linux函數(shù)的阻塞與非阻塞IO及錯誤處理

1.阻塞是指進(jìn)程等待某一個(gè)事件的發(fā)生而處于等待狀態(tài)不往下執(zhí)行，如果等待的事件發(fā)生了則會繼續(xù)執(zhí)行該進(jìn)程。調(diào)用系統(tǒng)阻塞函數(shù)可能會導(dǎo)致進(jìn)程阻塞進(jìn)入睡眠狀態(tài)。

2.阻塞IO之read讀取鍵盤輸入數(shù)據(jù)

3.linux錯誤處理

###函數(shù)perro();r打印括號里的字符串和錯誤信息，全局變量errno會被賦值當(dāng)出現(xiàn)錯誤信息時(shí)，賦的值為下面的錯誤標(biāo)號

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###錯誤標(biāo)號及對應(yīng)錯誤

#define EPERM 1 /* Operation not permitted */ #define ENOENT 2 /* No such file or directory */ #define ESRCH 3 /* No such process */ #define EINTR 4 /* Interrupted system call */ #define EIO 5 /* I/O error */ #define ENXIO 6 /* No such device or address */ #define E2BIG 7 /* Argument list too long */ #define ENOEXEC 8 /* Exec format error */ #define EBADF 9 /* Bad file number */ #define ECHILD 10 /* No child processes */ #define EAGAIN 11 /* Try again */ #define ENOMEM 12 /* Out of memory */ #define EACCES 13 /* Permission denied */ #define EFAULT 14 /* Bad address */ #define ENOTBLK 15 /* Block device required */ #define EBUSY 16 /* Device or resource busy */ #define EEXIST 17 /* File exists */ #define EXDEV 18 /* Cross-device link */ #define ENODEV 19 /* No such device */ #define ENOTDIR 20 /* Not a directory */ #define EISDIR 21 /* Is a directory */ #define EINVAL 22 /* Invalid argument */ #define ENFILE 23 /* File table overflow */ #define EMFILE 24 /* Too many open files */ #define ENOTTY 25 /* Not a typewriter */ #define ETXTBSY 26 /* Text file busy */ #define EFBIG 27 /* File too large */ #define ENOSPC 28 /* No space left on device */ #define ESPIPE 29 /* Illegal seek */ #define EROFS 30 /* Read-only file system */ #define EMLINK 31 /* Too many links */ #define EPIPE 32 /* Broken pipe */ #define EDOM 33 /* Math argument out of domain of func */ #define ERANGE 34 /* Math result not representable */ #define EDEADLK 35 /* Resource deadlock would occur */ #define ENAMETOOLONG 36 /* File name too long */ #define ENOLCK 37 /* No record locks available */ #define ENOSYS 38 /* Function not implemented */ #define ENOTEMPTY 39 /* Directory not empty */ #define ELOOP 40 /* Too many symbolic links encountered */ #define EWOULDBLOCK EAGAIN /* Operation would block */ #define ENOMSG 42 /* No message of desired type */ #define EIDRM 43 /* Identifier removed */ #define ECHRNG 44 /* Channel number out of range */ #define EL2NSYNC 45 /* Level 2 not synchronized */ #define EL3HLT 46 /* Level 3 halted */ #define EL3RST 47 /* Level 3 reset */ #define ELNRNG 48 /* Link number out of range */ #define EUNATCH 49 /* Protocol driver not attached */ #define ENOCSI 50 /* No CSI structure available */ #define EL2HLT 51 /* Level 2 halted */ #define EBADE 52 /* Invalid exchange */ #define EBADR 53 /* Invalid request descriptor */ #define EXFULL 54 /* Exchange full */ #define ENOANO 55 /* No anode */ #define EBADRQC 56 /* Invalid request code */ #define EBADSLT 57 /* Invalid slot */#define EDEADLOCK EDEADLK#define EBFONT 59 /* Bad font file format */ #define ENOSTR 60 /* Device not a stream */ #define ENODATA 61 /* No data available */ #define ETIME 62 /* Timer expired */ #define ENOSR 63 /* Out of streams resources */ #define ENONET 66 /* Machine is not on the network */ #define ENOPKG 65 /* Package not installed */ #define EREMOTE 66 /* Object is remote */ #define ENOLINK 67 /* Link has been severed */ #define EADV 68 /* Advertise error */ #define ESRMNT 69 /* Srmount error */ #define ECOMM 70 /* Communication error on send */ #define EPROTO 71 /* Protocol error */ #define EMULTIHOP 72 /* Multihop attempted */ #define EDOTDOT 73 /* RFS specific error */ #define EBADMSG 74 /* Not a data message */ #define EOVERFLOW 75 /* Value too large for defined data type */ #define ENOTUNIQ 76 /* Name not unique on network */ #define EBADFD 77 /* File descriptor in bad state */ #define EREMCHG 78 /* Remote address changed */ #define ELIBACC 79 /* Can not access a needed shared library */ #define ELIBBAD 80 /* Accessing a corrupted shared library */ #define ELIBSCN 81 /* .lib section in a.out corrupted */ #define ELIBMAX 82 /* Attempting to link in too many shared libraries */ #define ELIBEXEC 83 /* Cannot exec a shared library directly */ #define EILSEQ 84 /* Illegal byte sequence */ #define ERESTART 85 /* Interrupted system call should be restarted */ #define ESTRPIPE 86 /* Streams pipe error */ #define EUSERS 87 /* Too many users */ #define ENOTSOCK 88 /* Socket operation on non-socket */ #define EDESTADDRREQ 89 /* Destination address required */ #define EMSGSIZE 90 /* Message too long */ #define EPROTOTYPE 91 /* Protocol wrong type for socket */ #define ENOPROTOOPT 92 /* Protocol not available */ #define EPROTONOSUPPORT 93 /* Protocol not supported */ #define ESOCKTNOSUPPORT 94 /* Socket type not supported */ #define EOPNOTSUPP 95 /* Operation not supported on transport endpoint */ #define EPFNOSUPPORT 96 /* Protocol family not supported */ #define EAFNOSUPPORT 97 /* Address family not supported by protocol */ #define EADDRINUSE 98 /* Address already in use */ #define EADDRNOTAVAIL 99 /* Cannot assign requested address */ #define ENETDOWN 100 /* Network is down */ #define ENETUNREACH 101 /* Network is unreachable */ #define ENETRESET 102 /* Network dropped connection because of reset */ #define ECONNABORTED 103 /* Software caused connection abort */ #define ECONNRESET 104 /* Connection reset by peer */ #define ENOBUFS 105 /* No buffer space available */ #define EISCONN 106 /* Transport endpoint is already connected */ #define ENOTCONN 107 /* Transport endpoint is not connected */ #define ESHUTDOWN 108 /* Cannot send after transport endpoint shutdown */ #define ETOOMANYREFS 109 /* Too many references: cannot splice */ #define ETIMEDOUT 110 /* Connection timed out */ #define ECONNREFUSED 111 /* Connection refused */ #define EHOSTDOWN 112 /* Host is down */ #define EHOSTUNREACH 113 /* No route to host */ #define EALREADY 114 /* Operation already in progress */ #define EINPROGRESS 115 /* Operation now in progress */ #define ESTALE 116 /* Stale NFS file handle */ #define EUCLEAN 117 /* Structure needs cleaning */ #define ENOTNAM 118 /* Not a XENIX named type file */ #define ENAVAIL 119 /* No XENIX semaphores available */ #define EISNAM 120 /* Is a named type file */ #define EREMOTEIO 121 /* Remote I/O error */ #define EDQUOT 122 /* Quota exceeded */#define ENOMEDIUM 123 /* No medium found */ #define EMEDIUMTYPE 124 /* Wrong medium type */ #define ECANCELED 125 /* Operation Canceled */ #define ENOKEY 126 /* Required key not available */ #define EKEYEXPIRED 127 /* Key has expired */ #define EKEYREVOKED 128 /* Key has been revoked */ #define EKEYREJECTED 129 /* Key was rejected by service */ /* for robust mutexes */ #define EOWNERDEAD 130 /* Owner died */ #define ENOTRECOVERABLE 131 /* State not recoverable */#define ERFKILL 132 /* Operation not possible due to RF-kill */#define EHWPOISON 133 /* Memory page has hardware error */

