企业官网建设流程全解析

仿制手机网站教程,简网app工场官网是不是不可以用了,网站建设需要注意什么哪些,网站建设程序员提成进程创建 fork函数 fork函数是Linux系统提供的接口#xff0c;其功能就是创建子进程。 既调用fork函数#xff0c;系统就自动为我们创建好了子进程。 代码语言#xff1a;javascript AI代码解释 #includeunistd.h pid_t fork();其中pid_t是Linux中的数据类型其功能就是创建子进程。既调用fork函数系统就自动为我们创建好了子进程。代码语言javascriptAI代码解释#includeunistd.h pid_t fork(); 其中pid_t是Linux中的数据类型相当于int即为整型fork的返回值有两个对于父进程返回子进程的pid对于子进程返回0。代码语言javascriptAI代码解释#include stdio.h #include unistd.h int main() { pid_t pid fork(); if(pid0) { printf(创建失败); } else if(pid 0) { //子进程 printf(我是一个子进程%d,这是我的父进程%d\n,getpid(),getppid()); } else if(pid 0) { printf(我是一个父进程%d,这是我的父进程%d\n,getpid(),getppid()); } }对于fork原理的详细介绍可参考【Linux】初见进程概念-CSDN博客中的第四节“如何创建进程”这里面有超级详细的介绍fork的用法一个父进程希望复制自己使父子进程同时执行不同的代码段。e.g. 父进程等待客户端响应生成子进程处理请求。一个进程想要执行多个不同的代码。e.g. 生成子进程调用exec函数。fork失败原因系统中的进程太多了用户的进程数量超过了限制进程终止进程终止的本质就是进程结束系统释放资源释放进程申请的相关数据结构和对应的代码与数据进程退出的场景1.代码运行完毕结果正确退出码为02.代码运行完毕结果不正确退出码为非03.代码异常终止进程接收到型号终止退出码无意义进程退出方法正常退出1.从main函数返回2.调用exit3._exit异常退出信号终止退出码退出码可以告诉我们进程终止时的状态0代表执行成功非0则代表不成功。非0的退出码中一个值对应一个错误原因。可以使用strerror函数获取退出码对应的信息。代码语言javascriptAI代码解释#include stdio.h #includestring.h int main() { for(int i0;i200;i) { printf(%d - %s\n,i,strerror(i)); } }代码语言javascriptAI代码解释0 - Success 1 - Operation not permitted 2 - No such file or directory 3 - No such process 4 - Interrupted system call 5 - Input/output error 6 - No such device or address 7 - Argument list too long 8 - Exec format error 9 - Bad file descriptor 10 - No child processes 11 - Resource temporarily unavailable 12 - Cannot allocate memory 13 - Permission denied 14 - Bad address 15 - Block device required 16 - Device or resource busy 17 - File exists 18 - Invalid cross-device link 19 - No such device 20 - Not a directory 21 - Is a directory 22 - Invalid argument 23 - Too many open files in system 24 - Too many open files 25 - Inappropriate ioctl for device 26 - Text file busy 27 - File too large 28 - No space left on device 29 - Illegal seek 30 - Read-only file system 31 - Too many links 32 - Broken pipe 33 - Numerical argument out of domain 34 - Numerical result out of range 35 - Resource deadlock avoided 36 - File name too long 37 - No locks available 38 - Function not implemented 39 - Directory not empty 40 - Too many levels of symbolic links 41 - Unknown error 41 42 - No message of desired type 43 - Identifier removed 44 - Channel number out of range 45 - Level 2 not synchronized 46 - Level 3 halted 47 - Level 3 reset 48 - Link number out of range 49 - Protocol driver not attached 50 - No CSI structure available 51 - Level 2 halted 52 - Invalid exchange 53 - Invalid request descriptor 54 - Exchange full 55 - No anode 56 - Invalid request code 57 - Invalid slot 58 - Unknown error 58 59 - Bad font file format 60 - Device not a stream 61 - No data available 62 - Timer expired 63 - Out of streams resources 64 - Machine is not on the network 65 - Package not installed 66 - Object is remote 67 - Link has been severed 68 - Advertise error 69 - Srmount error 70 - Communication error on send 71 - Protocol error 72 - Multihop attempted 73 - RFS specific