Why clone() instead of fork()?… here is a solution to the problem.
Why clone() instead of fork()?
I’m doing some work on pipelines and forks.
I have this strace output, but I’m not sure why clone is used instead of fork. Does this mean they are the same?
Trace output
enter codexecve("./forks", ["./forks"], [/* 55 vars */]) = 0
arch_prctl(ARCH_SET_FS, 0x7f2b0e498700) = 0
pipe([3, 4]) = 0
clone(Process 7304 attached
child_stack=0, flags=CLONE_CHILD_CLEARTID| CLONE_CHILD_SETTID| SIGCHLD, child_tidptr=0x7f2b0e4989d0) = 7304
[pid 7303] execve("/usr/bin/wc", ["wc", "-l"], [/* 55 vars */] <unfinished ... >
[pid 7304] execve("/bin/ls", ["ls"], [/* 55 vars */] <unfinished ... >
[pid 7303] <... execve resumed> ) = 0
[pid 7304] <... execve resumed> ) = 0
[pid 7303] arch_prctl(ARCH_SET_FS, 0x7f558acde700) = 0
[pid 7304] arch_prctl(ARCH_SET_FS, 0x7f4bef4f67c0) = 0
[pid 7304] exit_group(0) = ?
Process 7304 detached
--- SIGCHLD (Child exited) @ 0 (0) ---
21
exit_group(0)
Solution
No, fork() and clone() are not the same. However, you can think of them as functions that serve as wrappers for clone() system calls, which means that they use the same clone() system call internally to create a new process. This explains what you observe in the output of strace.
Check this and this problem; They explained the difference better than I did.