12-17-2016
Question about execl in C, replacing process's contents
I'm reading Operating Systems in Depth by Thomas W. Doeppner, and I have a question about execl. He says it's called after fork(), and that it replaces the text (code) of the current process and replaces it with the code of the new program. But that doesn't make sense to me.
Does that mean process A forks itself and its copy is process B, but process A's code is gone, and in its place is the code from process B?
OR does that mean process A forks itself and its copy is process B; process B loads a program into its text section, and now process B's text section is gone and in its place is the program it loaded?
Edit: I realize I forgot to mention the language the author uses in his examples is C
Last edited by SirSalt; 12-17-2016 at 07:08 PM..
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LEARN ABOUT REDHAT
setsid
SETSID(2) Linux Programmer's Manual SETSID(2)
NAME
setsid - creates a session and sets the process group ID
SYNOPSIS
#include <unistd.h>
pid_t setsid(void);
DESCRIPTION
setsid() creates a new session if the calling process is not a process group leader. The calling process is the leader of the new session,
the process group leader of the new process group, and has no controlling tty. The process group ID and session ID of the calling process
are set to the PID of the calling process. The calling process will be the only process in this new process group and in this new session.
RETURN VALUE
The session ID of the calling process.
ERRORS
On error, -1 will be returned. The only error which can happen is EPERM. It is returned when the process group ID of any process equals
the PID of the calling process. Thus, in particular, setsid fails if the calling process is already a process group leader.
NOTES
A process group leader is a process with process group ID equal to its PID. In order to be sure that setsid will succeed, fork and exit,
and have the child do setsid().
CONFORMING TO
POSIX, SVr4.
SEE ALSO
setpgid(2), setpgrp(2)
Linux 1.0.0 1994-08-27 SETSID(2)