error 74 - Bad message 75 - Value too large for defined data type 76 - Name not unique on network 77 - File descriptor in bad state 78 - Remote address changed 79 - Can not access a needed shared library 80 - Accessing a corrupted shared library 81 - .lib section in a.out corrupted 82 - Attempting to link in too many shared libraries 83 - Cannot exec a shared library directly 84 - Invalid or incomplete multibyte or wide character 85 - Interrupted system call should be restarted 86 - Streams pipe error 87 - Too many users 88 - Socket operation on non-socket 89 - Destination address required 90 - Message too long 91 - Protocol wrong type for socket 92 - Protocol not available 93 - Protocol not supported 94 - Socket type not supported 95 - Operation not supported 96 - Protocol family not supported 97 - Address family not supported by protocol 98 - Address already in use 99 - Cannot assign requested address 100 - Network is down 101 - Network is unreachable 102 - Network dropped connection on reset 103 - Software caused connection abort 104 - Connection reset by peer 105 - No buffer space available 106 - Transport endpoint is already connected 107 - Transport endpoint is not connected 108 - Cannot send after transport endpoint shutdown 109 - Too many references: cannot splice 110 - Connection timed out 111 - Connection refused 112 - Host is down 113 - No route to host 114 - Operation already in progress 115 - Operation now in progress 116 - Stale file handle 117 - Structure needs cleaning 118 - Not a XENIX named type file 119 - No XENIX semaphores available 120 - Is a named type file 121 - Remote I/O error 122 - Disk quota exceeded 123 - No medium found 124 - Wrong medium type 125 - Operation canceled 126 - Required key not available 127 - Key has expired 128 - Key has been revoked 129 - Key was rejected by service 130 - Owner died 131 - State not recoverable 132 - Operation not possible due to RF-kill 133 - Memory page has hardware error使用echo $?可以打印出最近一个程序的退出码。退出码是进程的性质之一所以退出码会保存到进程的PCB中。_exit函数代码语言javascriptAI代码解释#includeunistd.h void _exit(int status); 在任何地方调用_exit函数都会让当前进程结束 并以给定的值作为退出码退出exit函数代码语言javascriptAI代码解释#includeunistd.h void exit(int status); 与_exit函数功能类似 都是以指定的退出码退出当前进程区别_exit函数系统调用而exit是C语言提供。使用exit函数退出时会进行缓冲区的刷新。反之_exit则不会。举个例子说明程序结束刷新缓冲区信息打印在屏幕上反之没有信息打印。感兴趣的朋友可以看看这篇文章这里有详细的缓冲区刷新介绍【Linux】LInux下第一个程序进度条-CSDN博客代码语言javascriptAI代码解释#include stdio.h #includestring.h #includeunistd.h int main() { printf(yuzuriha); sleep(1); exit(0); }代码语言javascriptAI代码解释#include stdio.h #includestring.h #includeunistd.h int main() { printf(yuzuriha); sleep(1); _exit(0); }进程等待进程等待的必要性1.之前我们讲过子进程的退出后子进程回进入僵尸状态必须要被父进程回收才行。若子进程一直没有被父进程回收就会一直处于僵尸状态进而造成内存泄漏。2.进程被创造出来执行任务结果如何是成功、失败还是异常这是父进程要得知的必要信息。所以回收子进程是必要的父进程通过进程等待的方式回收子进程进程资源、获取子进程的退出信息。进程等待的方法wait方法代码语言javascriptAI代码解释#includesys/types.h #includesys/wait.h pid_t wait(int* status); 返回值等待成功返回对应的子进程pid失败则返回-1 参数status为输出型参数可以获取子进程的退出码 若不需要可以传NULL忽略这个参数waitpid函数代码语言javascriptAI代码解释#includesys/types.h #includesys/wait.h pid_ t waitpid(pid_t pid, int *status, int options);下面详细介绍一下每一个参数pid_t pid参数pid-1表示可以等待任意一个子进程。