ch3. file I/O

Advanced Programming in the UNIX Environment 책 start!!!

◆ open

#include<fcntl.h>

int open(const char *pathname, int oflag, .... /*mode_t mode*/);

(ret) success : file descriptor

        failed : -1

 

◆ creat

#include<fcntl.h>

int creat(const char *pathname, mode_t mode);

(ret) success : file descriptor (WRONLY) 

        failed : -1

 

◆ close

#include<unistd.h>

int close(int filedes);

(ret) success : 0

         faile : -1

 

◆ lseek

#include<unistd.h>

int lseek(int filedes, off_t offset, int whence);

(ret) success : new file offset

        failed : -1

 

#include<stdio.h> #include<stdlib.h> #include<unistd.h> int main(void) { if(lseek(STDIN_FILENO, 0, SEEK_CUR) == -1) { printf("cannot seek\n"); } else { printf("seek OK\n"); } exit(0); }

#include<fcntl.h> #include<stdio.h> #include<unistd.h> #include<stdlib.h> #include<sys/stat.h> #define FILE_MODE (S_IRUSR|S_IWUSR|S_IRGRP|S_IROTH) char buf1[] = "abcdefghij"; char buf2[] = "ABCDEFGHIJ"; int main(void) { int fd; if( ( fd = creat("file.hole",FILE_MODE)) < 0 ) { printf("creat() error!\n"); exit(1); } if (write(fd, buf1, 10) != 10) { printf(" write() error!\n"); exit(1); } if( lseek(fd,16384, SEEK_SET) == -1) { printf(" lseek() error!\n"); exit(1); } if(write(fd, buf2,10)!= 10) { printf(" write() error!\n"); exit(1); } exit(0); }

 

◆ read

#include<unistd.h>

ssize_t read(int filedes, void *buf, size_t nbytes); 

(ret) success :  number of byte read , end of file : 0 

        failed : -1 

◆ write

#include<unistd.h>

ssize_t write(int filedes, const void *buf, size_t nbytes); 

(ret) success : number of byte written 

                       failed : -1

#include<stdio.h> #include<stdlib.h> #include<unistd.h> #define BUFSIZE 20 int main(void) { char buf[BUFSIZE]; int nbytes; nbytes = read(0,buf,BUFSIZE); write(1,buf,nbytes); return 0; }

◆ pread

#include<unistd.h>

 ssize_t pread(int filedes, void *buf, size_t nbytes, off_t offset);

(ret) success :  읽은 바이트 수, 파일 끝이면 0

                       failed : -1

 

◆ pwrite

#include<unistd.h>

 ssize_t pwrite(int filedes, const void *buf, size_t nbytes, off_t offset); 

(ret) success :  기록된 바이트 수

                       failed : -1

 

◆ dup

#include<unistd.h>

 int dup(int filedes);

(ret) success :  새 파일 디스크립터

                       failed : -1

 

◆ dup2

#include<unistd.h>

 int dup2(int filedes, int filedes2);

(ret)  success :  새 파일 디스크립터

                       failed : -1

 

◆ sync

#include<unistd.h>

 void sync(void);

 

◆ fsync

#include<unistd.h>

 int fsync(int filedes);

(ret)  success :  0

                       failed : -1

 

◆ fdatasync

#include<unistd.h>

 int fdatasync(int filedes);

(ret)  success :  0

                       failed : -1

 

◆ fcntl

#include<fcntl.h>

 int fcntl(int filedes, int cmd, .../*int arg*/);

(ret)  success :  성공 시 cmd에 따라 다름

                       failed : -1

#include<stdio.h> #include<stdlib.h> #include<fcntl.h> #include<sys/stat.h> int main(int argc, char *argv[]) { int val; if(argc != 2) { printf("usage : a.out <descriptor #>"); exit(1); } if((val = fcntl(atoi(argv[1]), F_GETFL, 0)) <0 ) { printf("fcntl error for fd %d", atoi(argv[1])); exit(1); } switch(val & O_ACCMODE) { case O_RDONLY: printf("read only"); break; case O_WRONLY: printf("write only"); break; case O_RDWR: printf("read write"); break; default: printf("unknown access mode"); exit(1); } if(val & O_APPEND) printf(", append"); if(val & O_NONBLOCK) printf(", nonblocking"); #if defined(O_SYNC) if(val & O_SYNC) printf(", synchronous writes"); #endif #if !defined(_POSIX_C_SOURCE) && defined(O_FSYNC) if(val&O_FSYNC) printf(", synchronous writes"); #endif putchar('\n'); exit(0); }

#include<stdio.h> #include<stdlib.h> #include<fcntl.h> void set_fl(int fd, int flags)/*flags are file status flags to turn on*/ { int val; if((val = fcntl(fd, F_GETFL, 0)) < 0) { printf("fcntl F_GETFL error"); exit(1); } val |= flags; /* turn on flags */ if(fcntl(fd, F_SETFL, val) < 0) { printf("fcntl F_SETFL error"); exit(1); } }

◆ ioctl

#include<unistd.h>

#include<sys/ioctl.h>

#include<stropts.h>

int ioctl(int filedes, int request, ...);

(ret)  success :  -1 이외의 값

                       failed : -1