_SIZE=1 ensures that we don't read too far ahead, since
get_next_line will always immediatly stop once a newline is found.

This is for me the simplest way to solve this issue.

Makefile

@@ -100,6 +100,7 @@ all: $(NAME)
 $(NAME): $(minishell_objs) $(LIBFT)
 	$(CC) $(CFLAGS) -o $@ $(minishell_objs) $(LINCLUDE) $(LDLIBS)
 
+$(LIBFT): CFLAGS+=-DBUFFER_SIZE=1
 $(LIBFT):
 	+$(MAKE) -C $(LIBFTDIR)
 

src/executing/simple_cmd/simple_cmd_execute.c

@@ -6,7 +6,7 @@
 /*   By: khais <marvin@42.fr>                       +#+  +:+       +#+        */
 /*                                                +#+#+#+#+#+   +#+           */
 /*   Created: 2025/03/27 16:21:56 by khais             #+#    #+#             */
-/*   Updated: 2025/04/01 16:37:31 by khais            ###   ########.fr       */
+/*   Updated: 2025/04/01 18:08:02 by khais            ###   ########.fr       */
 /*                                                                            */
 /* ************************************************************************** */
 
@@ -17,6 +17,8 @@
 #include "../../env/env_convert.h"
 #include <unistd.h>
 #include <sys/wait.h>
+#include <stdio.h>
+#include "../../subst/path_split.h"
 
 static char	**argv_from_wordlist(t_wordlist *wordlist)
 {
@@ -39,6 +41,24 @@ static void	command_not_found(t_simple_cmd *cmd)
 		cmd->words->word->word);
 }
 
+static void	ft_execve(char *exe, char **argv, char **envp)
+{
+	execve(exe, argv, envp);
+	ft_dprintf(STDERR_FILENO, "minishell: %s: ", argv[0]);
+	perror(NULL);
+	free(exe);
+	path_split_destroy(argv);
+	path_split_destroy(envp);
+}
+
+static void	execute_subprocess(char *exe, t_simple_cmd *cmd, t_minishell *app)
+{
+	ft_execve(exe, argv_from_wordlist(cmd->words), envp_from_env(app->env));
+	simple_cmd_destroy(cmd);
+	env_destroy(app->env);
+	exit(127);
+}
+
 void	simple_cmd_execute(t_simple_cmd *cmd, t_minishell *app)
 {
 	char	*exe;
@@ -56,7 +76,7 @@ void	simple_cmd_execute(t_simple_cmd *cmd, t_minishell *app)
 	}
 	pid = fork();
 	if (pid == 0)
-		execve(exe, argv_from_wordlist(cmd->words), envp_from_env(app->env));
+		execute_subprocess(exe, cmd, app);
 	free(exe);
 	waitpid(pid, NULL, 0);
 	return ;

src/subst/simple_filename_exp.c

@@ -6,7 +6,7 @@
 /*   By: khais <marvin@42.fr>                       +#+  +:+       +#+        */
 /*                                                +#+#+#+#+#+   +#+           */
 /*   Created: 2025/03/02 13:40:10 by jguelen           #+#    #+#             */
-/*   Updated: 2025/03/27 18:39:23 by khais            ###   ########.fr       */
+/*   Updated: 2025/04/01 18:38:35 by khais            ###   ########.fr       */
 /*                                                                            */
 /* ************************************************************************** */
 
@@ -77,8 +77,6 @@ static char	*select_path(char *filepath, char **oldpath, char **path,
 		else
 			return (free(*oldpath), path_split_destroy(path), filepath);
 	}
-	if (*oldpath != filepath)
-		free(filepath);
 	return (NULL);
 }
 

test.sh

@@ -335,6 +335,13 @@ status=1
 hello=hi
 EOF
 
+when_run <<EOF "empty command is not found"
+""
+EOF
+expecting <<EOF
+minishell: : command not found
+EOF
+
 when_run <<EOF "quoted parentheses are not operators"
 echo unclosed '('
 EOF