Chapter 03 - Child inherits PID of parent with exec()?

I am a bit confused with this part of the chapter 03 - Creating Processes (about Fork and Exec):
Often, rather than just a fork, one follows it with an exec, where the parent process terminates, and the child process inherits the process ID of the parent.
When a process forks, the child gets a new PID. But if the child does an exec()
, it terminates the parent and inherits its PID?
What if a process creates multiple forks and each child runs the exec()
? Would that create multiple processes with the same PID?
Doesn't terminal emulators use this fork-exec pattern to run the commands that we type? Running a command foo
(that I would expect to fork and exec(foo)
) does not kill the terminal (the parent process). So, terminals don't use this pattern?
Comments
-
Hi @heitorpb ,
I'd suggest starting by reading the man pages for exec(3), execve(2), and fork(2). Fork(2) will provide you with valuable information about how it works.
I also found a couple of URLs that can be of help:
https://stackoverflow.com/questions/1653340/differences-between-fork-and-exec
https://programmerbay.com/difference-between-fork-and-exec/
Regards,
Luis.1 -
It's actually pretty simple. We are not talking about doing a fork() and then an exec*(). Note the text says:
Often, rather than just a fork, one follows it with an exec, where the parent process terminates, and the child process inherits the process ID of the parent.
Note the rather. an exec creates a new process with the same ID, one doesn't do both.
1 -
Thanks for the answers! Those man pages were very helpful.
Often, rather than just a fork, one follows it with an exec, where the parent process terminates, and the child process inherits the process ID of the parent.
I think my main source of confusion was English here (English is not my first language)... what I understood of this sentence is that if a child does an
exec()
, the parent dies and the child changes its PID to the parent PID.Is it possible to suggest to rewrite this paragraph in the course material? I would be glad to help
Just to be sure that I understood this:
- if a process does a
fork()
and it succeeds, it clones itself. The child is another process with a different PID. - if a process does an
exec()
, regardless of being a child or not, it changes its own program to a different one. This does not affect the parent of the process doing theexec
. This does not change the PID of the process, only the program running. - if a process has multiple threads, they are all terminated when one of them calls
exec
. The thread that calledexec
will survive, but with a different program.
Are those items correct?
In the case that a process has multiple threads: what happens to the other threads if the
execve
fails? Do they terminate as well?0 - if a process does a
Categories
- 8.9K All Categories
- 13 LFX Mentorship
- 66 LFX Mentorship: Linux Kernel
- 363 Linux Foundation Boot Camps
- 230 Cloud Engineer Boot Camp
- 70 Advanced Cloud Engineer Boot Camp
- 25 DevOps Engineer Boot Camp
- 5 Cloud Native Developer Boot Camp
- 845 Training Courses
- 15 LFC110 Class Forum
- 16 LFD102 Class Forum
- 102 LFD103 Class Forum
- 3 LFD121 Class Forum
- 55 LFD201 Class Forum
- 1 LFD213 Class Forum - Discontinued
- 128 LFD232 Class Forum
- 19 LFD254 Class Forum
- 431 LFD259 Class Forum
- 85 LFD272 Class Forum
- 1 LFD272-JP クラス フォーラム
- 16 LFS200 Class Forum
- 692 LFS201 Class Forum
- LFS201-JP クラス フォーラム
- 271 LFS211 Class Forum
- 50 LFS216 Class Forum
- 26 LFS241 Class Forum
- 27 LFS242 Class Forum
- 19 LFS243 Class Forum
- 6 LFS244 Class Forum
- 9 LFS250 Class Forum
- LFS250-JP クラス フォーラム
- 107 LFS253 Class Forum
- 789 LFS258 Class Forum
- 7 LFS258-JP クラス フォーラム
- 51 LFS260 Class Forum
- 78 LFS261 Class Forum
- 13 LFS262 Class Forum
- 76 LFS263 Class Forum
- 14 LFS264 Class Forum
- 10 LFS266 Class Forum
- 8 LFS267 Class Forum
- 9 LFS268 Class Forum
- 6 LFS269 Class Forum
- 180 LFS272 Class Forum
- 1 LFS272-JP クラス フォーラム
- 187 LFW211 Class Forum
- 103 LFW212 Class Forum
- 878 Hardware
- 207 Drivers
- 74 I/O Devices
- 43 Monitors
- 115 Multimedia
- 204 Networking
- 98 Printers & Scanners
- 82 Storage
- 723 Linux Distributions
- 81 Debian
- 64 Fedora
- 12 Linux Mint
- 13 Mageia
- 22 openSUSE
- 126 Red Hat Enterprise
- 33 Slackware
- 13 SUSE Enterprise
- 347 Ubuntu
- 447 Linux System Administration
- 33 Cloud Computing
- 64 Command Line/Scripting
- Github systems admin projects
- 89 Linux Security
- 73 Network Management
- 105 System Management
- 45 Web Management
- 50 Mobile Computing
- 18 Android
- 19 Development
- 1.2K New to Linux
- 1.1K Getting Started with Linux
- 499 Off Topic
- 119 Introductions
- 193 Small Talk
- 19 Study Material
- 747 Programming and Development
- 240 Kernel Development
- 473 Software Development
- 902 Software
- 247 Applications
- 178 Command Line
- 2 Compiling/Installing
- 72 Games
- 314 Installation
- 20 All In Program
- 20 All In Forum
Upcoming Training
-
August 20, 2018
Kubernetes Administration (LFS458)
-
August 20, 2018
Linux System Administration (LFS301)
-
August 27, 2018
Open Source Virtualization (LFS462)
-
August 27, 2018
Linux Kernel Debugging and Security (LFD440)