4.非阻塞IO讀取終端

5.lseek用來移動文件指針，打開文件時(shí)文件指針在文件開頭，有三個(gè)參數(shù)第一個(gè)為打開的文件描述符，第二個(gè)參數(shù)為文件指針位置偏移量的字節(jié)數(shù)，第三個(gè)參數(shù)為相對的偏移參考可以取三個(gè)參考值SEEK_SET文件開頭,SEEK_CUR文件當(dāng)前位置,SEEK_END文件末尾

####lseek拓展文件大小代碼，拓展文件一定要有一次寫的操作

#include<sys/types.h> #include<unistd.h> #include<errno.h> #include<sys/stat.h> #include<fcntl.h> #include<stdlib.h>int main(void) {int fd = open("ab",O_RDWR);if(fd < 0){perror("open file ab ");exit(-1);}lseek(fd,0x1000,SEEK_SET);write(fd,"a",1);close(fd);return 0;}

運(yùn)行效果查看0x1000就是4KB的偏移即就是4096外加1個(gè)字節(jié)就是文件大小4097

lseek也可以用來測量文件大小，將文件指針指向文件末尾，lseek的返回值就是文件開頭到文件指針處的偏移量

6.fcntl函數(shù)改變文件的訪問方式，針對打開的文件描述符，獲取文件打開標(biāo)記flag，也可以設(shè)置flag

fcntl的第二個(gè)參數(shù)可以選以下兩個(gè)值，分別為獲取文件訪問方式，設(shè)置文件訪問方式

7.ioctl用于控制設(shè)備，設(shè)置設(shè)備參數(shù)，設(shè)置或獲取設(shè)備文件的物理特性時(shí)使用ioctl函數(shù)，第一個(gè)參數(shù)是打開的文件描述符，第二個(gè)參數(shù)是設(shè)備請求碼,第三個(gè)是可變參數(shù)

##3例子第二個(gè)參數(shù)request要去驅(qū)動找，獲取屏幕尺寸存入size中

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posted on 2017-07-25 06:27 lovejobs 閱讀(...) 評論(...) 編輯 收藏

轉(zhuǎn)載于:https://www.cnblogs.com/huipengbo/p/7231966.html

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