i want terminal

[veeco]

I have a daemon, running in background, of course. When this daemon receive a PROGRAM, it should execute the PROGRAM. My question is:

How can i open a new terminal from my daemon and run that PROGRAM in the terminal so that user can interact with the PROGRAM?

I create my daemon with C.
Thanks.

[binaryDigit]

EXEC(3) Unix Programmer's Manual EXEC(3)

NAME
execl, execlp, execle, exect, execv, execvp -- execute a file

SYNOPSIS
#include <unistd.h>

extern char **environ;

int
execl(const char *path, const char *arg)
int
execlp(const char *file, const char *arg)

int
execle(const char *path, const char *arg, char *const envp[])

int
exect(const char *path, char *const argv[], char *const envp[])

int
execv(const char *path, char *const argv[])

int
execvp(const char *file, char *const argv[])


DESCRIPTION
The exec family of functions replaces the current process image with a new process image. The functions described in this manual page are front-ends for the function execve(2). (See the manual page for execve() for detailed information about the replacement of the current process.)
The initial argument for these functions is the pathname of a file which is to be executed.

The "constchar *arg" and subsequent ellipses in the execl(), execlp(), and execle() functions can be thought of as arg0, arg1, \&..., argn. Together they describe a list of one or more pointers to null-terminated strings that represent the argument list available to the executed program. The first argument, by convention, should point to the file name associated with the file being executed. The list of arguments must be terminated by a NULL pointer.

The exect(), execv(), and execvp() functions provide an array of pointers to null-terminated strings that represent the argument list available to the new program. The first argument, by convention, should point to the file name associated with the file begin executed. The array of pointers mustmust be terminated by a NULL pointer.

The execle() and exect() functions also specify the environment of the executed process by following the NULL pointer that terminates the list of arguments in the parameter list or the pointer to the argv array with an additional parameter. This additional parameter is an array of pointers to null-terminated strings and must be terminated by a NULL pointer. The other functions take the environment for the new process image from the external variable environ in the current process.

Some of these functions have special semantics.

The functions execlp() and execvp() will duplicate the actions of the shell in searching for an executable file if the specified file name does not contain a slash ``Li''/ character. The search path is the path specified in the environment by ``Ev''PATH variable. If this variable isn't specified, the default path ``Ev''/bin:/usr/bin: is used. In addition, certain errors are treated specially.

If permission is denied for a file (the attempted execve() returned EACCES) , these functions will continue searching the rest of the search path. If no other file is found, however, they will return with the global variable errno set to EACCES.

If the header of a file isn't recognized (the attempted execve() returned ENOEXEC) , these functions will execute the shell with the path of the file as its first argument. (If this attempt fails, no further searching is done.)

If the file is currently busy (the attempted execve() returned ETXTBUSY) , these functions will sleep for several seconds, periodically re-attempting to execute the file.

The function exect() executes a file with the program tracing facilities enabled (see ptrace(2)) .


RETURN VALUES
If any of the exec() functions returns, an error will have occurred. The return value is \-1, and the global variable errno will be set to indicate the error.

FILES
[/bin/sh]
The shell.

ERRORS
Execl(), execle(), execlp() and execvp() may fail and set errno for any of the errors specified for the library functions execve(2) and malloc(3).
Exect() and execv() may fail and set errno for any of the errors specified for the library function execve(2).


SEE ALSO
sh(1), execve(2), fork(2), trace(2), environ(7), ptrace(2), environ(7),

COMPATIBILITY
Historically, the default path for the execlp() and execvp() functions was ``Pa'':/bin:/usr/bin . This was changed to place the current directory last to enhance system security.
The behavior of execlp() and execvp() when errors occur while attempting to execute the file is historic practice, but has not traditionally been documented and is not specified by the POSIX standard.

Traditionally, the functions execlp() and execvp() ignored all errors except for the ones described above and ENOMEM and E2BIG, upon which they returned. They now return if any error other than the ones described above occurs.


STANDARDS
Execl(), execv(), execle(), execlp() and execvp() conform to IEEE STD1003.1-88 (``POSIX'').

[veeco]

Well, i can run a program from my DAEMON using exec-family. But now the problem is the output(input as well). I can see the output if only the terminal that start the DAEMON still running. Normally the terminal will be closed after the DAEMON started. When this is the case, where is output:confused:
The output of ps command before and after the terminal close are:

TTY TIME CMD
pts/2 00:00:00 daemon2 //before
? 00:00:00 daemon2 //after

See, ? under TTY, daemon2 was not connected to any terminal.

So, what's the solution to get daemon2 connected to a new terminal before it run any program? Any idea?

Thanks.

[bwkaz]

You don't, unless you can get access to the source of daemon2 -- and even then, it requires intimate knowledge of the way TTYs work in Linux, knowledge I don't have.

Just about all that normal daemons can do once their terminal (or console) is disconnected, is syslog() stuff. It might be possible to reconnect, but I don't know how.

Would syslog() work for you?

[veeco]

Thanks for the info. I'll check on it and see what syslog() can do for me.
I found a chapter about terminal in a book, talking termios structure, terminfo and it came with examples that show 'writing to' and 'reading from' terminal. But the examples shown are dealing directly with terminal, in my case it's indirectly (not my daemon talking to terminal, the program run by daemon instead). Do you think this will help in some way?

What do you mean "you can get access to the SOURCE of daemon2"?
Thanks.

[bwkaz]

Did you write daemon2 yourself? Or are you running someone else's program?

If it's someone else's, is it released under either the GPL or some other free software license, so that you have access to the source code for it?

[veeco]

Oh yes, I write it myself.
I just found an alternative to solve my problem:

gnome-terminal -e COMMAND

It open a new terminal and run COMMAND. Another alternative i'm thinking of is using a shell script, but i haven't try it yet.
Thanks.