An example Analysis of the use of fork function in Linux

In this article Xiaobian for you to introduce in detail the "Linux fork function use case analysis", the content is detailed, the steps are clear, the details are handled properly, I hope this "Linux fork function use case analysis" article can help you solve your doubts, the following follow the editor's ideas slowly in-depth, together to learn new knowledge.

A process, including code, data, and resources assigned to the process. The fork () function creates a process that is almost identical to the original process through a system call, that is, two processes can do exactly the same thing, but if the initial parameters or the variables passed in are different, the two processes can also do different things.

After a process calls the fork () function, the system first allocates resources to the new process, such as the space to store data and code. Then copy all the values of the original process to the new process, except for the few values that are different from those of the original process. It's the equivalent of cloning yourself.

Example: / * > File Name: fork_test.c > Author: > Mail: > Created Time: 09:29:05 on Monday, June 6, 2016 * * * / # include # include int main () {pid_t fpid / / fpid represents the value returned by the fork function int count=0; fpid=fork (); if (fpid printf ("error in fork!"); else if (fpid= = 0) {printf ("child process | process id=% d | fpid=% d | parentid =% d\ n", getpid (), fpid,getppid ()); count++ } else {printf ("parent process | process id=% d | fpid =% d | parentid =% d\ n", getpid (), fpid,getppid ()); count++;} printf ("Statistical result is:% d\ n", count); getchar (); return 0;} 123456789101112131415161718192021222324252627

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There may be two reasons for fork errors: 1) the current number of processes has reached the limit specified by the system, and the value of errno is set to EAGAIN. 2) the system is out of memory, so the value of errno is set to ENOMEM.

Second, fork advanced knowledge

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Example

# include # include int main (void) {int ibido; printf ("I son/pa ppid pid fpid\ n"); / / ppid refers to the parent process of the current process pid / / pid refers to the pid of the current process, and / / fpid refers to the value for returned by the fork to the current process. Iif (fpid==0) printf ("iForce% d | child ppid=%4d | pid=%4d | fpid=%4d\ n", iGramage getppid (), getpid (), fpid); else printf ("iQuest% d | parent ppid=%4d | pid=%4d | fpid=%4d\ n", iGramage getppid (), getpid (), fpid);} getchar (); return 0;} 1234567891011121314151617181920

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Running result

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View the process

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Analysis.

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