Fork Error Codes
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codes can’t occur on GNU systems, but they can occur using the GNU C Library on other systems. Macro: int EPERM Operation not permitted; only the owner linux kernel error codes of the file (or other resource) or processes with special privileges can perform c programming error codes the operation. Macro: int ENOENT No such file or directory. This is a “file doesn’t exist” error for ordinary
Eintr Errno
files that are referenced in contexts where they are expected to already exist. Macro: int ESRCH No process matches the specified process ID. Macro: int EINTR Interrupted function call; an asynchronous signal
Enosys Error
occurred and prevented completion of the call. When this happens, you should try the call again. You can choose to have functions resume after a signal that is handled, rather than failing with EINTR; see Interrupted Primitives. Macro: int EIO Input/output error; usually used for physical read or write errors. Macro: int ENXIO No such device or address. The system tried to use the eintr signal device represented by a file you specified, and it couldn’t find the device. This can mean that the device file was installed incorrectly, or that the physical device is missing or not correctly attached to the computer. Macro: int E2BIG Argument list too long; used when the arguments passed to a new program being executed with one of the exec functions (see Executing a File) occupy too much memory space. This condition never arises on GNU/Hurd systems. Macro: int ENOEXEC Invalid executable file format. This condition is detected by the exec functions; see Executing a File. Macro: int EBADF Bad file descriptor; for example, I/O on a descriptor that has been closed or reading from a descriptor open only for writing (or vice versa). Macro: int ECHILD There are no child processes. This error happens on operations that are supposed to manipulate child processes, when there aren’t any processes to manipulate. Macro: int EDEADLK Deadlock avoided; allocating a system resource would have resulted in a deadlock situation. The system does not guarantee that it will notice all such situations. This error means you got lucky and the system noticed; it
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Can Unix Fork Return An Error
about Stack Overflow the company Business Learn more about hiring developers or posting ads eio error in c with us Stack Overflow Questions Jobs Documentation Tags Users Badges Ask Question x Dismiss Join the Stack Overflow Community Stack Overflow posix error codes is a community of 4.7 million programmers, just like you, helping each other. Join them; it only takes a minute: Sign up What are some conditions that may cause fork() or system() calls to http://www.gnu.org/s/libc/manual/html_node/Error-Codes.html fail on Linux? up vote 5 down vote favorite 1 And how can one find out whether any of them are occuring, and leading to an error returned by fork() or system()? In other words, if fork() or system() returns with an error, what are some things in Linux that I can check to diagnose why that particular error is happening? For example: Just plain out of memory (results http://stackoverflow.com/questions/853725/what-are-some-conditions-that-may-cause-fork-or-system-calls-to-fail-on-linu in errno ENOMEM) - check memory use with 'free' etc. Not enough memory for kernel to copy page tables and other accounting information of parent process (results in errno EAGAIN) Is there a global process limit? (results in errno EAGAIN also?) Is there a per-user process limit? How can I find out what it is? ...? linux process system fork share|improve this question edited May 13 '09 at 14:39 asked May 12 '09 at 16:42 Reed Hedges 1,1941914 To clarify, when one knows that an error such as EAGAIN has occurred during fork() (errno == EAGAIN), how do you find out what specifically caused it (was it RLIMIT_NPROC? Was it an error copying page tables, or task scructure, and if so why? And how do you avoid it?) –Reed Hedges May 12 '09 at 23:44 I also asked a different, but related question about page tables in Linux: stackoverflow.com/questions/853736/… –Reed Hedges May 13 '09 at 14:40 add a comment| 2 Answers 2 active oldest votes up vote 6 down vote And how can one find out whether any of them are occuring? Check the errno value if the result (return value) is -1 From the man page on Linux: RETURN VALUE On
here for a quick overview of the site Help Center Detailed answers to any questions you might have Meta Discuss the workings and policies of this site About Us Learn more about http://stackoverflow.com/questions/5577564/what-exactly-does-fork-return Stack Overflow the company Business Learn more about hiring developers or posting ads with us Stack Overflow Questions Jobs Documentation Tags Users Badges Ask Question x Dismiss Join the Stack Overflow Community Stack Overflow is a community of 4.7 million programmers, just like you, helping each other. Join them; it only takes a minute: Sign up What exactly does fork return? up vote 11 down vote favorite 6 On error codes success, the PID of the child process is returned in the parent’s thread of execution, and a 0 is returned in the child’s thread of execution. p = fork(); I'm confused at its manual page,is p equal to 0 or PID? c linux fork share|improve this question edited Apr 7 '11 at 7:42 Oren Hizkiya 3,86511328 asked Apr 7 '11 at 7:39 compiler 1,03441931 Can someone include getpid() fork error codes in the picture? getpid() in child returns 0? –Shrinidhi Apr 7 '11 at 8:47 @Shrinidhi: So does fork(). –BoltClock♦ Apr 7 '11 at 8:50 1 It is both pid and 0. When fork is called, the program "splits" into two -- itself and its evil twin. In the original program, it is 0. In the evil twin program, it is the pid. –Stephen Chung Apr 7 '11 at 9:38 3 I would believe that a fork returns a small portion of food, but I could be wrong. ;-) –Thomas Matthews Apr 7 '11 at 20:00 add a comment| 8 Answers 8 active oldest votes up vote 28 down vote I'm not sure how the manual can be any clearer! fork() creates a new process, so you now have two identical processes. To distinguish between them, the return value of fork() differs. In the original process, you get the PID of the child process. In the child process, you get 0. So a canonical use is as follows: p = fork(); if (0 == p) { // We're the child process } else if (p > 0) { // We're the parent process } else { // We're the parent process, but child could