linux下文件操作函数小结(1)

一、不带缓存的文件I/O操作函数
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1.creat

Fuction:create a file.

Header file:
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>

Prototype:
int create(const char *pathname,mode_t mode);

Parameter:
pathname:the path of file.
mode:   S_I(R/W/X)(USER/GRP/OTH)
S_IRUSR:owner read right.
S_IWUSR:owner write right.
S_IXUSR:owner execute right.

S_IRGRP:group member ~
S_IWGRP:
S_IXGRP:

S_IROTH:others ~
S_IWOTH:
S_IXOTH:

Return value:
success:return 0
failed:return -1
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2.open

Function:open a exist file or create a new file.

Header file:
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>

Prototype:
int open(const char *pathname,int flags);
int open(const char *pathname,int flags,mode_t mode);

Parameter:
pathname:the path of file.
flags:
O_RDONLY:read only mode.
O_WRONLY:write mode.
O_RDWR:read and write mode.
O_APPEND:add to file end mode.
O_TRUNG:clean file to zero.
O_CREAT:create file.
O_EXCL:together with O_CREATE,if file exist,error.

Return value:
success:return a integer(file descriptor).
failed:return -1.
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3.close

Fuction:close the file.

Header file:
#include <unistd.h>

Prototype:
int close(int fd);

Parameter:
fd:file descriptor.

Return value:
success: return 0
failed:return -1
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4.read

Fuction:read the file.

Header file:#include <unistd.h>

Prototype:
ssize_t read(int fd,void *buf,size_t count);

Parameter:
fd:file descriptor.
buf:a point to buffer.
count:bytes of content.

Return value:
success:return the number of bytes read.
failed:return -1.
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5.write

Fuction:write to a file descriptor.

Header file:#include <unistd.h>

Prototype:
ssize_t write(int fd, const void *buf, size_t count);

Parameter:
fd:file descriptor.
buf:a point to buffer.
count:the max number of bytes write in.

Return value:
success:the number of bytes written.
failed:-1.
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