External Commands

This module provides functions to execute external commands. More...

Functions
int	fork_detach_execvp (char **eargv)
	Fork, set new session ID, close files, and execute detached command.
int	fork_exec (char **argv)
	Fork and exec a command.
int	full_screen_fork_exec (char **argv)
	Execute a command in full screen mode.
int	full_screen_shell (char *shellCmdPtr)
	Execute a shell command in full screen mode.
int	shell (char *shellCmdPtr)
	Execute a shell command.

Detailed Description

This module provides functions to execute external commands.

Handles terminal settings, signal handling, and error reporting to ensure a smooth user experience when executing commands from within the application. The main functions include full_screen_fork_exec, full_screen_shell, and fork_exec, which manage the execution of commands while maintaining the integrity of the application's user interface.

Function Documentation

fork_detach_execvp()

int fork_detach_execvp

(

char **

eargv

)

Fork, set new session ID, close files, and execute detached command.

Fork, detach, and exec a command.

Parameters

eargv

- array of arguments for the command to execute

Returns

EXIT_SUCCESS on success, EXIT_FAILURE on failure

Sets the new session ID. Redirects standard file descriptors to /dev/null. Closes all open file descriptors. Executes the command using execvp. Exits with failure if any step fails.

Note

Tested 2026-06-05 on Linux - appears to be functioning properly

Parameters

eargv

- array of arguments for the command to execute

Returns

0 on success, or exits on failure

Forks a new process, detaches it from the terminal, and executes the specified command using execvp. Closes standard input, output, and error file descriptors in the child process. Redirects standard input, output, and error to /dev/null in the child process. Closes all other file descriptors in the child process. Sets the session ID for the child process to detach it from the terminal. Restores curses mode and signal handling in the parent process after forking. Restores window states in the parent process after forking.

Definition at line 29 of file detach.c.

                                     {
    pid_t pid = fork();
 
    if (pid < 0) {
        fprintf(stderr, "First fork failed: %s\n", strerror(errno));
        exit(EXIT_FAILURE);
    }
    if (pid == 0) {
        if (setsid() < 0) {
            fprintf(stderr, "Set session ID failed: %s\n", strerror(errno));
            exit(EXIT_FAILURE);
        }
        close(STDIN_FILENO);
        close(STDOUT_FILENO);
        close(STDERR_FILENO);
        int dev_null = open("/dev/null", O_RDWR);
        if (dev_null != -1) {
            dup2(dev_null, STDIN_FILENO);
            dup2(dev_null, STDOUT_FILENO);
            dup2(dev_null, STDERR_FILENO);
            if (dev_null > 2) {
                close(dev_null);
            }
        }
        long max_fd = sysconf(_SC_OPEN_MAX);
        for (long fd = 3; fd < max_fd; fd++)
            close(fd);
        execvp(eargv[0], eargv);
        perror("execvp failed");
        exit(EXIT_FAILURE);
    }
    return 0;
}

Referenced by main(), and menu_cmd_processor().

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fork_exec()

int fork_exec

(

char **

argv

)

Fork and exec a command.

Parameters

argv	- array of arguments for the command to execute

Returns

the return code from the executed command, or -1 on error

Captures and restores terminal settings around the fork and exec. Sets signal handlers to default in the child process. Waits for the child process to complete in the parent process. Handles errors from fork and execvp, and reports child exit status. Restores curses mode and keypad settings after execution. Restores window states after execution. Uses a temporary string buffer tmp_str for error messages. Uses Perror for error reporting. Uses sig_dfl_mode and sig_prog_mode for signal handling. Uses capture_curses_tioctl and restore_curses_tioctl for terminal settings. Uses restore_shell_tioctl for shell terminal settings. Uses waitpid to wait for the child process. Uses WIFEXITED, WEXITSTATUS, WIFSIGNALED, and WTERMSIG to interpret child status. Uses keypad to manage keypad mode in curses. Uses restore_wins to restore window states. Uses errno for error codes. Uses pid_t for process IDs. Uses standard file descriptors STDIN_FILENO, STDOUT_FILENO, STDERR_FILENO. Uses execvp for executing the command. Uses fork for creating a new process. Uses ssnprintf for formatting error messages. Uses switch-case for handling fork results. Uses default shell if SHELL environment variable is not set.