参数pid0表示只能等待当前这个进程的子进程。status如上面所讲status是一个输出型参数由操作系统填充我们可以通过status获取进程状态。status并不是一个简单的整型细节如下1.status是一个低16位有效的int通过位划分存储子进程的信息 2.正常终止的情况下低7位全为015~8存放退出码。 获取退出码WEXITSTATUS(status)3.非正常退出退出码无意义第7位存放标志6~0存放信号编号判断一个进程是否位正常退出WIFEXITED(status)正常为真。optionsoptions的默认值是0表示阻塞等待。options为WNOHANG时表示非阻塞等待。简而言之阻塞等待就是等待子进程结束的过程中父进程不能运行。而非阻塞等待就是等待过程中父进程可以执行自己的代码。当参数为WNOHANG时waitpid会进行非阻塞轮询。等待结束返回0pid本次调用结束但子进程还没有退出返回0调用失败返回0。www.dongchedi.com/article/7600082197533737496www.dongchedi.com/article/7600081551585788478www.dongchedi.com/article/7600080627626836505www.dongchedi.com/article/7600076432072786494www.dongchedi.com/article/7600077785914540569www.dongchedi.com/article/7600076654119207449www.dongchedi.com/article/7600076084386021950www.dongchedi.com/article/7600077060547084862www.dongchedi.com/article/7600075783578763800www.dongchedi.com/article/7600075136489783833www.dongchedi.com/article/7600073513009529369www.dongchedi.com/article/7600074164837761598www.dongchedi.com/article/7600073368318542361www.dongchedi.com/article/7600073001341993534www.dongchedi.com/article/7600073974269329982www.dongchedi.com/article/7600074487064805912www.dongchedi.com/article/7600073227586683454www.dongchedi.com/article/7600069482082386457www.dongchedi.com/article/7600071292192260670www.dongchedi.com/article/7600069215726977561www.dongchedi.com/article/7600071094875537982www.dongchedi.com/article/7600070748635939353www.dongchedi.com/article/7600069587262308926www.dongchedi.com/article/7600069571290087961www.dongchedi.com/article/7600069625426395673www.dongchedi.com/article/7600069065444704793www.dongchedi.com/article/7600070228240138814www.dongchedi.com/article/7600069571290645017www.dongchedi.com/article/7600068352702448153www.dongchedi.com/article/7600069299780813374www.dongchedi.com/article/7600070076465070654www.dongchedi.com/article/7600070076464808510www.dongchedi.com/article/7600069722168148504www.dongchedi.com/article/7600068030437032510www.dongchedi.com/article/7600068903506723352www.dongchedi.com/article/7600069051742044697www.dongchedi.com/article/7600067161435980313www.dongchedi.com/article/7600067215119450648www.dongchedi.com/article/7600066283626922521www.dongchedi.com/article/7600067654162367000www.dongchedi.com/article/7600067338523640382www.dongchedi.com/article/7600061876546290238www.dongchedi.com/article/7600062394333037081www.dongchedi.com/article/7600064751125168702www.dongchedi.com/article/7600062857611199000www.dongchedi.com/article/7600064428301877822www.dongchedi.com/article/7600065673062187544www.dongchedi.com/article/7600061447326286360www.dongchedi.com/article/7600064204875727422www.dongchedi.com/article/7600063689303409214www.dongchedi.com/article/7600063881645883928www.dongchedi.com/article/7600061290274980376www.dongchedi.com/article/7600063037474652696​www.dongchedi.com/article/7600058391884956222www.dongchedi.com/article/7600058999849091609www.dongchedi.com/article/7600054609557619224www.dongchedi.com/article/7600058346296918590www.dongchedi.com/article/7600062930226741822