Definition at line 126 of file exec.c.

                           {
    char tmp_str[MAXLEN];
    pid_t pid;
    int status;
    int rc;
 
    if (argv[0] == 0) {
        Perror("fork_exec: missing argument for execvp");
        return (-1);
    }
    capture_curses_tioctl();
    curs_set(1);
    sig_dfl_mode();
    stdio_names(stdio_names_str, "exec.c:139");
    endwin();
    stdio_names(stdio_names_str, "exec.c:141");
    tmp_str[0] = '\0';
    pid = fork();
    if (pid < 0) {
        sig_prog_mode();
        keypad(stdscr, true);
        ssnprintf(tmp_str, sizeof(tmp_str), "fork failed: %s, errno: %d",
                  argv[0], errno);
        Perror(tmp_str);
        return (-1);
    } else if (pid == 0) {
        restore_shell_tioctl();
        sig_dfl_mode();
        execvp(argv[0], argv);
        fprintf(stderr, "execvp failed: %s, errno: %d\n", argv[0], errno);
        exit(EXIT_FAILURE);
    }
    waitpid(pid, &status, 0);
    if (WIFEXITED(status)) {
        rc = WEXITSTATUS(status);
    } else if (WIFSIGNALED(status)) {
        ssnprintf(tmp_str, sizeof(tmp_str), "Child process terminated by signal: %d",
                  WTERMSIG(status));
        Perror(tmp_str);
        rc = -1;
    } else {
        ssnprintf(tmp_str, sizeof(tmp_str), "Child process terminated abnormally");
        Perror(tmp_str);
        rc = -1;
    }
    reset_prog_mode();
    restore_wins();
    return (rc);
}

References capture_curses_tioctl(), Perror(), restore_shell_tioctl(), restore_wins(), sig_dfl_mode(), sig_prog_mode(), ssnprintf(), stdio_names(), and stdio_names_str.

Referenced by full_screen_fork_exec(), and shell().

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full_screen_fork_exec()

int full_screen_fork_exec

(

char **

argv

)

Execute a command in full screen mode.

Parameters

argv	- array of arguments for the command to execute

Returns

the return code from the executed command

Clear the screen, move the cursor to the bottom, and update the screen before executing the command. After the command completes, clear the screen, move the cursor to the top, update the screen, and restore the windows.

Definition at line 46 of file exec.c.

                                       {
    int rc;
 
    fflush(stderr);
    wmove(stdscr, LINES - 1, 0);
    rc = fork_exec(argv);
    return (rc);
}

References fork_exec().

Referenced by menu_cmd_processor().

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full_screen_shell()

int full_screen_shell

(

char *

shellCmdPtr

)

Execute a shell command in full screen mode.

Parameters

shellCmdPtr

- pointer to the shell command string

Returns

the return code from the executed shell command

Clear the screen, move the cursor to the top, and update the screen before executing the shell command. After the command completes, restore the windows.

Definition at line 62 of file exec.c.

                                         {
    int rc;
 
    fflush(stderr);
    werase(stdscr);
    wmove(stdscr, 0, 0);
    rc = shell(shellCmdPtr);
    restore_wins();
    return (rc);
}

References restore_wins(), and shell().

Referenced by menu_cmd_processor(), and view_cmd_processor().

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shell()

int shell

(

char *

shellCmdPtr

)

Execute a shell command.

Parameters

shellCmdPtr

- pointer to the shell command string

Returns

the return code from the executed shell command

Executes the command string using the user's shell. If the SHELL environment variable is not set, use /bin/sh.

Definition at line 78 of file exec.c.

                             {
    int Eargc;
    char *Eargv[MAXARGS];
    char *shellPtr;
    int rc;
 
    Eargc = 0;
    shellPtr = getenv("SHELL");
    if (shellPtr == nullptr || *shellPtr == '\0')
        shellPtr = DEFAULTSHELL;
    Eargv[Eargc++] = strdup(shellPtr);
    Eargv[Eargc++] = "-c";
    Eargv[Eargc++] = shellCmdPtr;
    Eargv[Eargc++] = nullptr;
    rc = fork_exec(Eargv);
    free(Eargv[0]);
    return (rc);
}

References fork_exec().

Referenced by form_exec_cmd(), full_screen_shell(), lp(), and view_cmd_processor().

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